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ABPS Dermatology (BCD) study materials
ABPS Dermatology (BCD) study resources

ABPS Dermatology (BCD) practice questions

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Question 1Medical Dermatology

Pinpoint bleeding that appears after a psoriatic scale is gently peeled away is called which sign?

  1. Darier sign
  2. Koebner phenomenon
  3. Auspitz sign Correct answer.
  4. Nikolsky sign

Explanation

In psoriasis the suprapapillary epidermis is thinned and overlies dilated, tortuous dermal capillaries, so removing the scale ruptures these vessels and produces pinpoint bleeding. This is the Auspitz sign. The other eponyms describe different mechanical behaviors of skin and are not related to capillary bleeding under a scale.

Question 2Medical Dermatology

A 62-year-old man has a slowly growing pearly papule with fine telangiectasias and a rolled border on the upper lip. Which diagnosis is most likely?

  1. Melanoma
  2. Actinic keratosis
  3. Squamous cell carcinoma
  4. Basal cell carcinoma Correct answer.

Explanation

A pearly, translucent papule with rolled edges, surface telangiectasias and a tendency to ulcerate is the classic description of nodular basal cell carcinoma on sun-exposed head and neck skin. It grows slowly and rarely metastasizes but is locally destructive.

Question 3Medical Dermatology

A scaly annular plaque with central clearing is scraped and examined with potassium hydroxide. Which finding confirms a dermatophyte infection?

  1. Round yeast cells with a wide capsule
  2. Spaghetti and meatball appearance
  3. Septate branching hyphae Correct answer.
  4. Budding yeasts with pseudohyphae

Explanation

Dermatophytes are filamentous fungi that appear on KOH as long, septate, branching hyphae crossing the scale. Yeast forms and pseudohyphae suggest Candida, whereas encapsulated round yeasts suggest Cryptococcus.

Question 4Medical Dermatology

A 20-year-old woman develops a single 3-cm oval scaly patch on her back, and two weeks later many smaller oval lesions appear along the lines of the ribs. Which diagnosis fits best?

  1. Secondary syphilis
  2. Tinea corporis
  3. Pityriasis rosea Correct answer.
  4. Guttate psoriasis

Explanation

A herald patch followed one to two weeks later by a widespread eruption of oval lesions oriented along the ribs, creating a Christmas-tree pattern on the back, is typical of pityriasis rosea. The eruption usually resolves spontaneously within weeks.

Question 5Medical Dermatology

Which feature most supports ordinary urticaria rather than urticarial vasculitis?

  1. Individual wheals resolve within 24 hours Correct answer.
  2. Biopsy shows leukocytoclasia
  3. Each lesion lasts three to five days
  4. Lesions leave residual purpura

Explanation

Ordinary urticarial wheals are transient, usually clearing within 24 hours without leaving a mark. Urticarial vasculitis lesions persist longer than a day, often leave purpura or pigmentation, and show leukocytoclastic vasculitis on biopsy.

Question 6Medical Dermatology

Which organism is most closely linked to the pathogenesis of seborrheic dermatitis?

  1. Corynebacterium minutissimum
  2. Cutibacterium acnes
  3. Staphylococcus aureus
  4. Malassezia species Correct answer.

Explanation

Seborrheic dermatitis is an inflammatory response to Malassezia yeasts that colonize sebaceous areas such as the scalp, eyebrows and nasolabial folds, which is why antifungal therapy is effective. The other listed organisms cause acne, impetiginization and erythrasma respectively.

Question 7Medical Dermatology

A 30-year-old has sharply demarcated, completely depigmented macules on both hands and around the mouth. Which diagnosis is most likely?

  1. Nevus depigmentosus
  2. Vitiligo Correct answer.
  3. Postinflammatory hypopigmentation
  4. Pityriasis versicolor

Explanation

Acquired, sharply demarcated, complete loss of pigment in a periorificial and acral distribution is characteristic of vitiligo, an autoimmune destruction of melanocytes. Wood lamp examination shows bright blue-white accentuation of depigmented areas.

Question 8Medical Dermatology

Which organism is the most common cause of nonpurulent cellulitis in adults?

  1. Pasteurella multocida
  2. Vibrio vulnificus
  3. Escherichia coli
  4. Streptococcus pyogenes Correct answer.

Explanation

Nonpurulent cellulitis is most often caused by beta-hemolytic streptococci, particularly Streptococcus pyogenes, with Staphylococcus aureus also contributing. Purulent collections or abscesses shift the likelihood toward S. aureus.

Question 9Medical Dermatology

A 4-year-old with chronic itching has lichenified plaques in the antecubital and popliteal fossae. What is the most appropriate first-line topical treatment?

  1. Medium-potency topical corticosteroid Correct answer.
  2. Topical calcineurin inhibitor twice daily
  3. Topical antibiotic
  4. Coal tar preparation

Explanation

Atopic dermatitis is treated first with topical corticosteroids, with potency chosen according to body site and severity; a medium-potency agent is appropriate for limb flexures in a child. Emollients and trigger avoidance are used alongside.

Question 10Medical Dermatology

Which feature of a primary cutaneous melanoma determines the T stage and is the strongest predictor of survival?

  1. Clark level of invasion
  2. Lesion diameter
  3. Breslow thickness Correct answer.
  4. Degree of surrounding solar elastosis

Explanation

Breslow thickness, measured in millimeters from the granular layer to the deepest tumor cell, is the single most important prognostic factor and drives T staging in melanoma. Clark level is reported but no longer used for staging.

Question 11Medical Dermatology

Allergic contact dermatitis to nickel is mediated by which mechanism?

  1. Direct complement activation by the metal
  2. Immune complex deposition in vessel walls
  3. IgE-mediated immediate hypersensitivity
  4. Type IV cell-mediated hypersensitivity Correct answer.

Explanation

Nickel allergy is a delayed-type hypersensitivity reaction in which sensitized T lymphocytes are activated by the hapten, producing eczema 24 to 72 hours after contact. Patch testing reproduces this response.

Question 12Medical Dermatology

A patient has flaccid bullae and painful oral erosions, and biopsy shows intraepidermal separation above the basal layer. Which antibody is most characteristic?

  1. Anti-desmoglein 1 only
  2. Anti-BP180
  3. Anti-type VII collagen
  4. Anti-desmoglein 3 Correct answer.

Explanation

Pemphigus vulgaris is caused by IgG autoantibodies against desmoglein 3, which is concentrated in mucosal epithelium and the deep epidermis; this produces suprabasal acantholysis, flaccid blisters and prominent oral involvement. Anti-desmoglein 1 alone tends to produce superficial, mucosa-sparing disease.

Question 13Medical Dermatology

Direct immunofluorescence of perilesional skin in bullous pemphigoid typically shows which pattern?

  1. Fibrinogen within vessel walls
  2. Granular IgG along the dermoepidermal junction
  3. Linear IgG and C3 at the basement membrane Correct answer.
  4. IgA in dermal papillae

Explanation

Bullous pemphigoid is a subepidermal blistering disease directed against hemidesmosomal antigens BP180 and BP230, producing continuous linear deposits of IgG and C3 along the basement membrane zone.

Question 14Medical Dermatology

Which direct immunofluorescence finding is characteristic of dermatitis herpetiformis?

  1. C3 in the superficial dermis
  2. IgA in dermal papillae Correct answer.
  3. IgM within vessel walls
  4. Linear IgG at the basement membrane

Explanation

Dermatitis herpetiformis shows granular IgA deposits concentrated in the dermal papillae of perilesional skin, corresponding to the microabscesses at the tips of papillae seen on histology. The deposits reflect the gluten-sensitive enteropathy that underlies the disease.

Question 15Medical Dermatology

A young adult develops symmetric targetoid lesions on the hands and forearms with no mucosal involvement, two weeks after a cold sore. Which trigger is most likely?

  1. Mycoplasma pneumoniae
  2. Herpes simplex virus Correct answer.
  3. Sulfa antibiotics
  4. Epstein-Barr virus

Explanation

Erythema multiforme is most often triggered by herpes simplex virus infection, producing acrally distributed target lesions with little or no mucosal disease. Mycoplasma and drugs are recognized but less common precipitants of this pattern.

Question 16Medical Dermatology

A 19-year-old with nodulocystic acne is started on isotretinoin. Which laboratory monitoring is required?

  1. Monthly serum creatinine and urinalysis
  2. Weekly complete blood count with differential
  3. Baseline electrocardiogram and echocardiogram
  4. Fasting lipids and liver enzymes Correct answer.

Explanation

Isotretinoin can raise triglycerides, cholesterol and transaminases, so fasting lipids and liver enzymes are checked at baseline and again after about four to eight weeks of therapy. Pregnancy testing is also mandatory because the drug is highly teratogenic.

Question 17Medical Dermatology

A fair-skinned 45-year-old woman has flushing, telangiectasias and papulopustules on the cheeks. Which trigger is most commonly reported?

  1. Topical retinoid use
  2. High-fiber diet
  3. Cold humid air
  4. Sun exposure and heat Correct answer.

Explanation

Rosacea is aggravated by factors that cause vasodilation, and ultraviolet exposure, heat, spicy foods and alcohol are the most frequently reported triggers. Sun protection is therefore a central part of management.

Question 18Medical Dermatology

Which finding at the edge of a circumscribed bald patch supports alopecia areata?

  1. Follicular plugging with yellow dots
  2. Exclamation mark hairs Correct answer.
  3. Comma-shaped hairs
  4. Corkscrew hairs

Explanation

Short, broken hairs that are narrower at the base than at the tip, called exclamation mark hairs, are seen at the active periphery of alopecia areata patches. They reflect inflammation of the hair bulb during active disease.

Question 19Medical Dermatology

A patient has violaceous, flat-topped, intensely pruritic papules with a lacy white network on the surface. What is this network called?

  1. Koebner lines
  2. Auspitz striae
  3. Wickham striae Correct answer.
  4. Darier lines

Explanation

Wickham striae are the fine, white, reticulated lines seen on the surface of lichen planus papules and are best visualized with a hand lens or dermoscopy. They correspond to hypergranulosis and compact hyperkeratosis.

Question 20Medical Dermatology

A patient has intense nocturnal itching and linear burrows in the finger webs. Which treatment is first-line for the patient and close contacts?

  1. Oral acyclovir
  2. Oral fluconazole
  3. Topical mupirocin
  4. Topical permethrin 5% Correct answer.

Explanation

Scabies is treated with a topical scabicide such as permethrin 5% applied from the neck down and washed off after 8 to 14 hours, with a repeat application in one week. All close contacts must be treated simultaneously regardless of symptoms.

Question 21Medical Dermatology

A patient started lamotrigine three weeks ago and now has fever, painful skin and epidermal detachment involving 18% of body surface area with erosions at two mucosal sites. Which classification is correct?

  1. Toxic epidermal necrolysis
  2. Stevens-Johnson syndrome/toxic epidermal necrolysis overlap Correct answer.
  3. Erythema multiforme major
  4. Stevens-Johnson syndrome

Explanation

Drug-induced epidermal necrolysis is classified by the percentage of detached body surface area: under 10% is Stevens-Johnson syndrome, over 30% is toxic epidermal necrolysis, and 10 to 30% is overlap. This patient's 18% detachment with mucosal involvement places the reaction in the overlap category.

Question 22Medical Dermatology

A biopsy of a persistent scaly patch shows atypical epidermotropic CD4+ T cells and collections of lymphocytes within the epidermis. What are these intraepidermal collections called?

  1. Munro microabscesses
  2. Grenz zone collections
  3. Kogoj spongiform pustules
  4. Pautrier microabscesses Correct answer.

Explanation

Pautrier microabscesses are intraepidermal clusters of atypical lymphocytes and are a histologic hallmark of mycosis fungoides, the most common cutaneous T-cell lymphoma. Epidermotropism with little spongiosis is another key feature.

Question 23Medical Dermatology

A 40-year-old with bloody diarrhea develops a painful, rapidly enlarging ulcer with a violaceous, undermined border after a minor scrape. Which diagnosis is most likely?

  1. Pyoderma gangrenosum Correct answer.
  2. Squamous cell carcinoma
  3. Venous stasis ulcer
  4. Ecthyma gangrenosum

Explanation

Pyoderma gangrenosum begins as a tender pustule or nodule that breaks down into an ulcer with a violaceous, undermined edge, and it shows pathergy after minor trauma. It is strongly associated with inflammatory bowel disease, which explains the bloody diarrhea here.

Question 24Medical Dermatology

A 52-year-old woman with proximal muscle weakness has symmetric violaceous papules over the knuckles. What are these lesions called?

  1. Osler nodes
  2. Gottron papules Correct answer.
  3. Shagreen patches
  4. Heliotrope rash

Explanation

Gottron papules are violaceous, slightly scaly papules over the metacarpophalangeal and interphalangeal joints in dermatomyositis and are considered highly specific for the disease. They differ from the heliotrope rash, which is a violaceous periorbital eruption.

Question 25Medical Dermatology

A patient with acute myeloid leukemia develops fever, neutrophilia and tender, bright red edematous plaques on the arms. Biopsy shows a dense neutrophilic dermal infiltrate without vasculitis. Which diagnosis is most likely?

  1. Cellulitis
  2. Sweet syndrome Correct answer.
  3. Erythema nodosum
  4. Leukocytoclastic vasculitis

Explanation

Sweet syndrome, or acute febrile neutrophilic dermatosis, presents with fever, peripheral neutrophilia and tender erythematous plaques, and about one fifth of cases are associated with hematologic malignancy, especially acute myeloid leukemia. Histology shows a dense neutrophilic infiltrate without true vasculitis.

Question 26Medical Dermatology

A biopsy from a well-demarcated erythematous plaque with silvery scale shows collections of neutrophils within the stratum corneum. What are these collections called?

  1. Kogoj spongiform pustules
  2. Wickham striae
  3. Munro microabscesses Correct answer.
  4. Pautrier microabscesses

Explanation

Neutrophil collections in the stratum corneum of a psoriatic plaque are Munro microabscesses. Similar neutrophil collections within the spinous layer are termed Kogoj spongiform pustules.

Question 27Medical Dermatology

A 6-year-old has erosions with honey-colored crusting around the nose and mouth. Which organism is most commonly responsible for this form of impetigo?

  1. Pseudomonas aeruginosa
  2. Staphylococcus aureus Correct answer.
  3. Mycobacterium marinum
  4. Corynebacterium diphtheriae

Explanation

Nonbullous impetigo is most often caused by Staphylococcus aureus, with Streptococcus pyogenes also contributing in some cases. The honey-colored crust reflects dried serum at the site of superficial epidermal infection.

Question 28Medical Dermatology

A young adult has hypopigmented, finely scaly macules on the chest, and KOH microscopy shows short hyphae mixed with round spores. Which description matches this finding?

  1. Bird's-beak branching septate hyphae
  2. Spaghetti and meatballs appearance Correct answer.
  3. Cigar bodies within multinucleated giant cells
  4. Rocket-shaped arthroconidia in hair shafts

Explanation

The KOH finding of short hyphae and spores is commonly described as spaghetti and meatballs and supports tinea versicolor. The organism is Malassezia, which is part of normal skin flora.

Question 29Medical Dermatology

A firm brown papule on the leg is pinched between the thumb and forefinger, producing a central depression. What is this finding called?

  1. Auspitz sign
  2. Darier sign
  3. Dimple sign Correct answer.
  4. Nikolsky sign

Explanation

The dimple sign is produced by lateral compression of a dermatofibroma and reflects tethering of the lesion to the dermis. It helps distinguish a dermatofibroma from other firm papules.

Question 30Medical Dermatology

A 22-year-old develops a single oval salmon-colored patch with a collarette of scale on the back, followed by smaller similar lesions in a Christmas-tree distribution. Which virus is most strongly associated with this eruption?

  1. Human papillomavirus 16
  2. Human herpesvirus 8
  3. Parvovirus B19
  4. Human herpesvirus 7 Correct answer.

Explanation

Pityriasis rosea is associated with reactivation of human herpesvirus 6 and 7. It classically begins with a herald patch and then produces smaller oval lesions along cleavage lines on the trunk.

Question 31Medical Dermatology

A 7-year-old has scaling of the scalp with broken hairs, and culture grows Microsporum canis. Which oral agent is first-line therapy for this infection?

  1. Ketoconazole
  2. Griseofulvin Correct answer.
  3. Terbinafine
  4. Fluconazole

Explanation

Griseofulvin remains first-line for tinea capitis caused by Microsporum species, which respond less well to terbinafine. Topical therapy alone does not penetrate the hair follicle adequately, so an oral agent is required.

Question 32Medical Dermatology

A 65-year-old has painful grouped vesicles confined to a thoracic dermatome that appeared two days ago. Antiviral therapy for herpes zoster is most effective when started within which window?

  1. 14 days after rash onset
  2. 72 hours after rash onset Correct answer.
  3. 7 days after rash onset
  4. Beginning 24 hours before the rash appears

Explanation

Antiviral therapy for herpes zoster should ideally begin within 72 hours of rash onset to reduce duration and severity and to lower the risk of postherpetic neuralgia. Starting earlier in the course is better, and treatment may still be considered in some patients after 72 hours.

Question 33Medical Dermatology

A 60-year-old fair-skinned man has a pearly papule with a rolled edge and fine telangiectasias on the nose. Which diagnosis is most likely?

  1. Nodular melanoma
  2. Basal cell carcinoma Correct answer.
  3. Sebaceous hyperplasia
  4. Squamous cell carcinoma

Explanation

A pearly papule with rolled borders and telangiectasias on sun-exposed skin is the classic description of basal cell carcinoma. It is the most common cutaneous malignancy and rarely metastasizes but can cause local destruction.

Question 34Medical Dermatology

A 30-year-old has recurrent pruritic wheals for eight weeks with no identifiable trigger. What is the first-line treatment for chronic spontaneous urticaria?

  1. Cetirizine Correct answer.
  2. Omalizumab
  3. Prednisone
  4. Cyclosporine

Explanation

Second-generation H1 antihistamines such as cetirizine are first-line for chronic spontaneous urticaria because they control symptoms with fewer sedating effects. Doses may be increased before adding other agents.

Question 35Medical Dermatology

A woman develops a round, dusky violaceous plaque on the lip each time she takes ibuprofen; the lesion heals with residual hyperpigmentation. What is the most likely diagnosis?

  1. Fixed drug eruption Correct answer.
  2. Stevens-Johnson syndrome
  3. Erythema multiforme
  4. Lichen planus

Explanation

A fixed drug eruption recurs at the same site with each exposure to the culprit drug and leaves postinflammatory hyperpigmentation. The lips and genitalia are common locations.

Question 36Medical Dermatology

A 35-year-old woman has tender, erythematous nodules on both shins and arthralgias. What is the most likely diagnosis?

  1. Cellulitis
  2. Erythema induratum
  3. Erythema nodosum Correct answer.
  4. Polyarteritis nodosa

Explanation

Erythema nodosum causes tender, erythematous nodules on the anterior shins and reflects septal panniculitis. It may be triggered by streptococcal infection, sarcoidosis, inflammatory bowel disease, or medications.

Question 37Medical Dermatology

A 50-year-old man with alcohol use and hepatitis C has fragile blisters and erosions on the dorsal hands, increased facial hair, and dark urine. Which enzyme is deficient in this condition?

  1. Uroporphyrinogen decarboxylase Correct answer.
  2. Ferrochelatase
  3. Protoporphyrinogen oxidase
  4. Delta-aminolevulinic acid dehydratase

Explanation

Porphyria cutanea tarda results from deficiency of uroporphyrinogen decarboxylase and presents with photosensitive fragility, blisters on sun-exposed dorsal hands, hypertrichosis, and dark urine. Alcohol, hepatitis C, and iron overload are common triggers.

Question 38Medical Dermatology

A 55-year-old has a dark longitudinal band on the thumbnail that extends onto the proximal nail fold. What is the name of this sign?

  1. Koebner phenomenon
  2. Hutchinson sign Correct answer.
  3. Crowe sign
  4. Auspitz sign

Explanation

Extension of nail apparatus pigment onto the proximal nail fold is Hutchinson sign, which raises concern for subungual melanoma. It indicates pigment in the surrounding skin and warrants urgent biopsy.

Question 39Medical Dermatology

A 45-year-old woman has Raynaud phenomenon, sclerodactyly, esophageal dysmotility, and facial telangiectasias; testing shows anticentromere antibodies. Which diagnosis is most likely?

  1. Limited cutaneous scleroderma Correct answer.
  2. Dermatomyositis
  3. Diffuse cutaneous scleroderma
  4. Mixed connective tissue disease

Explanation

Anticentromere antibodies are strongly associated with limited cutaneous systemic sclerosis, formerly called CREST syndrome. The features include calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasias.

Question 40Medical Dermatology

An 80-year-old has a rapidly growing, painless red-purple nodule on the sun-exposed cheek; biopsy shows small blue cells with neuroendocrine features. Which virus is most strongly associated?

  1. Human herpesvirus 8
  2. Merkel cell polyoma Correct answer.
  3. Human papillomavirus type 18
  4. Epstein-Barr virus

Explanation

Merkel cell carcinoma is an aggressive neuroendocrine skin cancer associated with Merkel cell polyomavirus in many cases. Sun exposure and advanced age are also important risk factors.

Question 41Dermatopathology

In a normal skin biopsy, where are melanocytes normally located?

  1. Within the stratum corneum
  2. Basal epidermal layer Correct answer.
  3. In the papillary dermis
  4. In the reticular dermis

Explanation

Melanocytes are dendritic cells that reside along the basal layer of the epidermis, where they transfer melanin to neighboring keratinocytes. They are not normally found in the stratum corneum or as resident cells of the dermis.

Question 42Dermatopathology

Which histologic feature is most characteristic of psoriasis vulgaris?

  1. Palisading granulomas around degenerated collagen
  2. Subcorneal acantholysis with a row of tombstone basal cells
  3. Bandlike lymphocytic infiltrate obscuring the dermoepidermal junction
  4. Neutrophils within parakeratosis in the stratum corneum Correct answer.

Explanation

Psoriasis shows regular acanthosis, hypogranulosis, and confluent parakeratosis, often with collections of neutrophils in the stratum corneum called Munro microabscesses. These findings reflect the accelerated epidermal turnover and neutrophilic inflammation of the disease.

Question 43Dermatopathology

Which special stain directly demonstrates melanin pigment?

  1. Periodic acid-Schiff
  2. Prussian blue
  3. Congo red
  4. Fontana-Masson Correct answer.

Explanation

Fontana-Masson is a silver reduction method that stains melanin black, making it useful for confirming melanocytic differentiation or pigment deposition. Other stains highlight different substances and do not directly demonstrate melanin.

Question 44Dermatopathology

Direct immunofluorescence of perilesional skin in pemphigus vulgaris typically shows which pattern?

  1. Intercellular IgG throughout the epidermis Correct answer.
  2. Fibrinogen deposition in vessel walls
  3. Granular IgA in dermal papillae
  4. Linear IgG and C3 along the basement membrane zone

Explanation

Pemphigus vulgaris is caused by antibodies against desmosomal proteins, producing intercellular IgG deposition in a netlike epidermal pattern. This contrasts with bullous pemphigoid, which shows linear deposition along the basement membrane zone.

Question 45Dermatopathology

Which marker is most characteristic of Langerhans cells?

  1. CD1a Correct answer.
  2. CD138
  3. CD34
  4. CD68

Explanation

Langerhans cells are dendritic antigen-presenting cells that express CD1a and langerin, and they contain Birbeck granules on electron microscopy. CD1a is widely used to identify Langerhans cell proliferations.

Question 46Dermatopathology

A sharply demarcated pigmented plaque on the back of an older adult shows epidermal hyperplasia with horn pseudocysts. What is the most likely diagnosis?

  1. Melanoma in situ
  2. Seborrheic keratosis Correct answer.
  3. Pigmented basal cell carcinoma
  4. Actinic keratosis

Explanation

Seborrheic keratosis is a benign epidermal proliferation characterized by basaloid cells, horn pseudocysts, and a stuck-on appearance. The presence of horn pseudocysts is a helpful clue that distinguishes it from melanoma and basal cell carcinoma.

Question 47Dermatopathology

Which feature is typical of nodular basal cell carcinoma?

  1. Subepidermal blister with eosinophils
  2. Peripheral palisading with clefts Correct answer.
  3. Epidermotropism of atypical lymphocytes
  4. Keratin pearls and intercellular bridges

Explanation

Nodular basal cell carcinoma forms dermal nests of basaloid cells with peripheral palisading and retraction clefts between the tumor and surrounding stroma. These features help distinguish it from squamous cell carcinoma and other tumors.

Question 48Dermatopathology

Which is the most common histologic subtype of cutaneous melanoma overall?

  1. Superficial spreading Correct answer.
  2. Nodular melanoma
  3. Acral lentiginous melanoma
  4. Lentigo maligna melanoma

Explanation

Superficial spreading melanoma is the most common subtype overall and typically shows a radial growth phase with atypical melanocytes spread along the epidermis. Nodular, lentigo maligna, and acral lentiginous melanomas are less common overall.

Question 49Dermatopathology

A biopsy of an oral erosion shows suprabasal acantholysis with basal keratinocytes attached to the basement membrane, forming a tombstone row. Which diagnosis is most likely?

  1. Dermatitis herpetiformis
  2. Pemphigus vulgaris Correct answer.
  3. Lichen planus
  4. Bullous pemphigoid

Explanation

Pemphigus vulgaris causes suprabasal acantholysis because antibodies disrupt desmoglein-mediated adhesion, leaving a single row of basal keratinocytes attached to the basement membrane. This produces the classic tombstone appearance.

Question 50Dermatopathology

A pruritic purple papule shows hyperkeratosis, wedge-shaped hypergranulosis, saw-tooth rete ridges, and a bandlike lymphocytic infiltrate with Civatte bodies. What is the diagnosis?

  1. Lichen planus Correct answer.
  2. Tinea corporis
  3. Psoriasis
  4. Lupus erythematosus

Explanation

Lichen planus classically shows hyperkeratosis, wedge-shaped hypergranulosis, saw-tooth rete ridges, and a bandlike lymphocytic infiltrate at the dermoepidermal junction. Civatte bodies are apoptotic keratinocytes commonly seen in this interface dermatitis.