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ABS CGSO practice questions

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Question 1Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which serum tumor marker is most appropriately used to monitor response to therapy in a patient with newly diagnosed testicular seminoma?

  1. Carcinoembryonic antigen (CEA)
  2. Beta-human chorionic gonadotropin (beta-hCG) Correct answer.
  3. CA 19-9
  4. Alpha-fetoprotein (AFP)

Explanation

Pure seminomas may secrete beta-hCG but never AFP; elevation of AFP implies a nonseminomatous component. Beta-hCG is therefore used for monitoring seminoma burden and treatment response. CA 19-9 and CEA are markers of gastrointestinal and other adenocarcinomas, not germ cell tumors.

Question 2Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 3-year-old child presents with a large abdominal mass, and imaging shows a kidney tumor. Which histologic finding is most characteristic of Wilms tumor?

  1. Spindle cells with skeletal muscle differentiation and t(2;13)
  2. Triphasic pattern of blastemal, epithelial, and stromal elements Correct answer.
  3. Nests of cells with clear cytoplasm and a delicate vascular network
  4. Small round blue cells with Homer Wright rosettes

Explanation

Wilms tumor (nephroblastoma) classically shows a triphasic histology of blastema, epithelium, and stroma. This triphasic pattern reflects its origin from metanephric mesenchyme. The other options describe neuroblastoma, clear cell renal carcinoma, and alveolar rhabdomyosarcoma respectively.

Question 3Diagnosis of cancer, including complex presentations and rare or unusual cancers

A patient with long-standing Barrett esophagus is found to have high-grade dysplasia. Which molecular event is most strongly associated with progression from Barrett esophagus to esophageal adenocarcinoma?

  1. Inactivation of CDKN2A and TP53 with accumulation of genomic instability Correct answer.
  2. Amplification of MYCN
  3. Germline mutation of RB1
  4. Activation of the ETV6-NTRK3 fusion

Explanation

Progression of Barrett esophagus to adenocarcinoma follows a sequence of CDKN2A loss, TP53 mutation, and increasing genomic instability. These events drive clonal evolution through dysplasia to invasive cancer. The other options describe fusions and mutations typical of secretory breast carcinoma, retinoblastoma, and neuroblastoma.

Question 4Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 55-year-old man has a 6 cm retroperitoneal mass with elevated AFP and beta-hCG. Biopsy shows mixed elements. Which diagnosis is most consistent with these findings?

  1. Pure seminoma
  2. Nonseminomatous germ cell tumor Correct answer.
  3. Leydig cell tumor
  4. Primary retroperitoneal liposarcoma

Explanation

Elevation of AFP indicates a nonseminomatous component, and mixed histology with both markers supports a nonseminomatous germ cell tumor. Pure seminoma does not produce AFP. Leydig cell tumors and liposarcomas do not secrete these germ cell markers.

Question 5Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which clinical feature most strongly suggests that a childhood abdominal mass is a neuroblastoma rather than a Wilms tumor?

  1. Hematuria and hypertension
  2. Association with hemihypertrophy
  3. Calcification on imaging with elevated urinary catecholamines Correct answer.
  4. Smooth well-encapsulated renal mass

Explanation

Neuroblastoma typically shows calcification, elevated urinary catecholamines (VMA/HVA), and often crosses the midline. Wilms tumor tends to be a smooth intrarenal mass and may be associated with hemihypertrophy syndromes. Hematuria and hypertension are more typical of renal tumors.

Question 6Diagnosis of cancer, including complex presentations and rare or unusual cancers

A patient has a metastatic adenocarcinoma of unknown primary. Which immunohistochemical profile most supports a diagnosis of colorectal origin?

  1. CK7 negative, CK20 negative, S100 positive
  2. CK7 positive, CK20 positive, TTF-1 positive
  3. CK7 negative, CK20 positive, CDX2 positive Correct answer.
  4. CK7 positive, CK20 negative, CDX2 negative

Explanation

Colorectal adenocarcinoma typically expresses CK20 and CDX2 while being CK7 negative. This pattern helps localize adenocarcinomas of unknown primary. TTF-1 positivity suggests lung or thyroid origin, and S100 suggests melanoma or neural tumors.

Question 7Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which paraneoplastic syndrome is most classically associated with small cell lung cancer?

  1. Ectopic ACTH secretion causing Cushing syndrome Correct answer.
  2. Hypercalcemia from parathyroid hormone-related peptide
  3. Hypoglycemia from insulin-like growth factor
  4. Polycythemia from erythropoietin production

Explanation

Small cell lung cancer is a classic cause of ectopic ACTH secretion and Cushing syndrome, along with SIADH and Lambert-Eaton syndrome. Hypercalcemia from PTHrP is more typical of squamous cell carcinoma of the lung. Polycythemia and IGF-mediated hypoglycemia are associated with renal and hepatic tumors.

Question 8Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 30-year-old woman has a thyroid nodule. Fine needle aspiration shows cells with nuclear grooves, pseudoinclusions, and Orphan Annie eye nuclei. What is the most likely diagnosis?

  1. Anaplastic thyroid carcinoma
  2. Follicular carcinoma
  3. Medullary thyroid carcinoma
  4. Papillary thyroid carcinoma Correct answer.

Explanation

Nuclear grooves, intranuclear pseudoinclusions, and optically clear Orphan Annie eye nuclei are the hallmark cytologic features of papillary thyroid carcinoma. Medullary carcinoma shows amyloid and calcitonin positivity, while anaplastic carcinoma shows high-grade pleomorphic cells. Follicular carcinoma is diagnosed by capsular or vascular invasion, not nuclear features.

Question 9Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which finding best distinguishes follicular carcinoma from follicular adenoma of the thyroid?

  1. Positive calcitonin immunostain
  2. Elevated serum thyroglobulin
  3. Capsular or vascular invasion on histology Correct answer.
  4. Presence of nuclear pseudoinclusions

Explanation

Follicular adenoma and carcinoma can look identical on cytology; the distinction depends on demonstrating capsular or vascular invasion on surgical histology. Nuclear pseudoinclusions indicate papillary carcinoma, and calcitonin points to medullary carcinoma. Serum thyroglobulin is not reliable for this distinction.

Question 10Diagnosis of cancer, including complex presentations and rare or unusual cancers

A patient with a pancreatic head mass has a serum marker that is useful for monitoring but not for screening. Which marker is this?

  1. CA 19-9 Correct answer.
  2. Beta-hCG
  3. Alpha-fetoprotein
  4. CA 125

Explanation

CA 19-9 is commonly elevated in pancreatic adenocarcinoma and is used to monitor disease and response to therapy, but it lacks sensitivity and specificity for screening. CA 125 is used in ovarian cancer, and AFP and beta-hCG are germ cell markers.

Question 11Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which cancer is most strongly associated with chronic infection by Epstein-Barr virus?

  1. Cervical squamous cell carcinoma
  2. Nasopharyngeal carcinoma Correct answer.
  3. Kaposi sarcoma
  4. Hepatocellular carcinoma

Explanation

Epstein-Barr virus is strongly associated with undifferentiated nasopharyngeal carcinoma, as well as Burkitt lymphoma and some lymphomas. Cervical carcinoma is linked to human papillomavirus, hepatocellular carcinoma to hepatitis B and C, and Kaposi sarcoma to human herpesvirus 8.

Question 12Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 25-year-old man has mediastinal widening and gynecomastia. Biopsy shows a germ cell tumor. Which tumor type most commonly arises in the anterior mediastinum of young men and can secrete beta-hCG?

  1. Thymoma
  2. Mediastinal teratoma with malignant transformation
  3. Primary mediastinal large B-cell lymphoma
  4. Nonseminomatous mediastinal germ cell tumor Correct answer.

Explanation

Primary mediastinal nonseminomatous germ cell tumors occur in young men, often secrete beta-hCG or AFP, and can cause gynecomastia through hCG-driven estrogen production. Thymomas and lymphomas do not secrete these markers. Mature teratomas are usually marker-negative.

Question 13Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which feature is most characteristic of anaplastic thyroid carcinoma?

  1. Bilateral multifocal encapsulated nodules
  2. Association with elevated calcitonin
  3. Indolent growth over many years
  4. Rapidly enlarging mass with local invasion and distant spread Correct answer.

Explanation

Anaplastic thyroid carcinoma is an aggressive, rapidly growing tumor with extensive local invasion and early metastasis, often in older patients. It is undifferentiated and does not produce calcitonin. Indolent growth and multifocal encapsulated nodules are more typical of well-differentiated thyroid tumors.

Question 14Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which inherited syndrome carries the highest risk of developing medullary thyroid carcinoma?

  1. Li-Fraumeni syndrome
  2. Von Hippel-Lindau disease
  3. Familial adenomatous polyposis
  4. Multiple endocrine neoplasia type 2 Correct answer.

Explanation

Multiple endocrine neoplasia type 2 is caused by germline RET mutations and predisposes to medullary thyroid carcinoma, pheochromocytoma, and hyperparathyroidism. Li-Fraumeni involves TP53 and predisposes to sarcomas and breast cancer, while FAP and VHL predispose to colorectal and renal tumors respectively.

Question 15Diagnosis of cancer, including complex presentations and rare or unusual cancers

A patient presents with a painless testicular mass. Ultrasound shows a homogeneous hypoechoic lesion, and serum AFP is normal with slightly elevated beta-hCG. Orchiectomy reveals sheets of uniform cells with clear cytoplasm and prominent nucleoli, with fibrous septa containing lymphocytes. What is the most likely diagnosis?

  1. Classic seminoma Correct answer.
  2. Choriocarcinoma
  3. Embryonal carcinoma
  4. Yolk sac tumor

Explanation

Classic seminoma presents as a homogeneous mass with uniform cells, clear cytoplasm, prominent nucleoli, and fibrous septa infiltrated by lymphocytes. AFP is normal, and beta-hCG may be mildly elevated. Embryonal carcinoma and yolk sac tumors are AFP-associated, and choriocarcinoma causes marked beta-hCG elevation with hemorrhage.

Question 16Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which molecular abnormality is characteristic of Burkitt lymphoma?

  1. t(9;22) involving BCR-ABL1
  2. t(14;18) involving BCL2
  3. t(8;14) involving MYC Correct answer.
  4. t(11;14) involving CCND1

Explanation

Burkitt lymphoma is characterized by translocations involving MYC on chromosome 8, most commonly t(8;14). This drives constitutive MYC expression and rapid proliferation. BCR-ABL1 defines chronic myeloid leukemia, BCL2 translocation defines follicular lymphoma, and CCND1 translocation defines mantle cell lymphoma.

Question 17Diagnosis of cancer, including complex presentations and rare or unusual cancers

A patient with a history of treated breast cancer presents with a solitary brain metastasis. Which feature most strongly suggests the metastasis is from breast rather than a primary brain tumor?

  1. Infiltrative lesion crossing the corpus callosum
  2. Ring-enhancing lesion with surrounding edema
  3. Well-demarcated gray-white lesion at the gray-white junction Correct answer.
  4. Cystic lesion with a mural nodule in the cerebellum

Explanation

Metastases typically lodge at the gray-white junction where vessel caliber changes, forming well-demarcated multiple or solitary lesions. Infiltrative lesions crossing the corpus callosum (butterfly pattern) suggest glioblastoma. Cystic cerebellar lesions with a mural nodule suggest hemangioblastoma, and ring enhancement with edema is nonspecific.

Question 18Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which finding on immunohistochemistry supports a diagnosis of hepatocellular carcinoma in a liver mass?

  1. CK20 and CDX2 positivity
  2. HepPar-1 and arginase-1 positivity Correct answer.
  3. TTF-1 positivity
  4. Synaptophysin and chromogranin positivity

Explanation

Hepatocellular carcinoma expresses hepatocyte markers such as HepPar-1 and arginase-1. TTF-1 indicates lung or thyroid origin, CDX2 indicates colorectal origin, and neuroendocrine markers indicate a neuroendocrine tumor. These markers help distinguish primary liver tumors from metastases.

Question 19Diagnosis of cancer, including complex presentations and rare or unusual cancers

A child presents with a posterior fossa mass. Which tumor type is most common in this location during childhood?

  1. Meningioma
  2. Pituitary adenoma
  3. Medulloblastoma Correct answer.
  4. Glioblastoma

Explanation

Medulloblastoma is the most common malignant posterior fossa tumor in children, arising in the cerebellum. Glioblastoma, meningioma, and pituitary adenoma occur predominantly in adults and in different locations. This reflects the distinct epidemiology of pediatric brain tumors.

Question 20Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which paraneoplastic neurologic syndrome is most strongly associated with anti-Hu antibodies in small cell lung cancer?

  1. Cerebellar ataxia from anti-Yo
  2. Lambert-Eaton myasthenic syndrome
  3. Opsoclonus-myoclonus in children
  4. Sensory neuronopathy Correct answer.

Explanation

Anti-Hu antibodies are associated with paraneoplastic sensory neuronopathy and encephalomyelitis, most often with small cell lung cancer. Lambert-Eaton syndrome is associated with voltage-gated calcium channel antibodies, anti-Yo with gynecologic cancers, and opsoclonus-myoclonus with neuroblastoma.

Question 21Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 60-year-old smoker has a lung mass. Biopsy shows keratin pearls and intercellular bridges. Which type of lung carcinoma is this?

  1. Squamous cell carcinoma Correct answer.
  2. Small cell carcinoma
  3. Adenocarcinoma
  4. Large cell carcinoma

Explanation

Keratin pearls and intercellular bridges are hallmarks of squamous cell carcinoma of the lung. Adenocarcinoma shows glandular formation and mucin production. Small cell carcinoma shows small cells with scant cytoplasm and neuroendocrine markers, and large cell carcinoma is a diagnosis of exclusion.

Question 22Diagnosis of cancer, including complex presentations and rare or unusual cancers

A patient has a history of colorectal cancer and now has a solitary liver lesion. Which molecular marker on the liver biopsy would most support a colorectal metastasis?

  1. HepPar-1 positivity
  2. TTF-1 positivity
  3. CDX2 positivity Correct answer.
  4. Melan-A positivity

Explanation

CDX2 is a homeobox transcription factor expressed in intestinal epithelium and is a sensitive marker for colorectal adenocarcinoma. HepPar-1 indicates hepatocellular origin, TTF-1 lung or thyroid, and Melan-A melanocytic differentiation. This panel helps confirm the origin of a liver metastasis.

Question 23Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which feature is most characteristic of a desmoid tumor (aggressive fibromatosis)?

  1. Locally infiltrative proliferation of uniform fibroblasts without metastasis Correct answer.
  2. Tumor with a t(X;18) translocation
  3. High-grade pleomorphic cells with frequent mitoses and metastasis
  4. Biphasic pattern with epithelial and stromal elements

Explanation

Desmoid tumors are locally aggressive fibroblastic proliferations that infiltrate surrounding tissue and recur but do not metastasize. High-grade pleomorphic sarcomas and synovial sarcoma (t(X;18)) behave differently. A biphasic pattern describes synovial sarcoma or fibroadenoma.

Question 24Diagnosis of cancer, including complex presentations and rare or unusual cancers

A patient with suspected pancreatic adenocarcinoma has a CA 19-9 level that is normal. Which factor most commonly explains a falsely normal CA 19-9 in this setting?

  1. Recent corticosteroid use
  2. Lewis antigen-negative blood group Correct answer.
  3. Elevated bilirubin
  4. Renal failure

Explanation

CA 19-9 synthesis requires the Lewis blood group antigen; individuals who are Lewis antigen-negative cannot produce CA 19-9 and will have falsely low or normal levels. Bilirubin elevation tends to raise CA 19-9, and corticosteroid use and renal failure are not classic causes of false-negative results.

Question 25Diagnosis of cancer, including complex presentations and rare or unusual cancers

Which tumor is most strongly associated with human herpesvirus 8 (HHV-8) infection?

  1. Hepatocellular carcinoma
  2. Merkel cell carcinoma
  3. Kaposi sarcoma Correct answer.
  4. Nasopharyngeal carcinoma

Explanation

HHV-8, also called Kaposi sarcoma-associated herpesvirus, is the causative agent of Kaposi sarcoma, particularly in immunocompromised patients. Nasopharyngeal carcinoma is linked to EBV, hepatocellular carcinoma to hepatitis B and C, and Merkel cell carcinoma to Merkel cell polyomavirus.

Question 26Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 55-year-old man presents with a solitary bone lesion. Biopsy shows malignant plasma cells. Which laboratory finding is most characteristic of this disease?

  1. Elevated serum calcitonin
  2. A monoclonal M protein spike on serum electrophoresis Correct answer.
  3. Elevated serum alpha-fetoprotein
  4. Positive anti-double-stranded DNA antibody

Explanation

Multiple myeloma is a clonal plasma cell neoplasm that typically secretes a monoclonal immunoglobulin detectable as an M spike on serum or urine electrophoresis. Alpha-fetoprotein, anti-dsDNA, and calcitonin are markers of germ cell tumors, systemic lupus, and medullary thyroid carcinoma respectively.

Question 27Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 62-year-old woman has a pigmented skin lesion with irregular borders and color variegation. Which histologic feature most strongly supports a diagnosis of melanoma?

  1. Atypical melanocytes with pagetoid spread into the epidermis Correct answer.
  2. Uniform small melanocytes with no atypia
  3. Nests of melanocytes confined to the epidermis
  4. Keratin-filled cysts within the dermis

Explanation

Melanoma is characterized by atypical melanocytes showing pagetoid (intraepidermal) spread, irregular nesting, and cytologic atypia. Benign nevi have orderly nests confined to the dermoepidermal junction and lack pagetoid scatter.

Question 28Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 45-year-old man has a large anterior mediastinal mass. Biopsy shows a neoplasm arising from thymic epithelial cells. Which paraneoplastic syndrome is most commonly associated with thymoma?

  1. Cushing syndrome from ectopic ACTH
  2. Hypercalcemia from PTHrP
  3. Carcinoid syndrome
  4. Myasthenia gravis Correct answer.

Explanation

Thymomas are strongly associated with myasthenia gravis, occurring in a substantial minority of patients through an autoimmune mechanism. Carcinoid syndrome, ectopic ACTH, and PTHrP-mediated hypercalcemia are associated with other tumors such as carcinoid, small cell lung cancer, and squamous cell carcinoma.

Question 29Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 70-year-old man has painless gross hematuria. Cystoscopy shows a papillary bladder mass. Which histologic type accounts for most bladder cancers in industrialized countries?

  1. Small cell carcinoma
  2. Squamous cell carcinoma
  3. Adenocarcinoma
  4. Urothelial (transitional cell) carcinoma Correct answer.

Explanation

Urothelial carcinoma is by far the most common histologic type of bladder cancer in industrialized nations, typically presenting as painless hematuria. Squamous cell carcinoma is more common in regions with schistosomiasis, and adenocarcinoma and small cell carcinoma are rare.

Question 30Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 58-year-old woman has a renal mass. Biopsy shows a tumor composed of cells with clear cytoplasm and a prominent delicate vascular network. Which renal cell carcinoma subtype does this most likely represent?

  1. Collecting duct carcinoma
  2. Papillary renal cell carcinoma
  3. Chromophobe renal cell carcinoma
  4. Clear cell renal cell carcinoma Correct answer.

Explanation

Clear cell renal cell carcinoma is the most common subtype and is characterized by cells with optically clear cytoplasm due to glycogen and lipid content, arranged in nests with a delicate branching vasculature. Papillary, chromophobe, and collecting duct carcinomas have different architectural and cytologic features.

Question 31Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 35-year-old woman has a large ovarian mass. Pathology shows a tumor with areas of cartilage, hair, and respiratory epithelium. Which diagnosis is most likely?

  1. Granulosa cell tumor
  2. Immature teratoma
  3. Mature cystic teratoma Correct answer.
  4. Mucinous cystadenocarcinoma

Explanation

Mature cystic teratomas (dermoid cysts) contain well-differentiated tissues from multiple germ layers, including skin, hair, cartilage, and respiratory epithelium. Immature teratomas contain primitive neuroectodermal tissue and are malignant, while mucinous and granulosa cell tumors lack this mixed mature tissue pattern.

Question 32Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 50-year-old man with a history of gastroesophageal reflux has a distal esophageal mass. Biopsy shows intestinal-type epithelium with goblet cells adjacent to adenocarcinoma. Which precursor lesion is this?

  1. Squamous papilloma
  2. Esophageal varices
  3. Achalasia
  4. Barrett esophagus Correct answer.

Explanation

Barrett esophagus is intestinal metaplasia of the distal esophagus, characterized by goblet cells, and is the major precursor lesion for esophageal adenocarcinoma. Squamous papillomas, varices, and achalasia are not premalignant intestinal metaplastic lesions.

Question 33Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 68-year-old man has a slow-growing mass in the parotid gland. Fine needle aspiration shows a biphasic tumor with epithelial and myoepithelial cells in a chondromyxoid stroma. Which diagnosis is most likely?

  1. Pleomorphic adenoma Correct answer.
  2. Mucoepidermoid carcinoma
  3. Warthin tumor
  4. Acinic cell carcinoma

Explanation

Pleomorphic adenoma is the most common salivary gland tumor and shows a biphasic proliferation of epithelial and myoepithelial cells within a chondromyxoid stroma. Mucoepidermoid carcinoma, Warthin tumor, and acinic cell carcinoma have distinct histologic patterns.

Question 34Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 40-year-old man has a destructive midline nasal mass. Biopsy shows an angiocentric, angiodestructive proliferation of atypical lymphoid cells. Which diagnosis is most likely?

  1. Nasopharyngeal carcinoma
  2. Diffuse large B-cell lymphoma
  3. Wegener granulomatosis
  4. Extranodal NK/T-cell lymphoma, nasal type Correct answer.

Explanation

Extranodal NK/T-cell lymphoma, nasal type, classically presents as a destructive midline facial lesion with angiocentric and angiodestructive atypical lymphoid infiltrates and is associated with Epstein-Barr virus. Diffuse large B-cell lymphoma and nasopharyngeal carcinoma do not show this angiocentric pattern, and Wegener granulomatosis is an inflammatory vasculitis.

Question 35Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 60-year-old woman has a painless neck mass. Biopsy shows a tumor composed of cells with abundant eosinophilic granular cytoplasm and prominent nucleoli, arising from thyroid follicular cells. Which diagnosis is most likely?

  1. Papillary thyroid carcinoma
  2. Medullary thyroid carcinoma
  3. Follicular adenoma
  4. Hurthle cell (oncocytic) carcinoma Correct answer.

Explanation

Hurthle cell (oncocytic) carcinoma is a thyroid follicular cell neoplasm composed of cells with abundant eosinophilic granular cytoplasm due to mitochondrial accumulation. Papillary carcinoma shows nuclear features such as grooves and pseudoinclusions, and medullary carcinoma arises from parafollicular C cells.

Question 36Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 22-year-old man has a testicular mass. Serum human chorionic gonadotropin is markedly elevated. Which germ cell tumor component is most likely present?

  1. Choriocarcinoma Correct answer.
  2. Teratoma
  3. Seminoma
  4. Yolk sac tumor

Explanation

Choriocarcinoma is a germ cell tumor composed of trophoblastic tissue that secretes large amounts of human chorionic gonadotropin. Yolk sac tumors secrete alpha-fetoprotein, and seminomas and teratomas do not produce marked hCG elevation.

Question 37Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 65-year-old man has a lung mass with neuroendocrine features. Which immunohistochemical marker is most useful in confirming a neuroendocrine origin?

  1. Synaptophysin Correct answer.
  2. Cytokeratin 7
  3. Vimentin
  4. CD45

Explanation

Synaptophysin is a neuroendocrine marker useful in confirming neuroendocrine differentiation in tumors such as small cell carcinoma and carcinoid. Cytokeratin 7 marks epithelial cells, vimentin marks mesenchymal cells, and CD45 is a leukocyte marker.

Question 38Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 55-year-old woman has a hepatic mass. Biopsy shows a tumor with trabecular architecture, bile production, and elevated serum alpha-fetoprotein. Which risk factor is most strongly associated with this tumor?

  1. Chronic hepatitis B infection Correct answer.
  2. Oral contraceptive use
  3. Hemochromatosis treated with phlebotomy
  4. Primary biliary cholangitis

Explanation

Hepatocellular carcinoma is strongly associated with chronic hepatitis B and C infection, which cause cirrhosis and chronic hepatocyte proliferation. Primary biliary cholangitis and treated hemochromatosis are less strongly associated, and oral contraceptives predispose to hepatic adenomas rather than carcinoma.

Question 39Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 70-year-old man has a slowly enlarging skin lesion on the face. Biopsy shows basaloid cells with peripheral palisading and clefting between tumor nests and stroma. Which diagnosis is most likely?

  1. Squamous cell carcinoma
  2. Merkel cell carcinoma
  3. Basal cell carcinoma Correct answer.
  4. Sebaceous carcinoma

Explanation

Basal cell carcinoma is characterized by nests of basaloid cells with peripheral palisading and retraction artifact (clefting) between the tumor and surrounding stroma. Squamous cell carcinoma shows keratinization, and Merkel cell carcinoma is a neuroendocrine tumor.

Question 40Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 48-year-old woman has a colon mass. Biopsy shows a poorly differentiated carcinoma with signet-ring cells and abundant extracellular mucin. Which molecular pathway is most strongly associated with this histologic pattern?

  1. NTRK gene fusion
  2. BRAF V600E mutation with CpG island methylator phenotype
  3. Microsatellite instability with DNA mismatch repair deficiency Correct answer.
  4. Adenomatous polyposis coli (APC) mutation with chromosomal instability

Explanation

Signet-ring cell and mucinous colorectal carcinomas are more frequently associated with the microsatellite instability pathway due to DNA mismatch repair deficiency, particularly in right-sided tumors. The APC/chromosomal instability pathway is more typical of conventional adenocarcinomas.

Question 41Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 30-year-old woman has a cystic pancreatic mass. Aspiration shows mucin and elevated carcinoembryonic antigen. Which diagnosis is most likely?

  1. Pancreatic neuroendocrine tumor
  2. Serous cystadenoma
  3. Solid pseudopapillary neoplasm
  4. Mucinous cystic neoplasm Correct answer.

Explanation

Mucinous cystic neoplasms of the pancreas are cystic lesions lined by mucin-producing epithelium and are associated with elevated cyst fluid carcinoembryonic antigen. Serous cystadenomas have glycogen-rich clear cells, and solid pseudopapillary neoplasms are solid and cystic but not mucinous.

Question 42Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 65-year-old man has a lytic bone lesion and hypercalcemia. Biopsy shows a malignant neoplasm of plasma cells. Which finding on serum protein electrophoresis most supports the diagnosis?

  1. Elevated alpha-1 antitrypsin
  2. Absence of any protein band
  3. Polyclonal hypergammaglobulinemia
  4. A narrow monoclonal band in the gamma region Correct answer.

Explanation

Multiple myeloma is characterized by a monoclonal immunoglobulin produced by the neoplastic plasma cell clone, appearing as a narrow band on serum protein electrophoresis. Polyclonal hypergammaglobulinemia reflects a reactive process, and alpha-1 antitrypsin is unrelated.

Question 43Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 50-year-old woman has a thyroid mass. Biopsy shows a neoplasm composed of C cells with amyloid stroma. Which serum marker is most useful for monitoring this tumor?

  1. Thyroglobulin
  2. Thyroid-stimulating hormone
  3. Calcitonin Correct answer.
  4. Thyroid peroxidase antibody

Explanation

Medullary thyroid carcinoma arises from calcitonin-secreting parafollicular C cells, and serum calcitonin is the tumor marker used for monitoring. Thyroglobulin monitors differentiated follicular-derived carcinomas, and TSH and thyroid peroxidase antibodies assess thyroid function and autoimmunity.

Question 44Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 60-year-old man has a painless scrotal mass. Ultrasound shows a solid testicular lesion. Which serum marker is most useful in the initial evaluation of a suspected germ cell tumor?

  1. Carcinoembryonic antigen
  2. Alpha-fetoprotein and human chorionic gonadotropin Correct answer.
  3. CA 125
  4. Prostate-specific antigen

Explanation

Alpha-fetoprotein and human chorionic gonadotropin are the standard serum markers used in the initial evaluation and monitoring of testicular germ cell tumors. CA 125 is used for ovarian tumors, CEA for colorectal and other adenocarcinomas, and PSA for prostate cancer.

Question 45Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 45-year-old woman has a retroperitoneal mass. Biopsy shows a tumor with lipoblasts and mature adipocytes. Which diagnosis is most likely?

  1. Gastrointestinal stromal tumor
  2. Liposarcoma Correct answer.
  3. Lipoma
  4. Leiomyosarcoma

Explanation

Liposarcoma is a malignant adipocytic tumor characterized by lipoblasts, and it commonly arises in the retroperitoneum. Lipomas lack lipoblasts and atypia, while leiomyosarcomas and GISTs show smooth muscle or interstitial cell differentiation.

Question 46Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 35-year-old man has a painless neck mass. Biopsy shows a tumor with keratinizing squamous epithelium and abundant lymphoid tissue. Which diagnosis is most likely?

  1. Metastatic squamous cell carcinoma Correct answer.
  2. Warthin tumor
  3. Branchial cleft cyst
  4. Thyroglossal duct cyst

Explanation

A neck mass with keratinizing squamous epithelium and lymphoid tissue in an adult should raise concern for metastatic squamous cell carcinoma, often from an occult head and neck primary. Branchial cleft cysts are developmental and lack malignant squamous atypia.

Question 47Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 55-year-old woman has a breast mass. Biopsy shows a tumor with cells that have lost E-cadherin expression and infiltrate in single files. Which diagnosis is most likely?

  1. Tubular carcinoma
  2. Medullary carcinoma
  3. Invasive ductal carcinoma, no special type
  4. Invasive lobular carcinoma Correct answer.

Explanation

Invasive lobular carcinoma is characterized by loss of E-cadherin, causing cells to infiltrate in single files rather than forming cohesive ducts. Invasive ductal carcinoma, medullary carcinoma, and tubular carcinoma retain E-cadherin and form cohesive structures.

Question 48Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 60-year-old man has a lung mass. Biopsy shows a tumor with small blue cells, scant cytoplasm, and frequent mitoses. Which immunohistochemical finding is most characteristic?

  1. Dot-like perinuclear cytokeratin positivity with neuroendocrine markers Correct answer.
  2. S100 positivity
  3. Strong diffuse cytokeratin 5/6 positivity
  4. CD45 positivity

Explanation

Small cell lung carcinoma shows dot-like perinuclear cytokeratin positivity along with neuroendocrine markers such as synaptophysin and chromogranin. Cytokeratin 5/6 is typical of squamous cell carcinoma, CD45 marks lymphocytes, and S100 marks melanocytic and neural tumors.

Question 49Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 40-year-old woman has a thyroid nodule and a family history of thyroid cancer. Genetic testing reveals a RET proto-oncogene mutation. Which syndrome should be suspected?

  1. Li-Fraumeni syndrome
  2. Cowden syndrome
  3. Multiple endocrine neoplasia type 2 Correct answer.
  4. Multiple endocrine neoplasia type 1

Explanation

Germline RET proto-oncogene mutations cause multiple endocrine neoplasia type 2, which includes medullary thyroid carcinoma, pheochromocytoma, and hyperparathyroidism. MEN1 is caused by MEN1 gene mutations, and Cowden and Li-Fraumeni syndromes involve PTEN and TP53 mutations respectively.

Question 50Diagnosis of cancer, including complex presentations and rare or unusual cancers

A 50-year-old man has a painless testicular mass. Biopsy shows a uniform population of large cells with clear cytoplasm and prominent nucleoli, with fibrous septa containing lymphocytes. Which diagnosis is most likely?

  1. Seminoma Correct answer.
  2. Yolk sac tumor
  3. Leydig cell tumor
  4. Embryonal carcinoma

Explanation

Seminoma is characterized by uniform large cells with clear cytoplasm and prominent nucleoli, divided by fibrous septa containing lymphocytes. Embryonal carcinoma and yolk sac tumor show more pleomorphic or glandular patterns, and Leydig cell tumors are sex cord-stromal tumors.