ABOP Diplomate cheat sheet
ABOP Diplomate · Keep the key ideas within reach.
Oral and Maxillofacial Surgical Pathology
Ameloblastoma: peripheral variant arises in gingiva without bone involvement; conventional variant is intraosseous and locally aggressive.
Odontogenic keratocyst: parakeratinized 6-8 cell epithelium, palisaded hyperchromatic basal layer, corrugated surface; PTCH1 mutation in syndromic cases.
Radicular cyst is the most common odontogenic cyst; lined by non-keratinized stratified squamous epithelium with inflammation and cholesterol clefts.
Osteosarcoma of jaws: sunburst periosteal reaction, malignant osteoid; pagetoid variant in older patients, gnathic variant in younger.
Squamous cell carcinoma of oral cavity: depth of invasion >5 mm and extranodal extension upstaged in AJCC 8th edition.
Verrucous carcinoma: broad pushing rete ridges, minimal atypia, no true invasion; distinguished from conventional SCC.
Pleomorphic adenoma of minor salivary gland in palate: must be excised with margin due to recurrence and malignant transformation risk.
Langerhans cell histiocytosis: eosinophilic granulocytes with grooved nuclei (coffee-bean); CD1a and Langerin positive.
Oral and Maxillofacial Medicine and Mucosal Disease
Recurrent aphthous stomatitis: minor (<1 cm, heals <2 weeks), major (>1 cm, scarring), herpetiform (clustered 1-3 mm).
Oral lichen planus: bilateral white striae (Wickham), T-cell mediated; malignant transformation risk ~1% per year.
Pemphigus vulgaris: intraepithelial split, suprabasal acantholysis, IgG against desmoglein 1 and 3; positive Nikolsky sign.
Mucous membrane pemphigoid: subepithelial split, linear IgG/C3 at basement membrane; ocular involvement mandates systemic therapy.
Oral candidiasis: pseudomembranous, erythematous, hyperplastic; PAS or silver stain shows pseudohyphae and spores.
Erythema multiforme: target lesions, acantholytic keratinocytes; HSV is the most common trigger.
Burning mouth syndrome: chronic oral pain without visible lesion; often associated with xerostomia, dysgeusia, and psychological factors.
Oral hairy leukoplakia: corrugated lateral tongue, EBV-driven, seen in HIV; in situ hybridization confirms EBV.
Odontogenic Cysts and Tumors
WHO classification: ameloblastoma, adenomatoid odontogenic tumor, calcifying epithelial odontogenic tumor (Pindborg), odontoma, cementoblastoma are benign; ameloblastic carcinoma and primary intraosseous carcinoma are malignant.
Odontoma is the most common odontogenic tumor; compound (tooth-like denticles) and complex (irregular mass).
Adenomatoid odontogenic tumor: 'two-thirds' rule - two-thirds in anterior maxilla, two-thirds in females, two-thirds associated with impacted canine.
Calcifying epithelial odontogenic tumor: Liesegang rings, amyloid deposits, polyhedral epithelial cells; mandibular premolar-molar region.
Odontogenic myxoma: soap-bubble or tennis-racket radiolucency; gelatinous, hypocellular with myxoid stroma.
Keratocystic odontogenic tumor (KCOT): high recurrence (up to 25-60%), associated with nevoid basal cell carcinoma syndrome.
Cementoblastoma: attached to tooth root, radiolucent halo, pain; must be differentiated from osteoblastoma.
Ameloblastic fibroma: biphasic - odontogenic epithelium in primitive fibrous stroma; more common in first two decades.
Salivary Gland Pathology
Pleomorphic adenoma: most common salivary tumor; PLAG1 or HMGA2 rearrangement; chondromyxoid stroma.
Warthin tumor: parotid tail, oncocytic epithelium, lymphoid stroma with germinal centers; associated with smoking.
Mucoepidermoid carcinoma: MAML2-CRTC1 fusion; mucinous, intermediate, and epidermoid cells; low vs high grade by architecture and atypia.
Adenoid cystic carcinoma: cribriform 'Swiss cheese' pattern, perineural invasion; MYB-NFIB fusion; late distant metastasis.
Acinic cell carcinoma: serous acinar differentiation, zymogen granules, PAS-positive, DOG1 positive; good prognosis.
Salivary duct carcinoma: high-grade, AR-positive, HER2-amplified subset; 'Roman bridge' comedonecrosis.
Secretory carcinoma: ETV6-NTRK3 fusion; S100 and mammaglobin positive; formerly mammary analogue secretory carcinoma.
Minor salivary gland tumors: palate most common site; malignant more common than benign in minor glands.
Bone and Fibro-osseous Lesions of the Jaws
Fibrous dysplasia: 'ground-glass' radiopacity, GNAS mutation; bone trabeculae lack osteoblastic rimming ('Chinese character').
Ossifying fibroma: well-circumscribed, bone and cementum-like spherules with osteoblastic rimming; mandible more common.
Cemento-osseous dysplasia: periapical, focal, or florid; African-American females; avoid biopsy in florid type due to infection risk.
Cherubism: bilateral multilocular radiolucencies in children; SH3BP2 mutation; self-limiting.
Paget disease of bone: mosaic pattern, elevated ALP, 'cotton wool' skull; risk of osteosarcoma transformation.
Central giant cell granuloma: multinucleated giant cells in vascular stroma; may respond to intralesional corticosteroids or calcitonin.
Brown tumor of hyperparathyroidism: elevated PTH and calcium; indistinguishable histologically from central giant cell granuloma.
Osteomyelitis: sequestrum, involucrum, inflammatory marrow; mandible more common; Actinomyces often isolated.
Head and Neck Soft Tissue Pathology
Nodular fasciitis: rapid growth, tissue-culture-like spindle cells, extravasated RBCs; benign, self-limiting.
Schwannoma: Antoni A (Verocay bodies) and Antoni B areas; S100 positive; encapsulated.
Neurofibroma: S100 positive, loose myxoid stroma; multiple lesions suggest NF1.
Myofibroma: biphasic, myoid nodules with hemangiopericytomatous vessels; common in infants and children.
Lipoma vs liposarcoma: atypical stromal cells, lipoblasts, MDM2 amplification favor liposarcoma.
Desmoid fibromatosis: infiltrative, beta-catenin nuclear positivity; high local recurrence, no metastasis.
Kaposi sarcoma: HHV-8 positive, slit-like vascular spaces, spindle cells; oral lesions in HIV/AIDS.
Epithelioid hemangioma: well-formed vessels with epithelioid endothelial cells and eosinophils; FOS rearrangement.
Hematolymphoid and Dermatologic Pathology of the Head and Neck
Diffuse large B-cell lymphoma: most common oral non-Hodgkin lymphoma; CD20 positive; extranodal site often Waldeyer ring.
Burkitt lymphoma: 'starry sky' pattern, MYC translocation t(8;14); endemic (jaw) and sporadic forms.
MALT lymphoma: extranodal marginal zone; associated with chronic inflammation and autoimmune disease.
Plasmacytoma: monoclonal plasma cells, CD138 positive, kappa or lambda restriction; rule out multiple myeloma.
Basal cell carcinoma: palisading peripheral cells, clefting, peritumoral mucin; most common skin malignancy of head and neck.
Squamous cell carcinoma of skin: keratin pearls, intercellular bridges; perineural invasion worsens prognosis.
Melanoma: S100, HMB-45, Melan-A positive; Breslow thickness and ulceration are key prognostic factors.
Merkel cell carcinoma: CK20 dot-like positivity, neuroendocrine markers; Merkel cell polyomavirus association.
Microscopic and Immunohistochemical Diagnosis
Cytokeratin (AE1/AE3, CK5/6): epithelial differentiation; p63/p40 for squamous differentiation.
S100 and SOX10: neural crest, melanoma, schwannoma; SOX10 more sensitive in spindle lesions.
Desmin and myogenin: skeletal muscle differentiation; myogenin and MyoD1 are specific.
CD31 and CD34: vascular endothelium; ERG is a sensitive nuclear vascular marker.
DOG1: acinic cell carcinoma and salivary acinar differentiation; also gastrointestinal stromal tumor.
p16 overexpression: HPV-associated oropharyngeal squamous cell carcinoma; combined with HPV ISH or PCR for confirmation.
Ki-67 proliferation index: useful in grading and prognosis across many tumors.
In situ hybridization: EBER for EBV, HPV for oropharyngeal carcinoma; high sensitivity and specificity.
Laboratory Management, Quality Assurance, and Regulatory Compliance
CLIA: laboratory categories (waived, moderate, high complexity); director qualifications vary by complexity.
CAP accreditation: requires proficiency testing, quality control, and documented competency assessment.
OSHA bloodborne pathogens standard: exposure control plan, HBV vaccination, PPE, and post-exposure evaluation.
HIPAA: protected health information safeguards; minimum necessary standard for disclosures.
Specimen labeling: two patient identifiers; time-out before procedure; chain of custody for forensic specimens.
Turnaround time monitoring: track from accession to report; outliers reviewed monthly.
Formalin fixation: 10% neutral buffered formalin; 10:1 fixative-to-tissue ratio; 6-48 hours for routine processing.
Critical value reporting: immediate notification documented with read-back verification.
Research Methodology, Biostatistics, and Evidence-Based Practice
Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); PPV and NPV depend on prevalence.
Odds ratio: case-control studies; relative risk: cohort studies; attributable risk from incidence difference.
Randomized controlled trial: randomization minimizes confounding; intention-to-treat preserves randomization benefits.
p-value: probability of observed or more extreme result under null; not the probability the null is true.
Confidence interval: 95% CI excludes 1 for OR/RR or 0 for mean difference indicates statistical significance at alpha 0.05.
Number needed to treat = 1/absolute risk reduction.
Levels of evidence: systematic reviews > RCTs > cohort > case-control > case series > expert opinion.
Bias types: selection, information, recall, publication; blinding and concealment reduce bias.
Oral and Maxillofacial Surgical Pathology
Ameloblastoma: peripheral variant arises in gingiva without bone involvement; conventional variant is intraosseous and locally aggressive.
Odontogenic keratocyst: parakeratinized 6-8 cell epithelium, palisaded hyperchromatic basal layer, corrugated surface; PTCH1 mutation in syndromic cases.
Radicular cyst is the most common odontogenic cyst; lined by non-keratinized stratified squamous epithelium with inflammation and cholesterol clefts.
Osteosarcoma of jaws: sunburst periosteal reaction, malignant osteoid; pagetoid variant in older patients, gnathic variant in younger.
Squamous cell carcinoma of oral cavity: depth of invasion >5 mm and extranodal extension upstaged in AJCC 8th edition.
Verrucous carcinoma: broad pushing rete ridges, minimal atypia, no true invasion; distinguished from conventional SCC.
Pleomorphic adenoma of minor salivary gland in palate: must be excised with margin due to recurrence and malignant transformation risk.
Langerhans cell histiocytosis: eosinophilic granulocytes with grooved nuclei (coffee-bean); CD1a and Langerin positive.
Oral and Maxillofacial Medicine and Mucosal Disease
Recurrent aphthous stomatitis: minor (<1 cm, heals <2 weeks), major (>1 cm, scarring), herpetiform (clustered 1-3 mm).
Oral lichen planus: bilateral white striae (Wickham), T-cell mediated; malignant transformation risk ~1% per year.
Pemphigus vulgaris: intraepithelial split, suprabasal acantholysis, IgG against desmoglein 1 and 3; positive Nikolsky sign.
Mucous membrane pemphigoid: subepithelial split, linear IgG/C3 at basement membrane; ocular involvement mandates systemic therapy.
Oral candidiasis: pseudomembranous, erythematous, hyperplastic; PAS or silver stain shows pseudohyphae and spores.
Erythema multiforme: target lesions, acantholytic keratinocytes; HSV is the most common trigger.
Burning mouth syndrome: chronic oral pain without visible lesion; often associated with xerostomia, dysgeusia, and psychological factors.
Oral hairy leukoplakia: corrugated lateral tongue, EBV-driven, seen in HIV; in situ hybridization confirms EBV.
Odontogenic Cysts and Tumors
WHO classification: ameloblastoma, adenomatoid odontogenic tumor, calcifying epithelial odontogenic tumor (Pindborg), odontoma, cementoblastoma are benign; ameloblastic carcinoma and primary intraosseous carcinoma are malignant.
Odontoma is the most common odontogenic tumor; compound (tooth-like denticles) and complex (irregular mass).
Adenomatoid odontogenic tumor: 'two-thirds' rule - two-thirds in anterior maxilla, two-thirds in females, two-thirds associated with impacted canine.
Calcifying epithelial odontogenic tumor: Liesegang rings, amyloid deposits, polyhedral epithelial cells; mandibular premolar-molar region.
Odontogenic myxoma: soap-bubble or tennis-racket radiolucency; gelatinous, hypocellular with myxoid stroma.
Keratocystic odontogenic tumor (KCOT): high recurrence (up to 25-60%), associated with nevoid basal cell carcinoma syndrome.
Cementoblastoma: attached to tooth root, radiolucent halo, pain; must be differentiated from osteoblastoma.
Ameloblastic fibroma: biphasic - odontogenic epithelium in primitive fibrous stroma; more common in first two decades.
Salivary Gland Pathology
Pleomorphic adenoma: most common salivary tumor; PLAG1 or HMGA2 rearrangement; chondromyxoid stroma.
Warthin tumor: parotid tail, oncocytic epithelium, lymphoid stroma with germinal centers; associated with smoking.
Mucoepidermoid carcinoma: MAML2-CRTC1 fusion; mucinous, intermediate, and epidermoid cells; low vs high grade by architecture and atypia.
Adenoid cystic carcinoma: cribriform 'Swiss cheese' pattern, perineural invasion; MYB-NFIB fusion; late distant metastasis.
Acinic cell carcinoma: serous acinar differentiation, zymogen granules, PAS-positive, DOG1 positive; good prognosis.
Salivary duct carcinoma: high-grade, AR-positive, HER2-amplified subset; 'Roman bridge' comedonecrosis.
Secretory carcinoma: ETV6-NTRK3 fusion; S100 and mammaglobin positive; formerly mammary analogue secretory carcinoma.
Minor salivary gland tumors: palate most common site; malignant more common than benign in minor glands.
Bone and Fibro-osseous Lesions of the Jaws
Fibrous dysplasia: 'ground-glass' radiopacity, GNAS mutation; bone trabeculae lack osteoblastic rimming ('Chinese character').
Ossifying fibroma: well-circumscribed, bone and cementum-like spherules with osteoblastic rimming; mandible more common.
Cemento-osseous dysplasia: periapical, focal, or florid; African-American females; avoid biopsy in florid type due to infection risk.
Cherubism: bilateral multilocular radiolucencies in children; SH3BP2 mutation; self-limiting.
Paget disease of bone: mosaic pattern, elevated ALP, 'cotton wool' skull; risk of osteosarcoma transformation.
Central giant cell granuloma: multinucleated giant cells in vascular stroma; may respond to intralesional corticosteroids or calcitonin.
Brown tumor of hyperparathyroidism: elevated PTH and calcium; indistinguishable histologically from central giant cell granuloma.
Osteomyelitis: sequestrum, involucrum, inflammatory marrow; mandible more common; Actinomyces often isolated.
Head and Neck Soft Tissue Pathology
Nodular fasciitis: rapid growth, tissue-culture-like spindle cells, extravasated RBCs; benign, self-limiting.
Schwannoma: Antoni A (Verocay bodies) and Antoni B areas; S100 positive; encapsulated.
Neurofibroma: S100 positive, loose myxoid stroma; multiple lesions suggest NF1.
Myofibroma: biphasic, myoid nodules with hemangiopericytomatous vessels; common in infants and children.
Lipoma vs liposarcoma: atypical stromal cells, lipoblasts, MDM2 amplification favor liposarcoma.
Desmoid fibromatosis: infiltrative, beta-catenin nuclear positivity; high local recurrence, no metastasis.
Kaposi sarcoma: HHV-8 positive, slit-like vascular spaces, spindle cells; oral lesions in HIV/AIDS.
Epithelioid hemangioma: well-formed vessels with epithelioid endothelial cells and eosinophils; FOS rearrangement.
Hematolymphoid and Dermatologic Pathology of the Head and Neck
Diffuse large B-cell lymphoma: most common oral non-Hodgkin lymphoma; CD20 positive; extranodal site often Waldeyer ring.
Burkitt lymphoma: 'starry sky' pattern, MYC translocation t(8;14); endemic (jaw) and sporadic forms.
MALT lymphoma: extranodal marginal zone; associated with chronic inflammation and autoimmune disease.
Plasmacytoma: monoclonal plasma cells, CD138 positive, kappa or lambda restriction; rule out multiple myeloma.
Basal cell carcinoma: palisading peripheral cells, clefting, peritumoral mucin; most common skin malignancy of head and neck.
Squamous cell carcinoma of skin: keratin pearls, intercellular bridges; perineural invasion worsens prognosis.
Melanoma: S100, HMB-45, Melan-A positive; Breslow thickness and ulceration are key prognostic factors.
Merkel cell carcinoma: CK20 dot-like positivity, neuroendocrine markers; Merkel cell polyomavirus association.
Microscopic and Immunohistochemical Diagnosis
Cytokeratin (AE1/AE3, CK5/6): epithelial differentiation; p63/p40 for squamous differentiation.
S100 and SOX10: neural crest, melanoma, schwannoma; SOX10 more sensitive in spindle lesions.
Desmin and myogenin: skeletal muscle differentiation; myogenin and MyoD1 are specific.
CD31 and CD34: vascular endothelium; ERG is a sensitive nuclear vascular marker.
DOG1: acinic cell carcinoma and salivary acinar differentiation; also gastrointestinal stromal tumor.
p16 overexpression: HPV-associated oropharyngeal squamous cell carcinoma; combined with HPV ISH or PCR for confirmation.
Ki-67 proliferation index: useful in grading and prognosis across many tumors.
In situ hybridization: EBER for EBV, HPV for oropharyngeal carcinoma; high sensitivity and specificity.
Laboratory Management, Quality Assurance, and Regulatory Compliance
CLIA: laboratory categories (waived, moderate, high complexity); director qualifications vary by complexity.
CAP accreditation: requires proficiency testing, quality control, and documented competency assessment.
OSHA bloodborne pathogens standard: exposure control plan, HBV vaccination, PPE, and post-exposure evaluation.
HIPAA: protected health information safeguards; minimum necessary standard for disclosures.
Specimen labeling: two patient identifiers; time-out before procedure; chain of custody for forensic specimens.
Turnaround time monitoring: track from accession to report; outliers reviewed monthly.
Formalin fixation: 10% neutral buffered formalin; 10:1 fixative-to-tissue ratio; 6-48 hours for routine processing.
Critical value reporting: immediate notification documented with read-back verification.
Research Methodology, Biostatistics, and Evidence-Based Practice
Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); PPV and NPV depend on prevalence.
Odds ratio: case-control studies; relative risk: cohort studies; attributable risk from incidence difference.
Randomized controlled trial: randomization minimizes confounding; intention-to-treat preserves randomization benefits.
p-value: probability of observed or more extreme result under null; not the probability the null is true.
Confidence interval: 95% CI excludes 1 for OR/RR or 0 for mean difference indicates statistical significance at alpha 0.05.
Number needed to treat = 1/absolute risk reduction.
Levels of evidence: systematic reviews > RCTs > cohort > case-control > case series > expert opinion.
Bias types: selection, information, recall, publication; blinding and concealment reduce bias.