I85PREP
⌘ K
ABD Dermatopathology study materials
ABD Dermatopathology study resources

ABD Dermatopathology practice questions

One question at a time. Build your ABD Dermatopathology understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Which histologic feature is most characteristic of lichen planus?

  1. Spongiform pustules of Kogoj
  2. Subepidermal clefting
  3. Perivascular nuclear dust
  4. Wedge-shaped hypergranulosis Correct answer.

Explanation

Lichen planus produces a lichenoid interface dermatitis with a bandlike lymphocytic infiltrate, saw-tooth rete ridges, wedge-shaped hypergranulosis, and apoptotic keratinocytes (Civatte bodies). These changes reflect basal keratinocyte injury and chronic inflammation at the dermoepidermal junction.

Question 2Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

The defining epidermal change of acute spongiotic dermatitis is:

  1. Confluent parakeratosis
  2. Acantholysis
  3. Vacuolar interface change
  4. Intercellular edema Correct answer.

Explanation

Spongiosis is intercellular edema between keratinocytes that stretches desmosomes and can form intraepidermal vesicles in acute eczema. It is the hallmark of spongiotic dermatitis and appears as widened pale spaces between keratinocytes.

Question 3Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy of a well-developed psoriatic plaque most likely shows:

  1. Munro microabscesses Correct answer.
  2. Flame figures
  3. Saw-tooth rete ridges
  4. Pautrier microabscesses

Explanation

Psoriasis shows parakeratosis containing neutrophils (Munro microabscesses), regular acanthosis, thinned suprapapillary plates, and dilated capillaries in dermal papillae. These findings reflect increased epidermal turnover and neutrophilic inflammation.

Question 4Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Direct immunofluorescence in bullous pemphigoid typically demonstrates:

  1. Intercellular IgG in the epidermis
  2. Linear IgG and C3 at the BMZ Correct answer.
  3. Granular IgA in dermal papillae
  4. Linear IgA along the basement membrane zone

Explanation

Bullous pemphigoid autoantibodies target BP180 and BP230 in hemidesmosomes, producing linear IgG and C3 along the basement membrane zone. The blister is subepidermal and often contains eosinophils.

Question 5Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Sarcoidal granulomas are best described as:

  1. Caseating granulomas with Langhans giant cells
  2. Palisading granulomas around necrobiotic collagen
  3. Naked noncaseating granulomas Correct answer.
  4. Suppurative granulomas with neutrophils

Explanation

Sarcoidosis forms tight, noncaseating granulomas with a sparse lymphocytic rim, often described as naked granulomas. Caseation suggests tuberculosis, palisading around necrobiosis suggests granuloma annulare, and suppuration suggests infection.

Question 6Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Leukocytoclastic vasculitis is characterized by:

  1. Fibrinoid necrosis with nuclear dust Correct answer.
  2. Intimal proliferation without inflammation
  3. Granulomatous arteritis
  4. Dense eosinophilic infiltrate

Explanation

Leukocytoclastic vasculitis affects small postcapillary venules and shows fibrinoid necrosis of vessel walls, neutrophilic infiltration, and leukocytoclasia (nuclear dust). These changes result from immune-complex deposition and complement activation.

Question 7Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Which finding favors lupus erythematosus over lichen planus?

  1. Bandlike infiltrate obscuring the junction
  2. Wedge-shaped hypergranulosis
  3. Saw-tooth rete ridges
  4. Increased dermal mucin Correct answer.

Explanation

Lupus erythematosus shows vacuolar interface change with perivascular and periadnexal lymphocytic infiltrates and increased dermal mucin. Lichen planus instead shows wedge-shaped hypergranulosis, saw-tooth rete ridges, and a dense bandlike junctional infiltrate.

Question 8Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A characteristic epidermal finding in pityriasis rosea is:

  1. Fibrinoid vessel necrosis
  2. Deep necrotizing granulomas
  3. Extravasated erythrocytes Correct answer.
  4. Subepidermal blister

Explanation

Pityriasis rosea shows spongiosis, focal parakeratosis, mild acanthosis, and extravasated erythrocytes within the epidermis. The erythrocyte extravasation is a useful clue that is not typical of ordinary eczema.

Question 9Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Which feature most favors a lichenoid drug eruption over idiopathic lichen planus?

  1. Wedge-shaped hypergranulosis
  2. Bandlike lymphocytic infiltrate at the junction
  3. Saw-tooth rete ridges
  4. Eosinophils and parakeratosis Correct answer.

Explanation

Lichenoid drug eruptions often show parakeratosis, eosinophils, a deeper perivascular infiltrate, and focal keratinocyte necrosis. Idiopathic lichen planus usually lacks parakeratosis and eosinophils and has wedge-shaped hypergranulosis and saw-tooth rete ridges.

Question 10Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

In a patient with photosensitivity and proximal muscle weakness, a skin biopsy showing interface dermatitis with dermal mucin most suggests:

  1. Dermatomyositis Correct answer.
  2. Pityriasis rosea
  3. Lichen planus
  4. Psoriasis

Explanation

Dermatomyositis produces vacuolar interface dermatitis with increased dermal mucin and often only mild inflammation, matching photosensitivity and proximal myopathy. Lichen planus lacks mucin, psoriasis is psoriasiform, and pityriasis rosea is spongiotic.

Question 11Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Allergic contact dermatitis is distinguished from irritant contact dermatitis by:

  1. Fibrinoid necrosis of vessels
  2. Marked parakeratosis with neutrophils
  3. Subepidermal clefting
  4. Eosinophils and Langerhans cells Correct answer.

Explanation

Allergic contact dermatitis is a type IV hypersensitivity reaction with spongiosis, eosinophils, and Langerhans cell microabscesses. Irritant contact dermatitis is caused by direct toxicity and shows keratinocyte necrosis with less prominent inflammation.

Question 12Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Pityriasis rubra pilaris characteristically shows:

  1. Saw-tooth rete ridges
  2. Munro microabscesses
  3. Checkerboard parakeratosis Correct answer.
  4. Subepidermal blister with eosinophils

Explanation

Pityriasis rubra pilaris shows alternating orthokeratosis and parakeratosis in a checkerboard pattern, follicular plugging, a thickened granular layer, and broad rete ridges. Munro microabscesses favor psoriasis, saw-tooth rete ridges favor lichen planus, and subepidermal blistering favors a bullous disease.

Question 13Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Lichen simplex chronicus is best characterized by:

  1. Regular acanthosis with thinned suprapapillary plates
  2. Irregular acanthosis with compact hyperkeratosis Correct answer.
  3. Subepidermal blister with eosinophils
  4. Vacuolar interface change with mucin

Explanation

Lichen simplex chronicus results from chronic rubbing and shows irregular acanthosis, hypergranulosis, compact orthokeratosis, and vertically oriented collagen bundles in the papillary dermis. It lacks the regular acanthosis and thinned suprapapillary plates of psoriasis.

Question 14Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Pemphigus vulgaris is characterized by:

  1. Granular IgA in papillae
  2. Subepidermal blister with eosinophils and neutrophils
  3. Suprabasal acantholysis with tombstoning Correct answer.
  4. Subepidermal blister with neutrophils

Explanation

Pemphigus vulgaris is caused by IgG against desmoglein 3, leading to suprabasal acantholysis and a row of basal keratinocytes attached to the basement membrane (tombstoning). Direct immunofluorescence shows intercellular IgG.

Question 15Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Dermatitis herpetiformis shows:

  1. Linear IgG along the basement membrane zone
  2. Neutrophilic microabscesses in dermal papillae Correct answer.
  3. Suprabasal acantholysis
  4. Palisading granulomas

Explanation

Dermatitis herpetiformis features granular IgA deposits in dermal papillae with neutrophilic microabscesses that coalesce into subepidermal blisters. It is associated with gluten-sensitive enteropathy.

Question 16Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Linear IgA bullous dermatosis is best identified by:

  1. Linear IgG and C3
  2. Intercellular IgG
  3. Granular IgA deposited in dermal papillae
  4. Linear IgA at the basement membrane Correct answer.

Explanation

Linear IgA bullous dermatosis shows linear IgA deposition along the basement membrane zone. Granular IgA in dermal papillae indicates dermatitis herpetiformis, intercellular IgG indicates pemphigus, and linear IgG with C3 indicates bullous pemphigoid.

Question 17Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Erythema multiforme typically shows:

  1. Naked granulomas
  2. Necrotic keratinocytes with sparse inflammation Correct answer.
  3. Dense neutrophilic infiltrate with fibrinoid necrosis
  4. Spongiform pustules

Explanation

Erythema multiforme produces interface dermatitis with scattered necrotic keratinocytes, vacuolar change, and relatively sparse inflammation. Severe cases may develop subepidermal blistering from extensive keratinocyte death.

Question 18Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Granuloma annulare is distinguished from necrobiosis lipoidica by:

  1. Caseating granulomas
  2. Mucin deposition and palisading histiocytes Correct answer.
  3. Neutrophilic microabscesses
  4. Layered granulomas with plasma cells

Explanation

Granuloma annulare shows palisading histiocytes around necrobiotic collagen with increased mucin. Necrobiosis lipoidica shows layered granulomas, plasma cells, and little or no mucin.

Question 19Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Henoch-Schönlein purpura is characterized by:

  1. Lobular panniculitis without vasculitis
  2. Granulomatous arteritis with IgG
  3. Leukocytoclastic vasculitis with IgA Correct answer.
  4. Linear IgA at basement membrane

Explanation

Henoch-Schönlein purpura is an IgA-mediated small-vessel vasculitis that shows leukocytoclastic vasculitis with IgA deposits in vessel walls. It typically causes palpable purpura, arthritis, abdominal pain, and glomerulonephritis.

Question 20Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Urticarial vasculitis differs from ordinary urticaria by showing:

  1. Dermal edema without inflammation
  2. Subepidermal blister with eosinophils
  3. Fibrinoid necrosis and leukocytoclasia Correct answer.
  4. Eosinophilic spongiosis

Explanation

Urticarial vasculitis has the histologic features of leukocytoclastic vasculitis, including fibrinoid necrosis and leukocytoclasia, whereas ordinary urticaria shows dermal edema with sparse inflammatory cells. Lesions often last longer than 24 hours and may leave residual pigmentation.

Question 21Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A subepidermal blister with linear IgG at the basement membrane and a u-serrated pattern on salt-split skin is most consistent with:

  1. Epidermolysis bullosa acquisita Correct answer.
  2. Dermatitis herpetiformis with granular IgA
  3. Bullous pemphigoid with mucosal involvement
  4. Pemphigus vulgaris with suprabasal clefting

Explanation

Epidermolysis bullosa acquisita autoantibodies target type VII collagen, so salt-split skin maps the immune deposits to the dermal floor and produces a u-serrated pattern. Bullous pemphigoid targets hemidesmosomal antigens and maps to the epidermal roof.

Question 22Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Livedoid vasculopathy is characterized histologically by:

  1. Hyaline thrombi without true vasculitis Correct answer.
  2. Fibrinoid necrosis with neutrophilic nuclear dust
  3. Palisading granulomas
  4. Subepidermal blister with eosinophils

Explanation

Livedoid vasculopathy shows hyaline or fibrin thrombi in small dermal vessels with endothelial proliferation and little inflammation, reflecting a thrombotic process rather than true vasculitis. Fibrinoid necrosis with nuclear dust indicates leukocytoclastic vasculitis.

Question 23Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

In tuberculoid leprosy, lesions typically show:

  1. Sheets of foamy histiocytes with many bacilli
  2. Well-formed granulomas with few bacilli Correct answer.
  3. Neutrophilic abscesses
  4. Caseating granulomas with Langhans giant cells

Explanation

Tuberculoid leprosy is paucibacillary and shows well-formed, often perineural granulomas with few detectable organisms. Lepromatous leprosy instead shows sheets of foamy histiocytes containing many bacilli.

Question 24Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

Which feature most reliably distinguishes psoriasis from a spongiotic psoriasiform dermatitis?

  1. Granular layer loss with regular acanthosis Correct answer.
  2. Perivascular lymphocytes and melanophages
  3. Focal spongiosis with eosinophils
  4. Parakeratosis with intracorneal neutrophils

Explanation

Psoriasis shows regular acanthosis with clubbed rete ridges, thinning or loss of the granular layer, and little or no true spongiosis. Spongiotic dermatitis retains the granular layer and shows intercellular edema, even when the rete ridges are elongated.

Question 25Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy from a fixed drug eruption lesion typically shows:

  1. Naked noncaseating granulomas with mucin
  2. Interface dermatitis with necrotic keratinocytes Correct answer.
  3. Fibrinoid necrosis with neutrophilic nuclear dust
  4. Subepidermal blister with eosinophils and neutrophils

Explanation

Fixed drug eruption shows interface dermatitis with scattered necrotic keratinocytes, eosinophils, and pigment incontinence. The reaction is often lichenoid and may have a deep perivascular infiltrate.

Question 26Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy of a superficial blister from a patient with no mucosal lesions shows subcorneal acantholysis with intercellular IgG. Which diagnosis is most likely?

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

Explanation

Pemphigus foliaceus targets desmoglein 1 and produces subcorneal acantholysis without mucosal involvement. Intercellular IgG in the epidermis supports an intraepidermal autoimmune blistering disease.

Question 27Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A dermal biopsy shows tightly clustered noncaseating granulomas with a sparse lymphocytic rim in a patient with hilar adenopathy. Which diagnosis is most likely?

  1. Tuberculoid leprosy
  2. Sarcoidosis Correct answer.
  3. Granuloma annulare
  4. Tuberculosis

Explanation

Sarcoidosis classically shows tightly clustered noncaseating granulomas with a sparse lymphocytic rim, often called naked granulomas. This contrasts with caseating granulomas of tuberculosis and the palisading mucin-rich granulomas of granuloma annulare.

Question 28Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy from an edematous erythematous plaque in a febrile neutropenic patient shows a dense neutrophilic infiltrate in the upper dermis without fibrinoid vessel necrosis. Which diagnosis is most likely?

  1. Sweet syndrome Correct answer.
  2. Bullous pemphigoid
  3. Leukocytoclastic vasculitis
  4. Erythema multiforme

Explanation

Sweet syndrome is a neutrophilic dermatosis with dermal edema and a dense neutrophilic infiltrate but no true fibrinoid vessel necrosis. The absence of vessel wall necrosis helps separate it from leukocytoclastic vasculitis.

Question 29Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy from an erythematous, scaly ankle in a patient with chronic venous insufficiency shows spongiosis, dermal hemosiderin, and proliferation of capillaries. Which diagnosis is most likely?

  1. Lichen simplex chronicus
  2. Stasis dermatitis Correct answer.
  3. Psoriasis
  4. Allergic contact dermatitis

Explanation

Stasis dermatitis shows spongiosis with prominent capillary proliferation, hemosiderin deposition, and dermal fibrosis. These changes reflect chronic venous hypertension rather than a primary immune reaction.

Question 30Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A patient with mechanobullous lesions has a subepidermal blister; direct immunofluorescence shows linear IgG at the basement membrane, and on salt-split skin IgG stains the dermal floor. Which diagnosis is most likely?

  1. Epidermolysis bullosa acquisita Correct answer.
  2. Pemphigus vulgaris
  3. Dermatitis herpetiformis
  4. Bullous pemphigoid

Explanation

Epidermolysis bullosa acquisita targets type VII collagen below the lamina densa, so IgG labels the dermal floor on salt-split skin. Bullous pemphigoid antigens are above the lamina densa and label the epidermal roof.

Question 31Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A vulvar biopsy shows a thinned epidermis with a broad band of homogeneous eosinophilic collagen in the papillary dermis and a lymphocytic infiltrate beneath it. Which diagnosis is most likely?

  1. Vitiligo
  2. Lichen simplex chronicus
  3. Lichen planus
  4. Lichen sclerosus Correct answer.

Explanation

Lichen sclerosus features a thinned epidermis, a broad zone of hyalinized papillary dermal collagen, and a lymphocytic band beneath the sclerosis. The hyalinized papillary dermis is the key feature separating it from lichen planus.

Question 32Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy of a crusted papule shows wedge-shaped epidermal necrosis, necrotic keratinocytes, red blood cell extravasation, and a perivascular lymphocytic infiltrate. Which diagnosis is most likely?

  1. Erythema multiforme
  2. Pityriasis lichenoides et varioliformis acuta Correct answer.
  3. Pityriasis rosea
  4. Lichen planus

Explanation

Pityriasis lichenoides et varioliformis acuta shows a wedge-shaped zone of epidermal necrosis with necrotic keratinocytes, red blood cell extravasation, and a lymphocytic infiltrate. These features reflect a lymphocytic vasculopathic process and help distinguish it from ordinary pityriasis rosea.

Question 33Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy of a scaly maculopapular eruption shows psoriasiform epidermal hyperplasia, interface changes, plasma cells, and endothelial swelling. Which diagnosis is favored?

  1. Pityriasis rosea
  2. Lichen planus
  3. Psoriasis
  4. Secondary syphilis Correct answer.

Explanation

Secondary syphilis can mimic many dermatoses, but plasma cells, endothelial swelling, and interface changes are helpful clues. Psoriasis usually lacks plasma cells, and pityriasis rosea shows spongiosis with parakeratosis.

Question 34Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy from a facial plaque shows a dense mixed dermal infiltrate with eosinophils, neutrophils, and leukocytoclasis, but no fibrinoid necrosis of vessel walls, with a Grenz zone. Which diagnosis is most likely?

  1. Sarcoidosis
  2. Leukocytoclastic vasculitis
  3. Sweet syndrome
  4. Granuloma faciale Correct answer.

Explanation

Granuloma faciale shows a mixed dermal infiltrate with eosinophils, neutrophils, and leukocytoclasis, often with a Grenz zone, but true fibrinoid vessel necrosis is absent. Leukocytoclastic vasculitis, by contrast, shows fibrinoid necrosis of vessel walls.

Question 35Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy of an annular erythematous plaque shows a tight perivascular lymphocytic infiltrate in the mid-to-deep dermis with no epidermal spongiosis. Which diagnosis is most likely?

  1. Erythema annulare centrifugum Correct answer.
  2. Tinea corporis
  3. Erythema multiforme
  4. Urticaria

Explanation

Erythema annulare centrifugum shows a tight perivascular lymphocytic infiltrate in the dermis, often described as a coat-sleeve pattern, without epidermal spongiosis. Interface dermatitis and epidermal change point away from this diagnosis.

Question 36Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy of petechial macules on the lower leg shows a lymphocytic perivascular infiltrate, red blood cell extravasation, and hemosiderin in the dermis. Which diagnosis is most likely?

  1. Stasis dermatitis
  2. Pigmented purpuric dermatosis Correct answer.
  3. Livedoid vasculopathy
  4. Leukocytoclastic vasculitis

Explanation

Pigmented purpuric dermatosis shows a lymphocytic perivascular infiltrate with red blood cell extravasation and hemosiderin deposition. It lacks the fibrinoid necrosis of leukocytoclastic vasculitis and the hyaline thrombi of livedoid vasculopathy.

Question 37Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy from a facial papule shows perifollicular lymphohistiocytic inflammation with Demodex mites and occasional granulomas. Which diagnosis is most likely?

  1. Seborrheic dermatitis
  2. Rosacea Correct answer.
  3. Acne vulgaris
  4. Sarcoidosis

Explanation

Rosacea shows perifollicular lymphohistiocytic inflammation with Demodex mites and sometimes granulomatous changes. Acne vulgaris would show comedones and follicular neutrophils, while sarcoidosis shows naked granulomas.

Question 38Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A deep biopsy shows necrotizing inflammation of a medium-sized artery with fibrinoid necrosis and no glomerulonephritis. Which diagnosis is most likely?

  1. Polyarteritis nodosa Correct answer.
  2. Microscopic polyangiitis
  3. Henoch-Schönlein purpura
  4. Leukocytoclastic vasculitis

Explanation

Polyarteritis nodosa is a necrotizing arteritis of medium-sized vessels with fibrinoid necrosis and little or no glomerulonephritis. Leukocytoclastic vasculitis and Henoch-Schönlein purpura affect small vessels, and microscopic polyangiitis often involves glomeruli.

Question 39Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A conjunctival biopsy shows a subepithelial blister with linear IgG and C3 along the basement membrane; the patient has oral erosions and symblepharon. Which diagnosis is most likely?

  1. Mucous membrane pemphigoid Correct answer.
  2. Linear IgA bullous dermatosis
  3. Bullous pemphigoid
  4. Pemphigus vulgaris

Explanation

Mucous membrane pemphigoid produces subepithelial blisters with linear IgG and C3 at the basement membrane and tends to cause mucosal scarring, such as symblepharon. Bullous pemphigoid usually affects skin and is less likely to scar mucosa.

Question 40Inflammatory and Reactive Dermatoses (including interface, spongiotic, psoriasiform, vesiculobullous, granulomatous, and vasculopathic patterns)

A biopsy of an indurated erythematous plaque shows dermal eosinophils and flame figures formed by eosinophilic debris around collagen bundles. Which diagnosis is most likely?

  1. Eosinophilic granulomatosis with polyangiitis
  2. Granuloma faciale
  3. Bullous pemphigoid
  4. Eosinophilic cellulitis Correct answer.

Explanation

Eosinophilic cellulitis (Wells syndrome) shows dermal eosinophils with flame figures, which are eosinophilic debris coating collagen bundles. Granuloma faciale has a mixed infiltrate with a Grenz zone, while Churg-Strauss is a vasculitis.

Question 41Melanocytic Lesions and Melanoma

Which histologic feature most strongly favors a benign melanocytic nevus over melanoma?

  1. Cytologic atypia extending deep into the dermis
  2. Numerous mitoses in the dermal component
  3. Symmetry of the lesion at low magnification Correct answer.
  4. Pagetoid scatter of single melanocytes

Explanation

Benign nevi are generally symmetric and well circumscribed, and they show maturation as melanocytes descend into the dermis. Pagetoid scatter, dermal mitoses, and atypia persisting deep in the lesion are features associated with melanoma.

Question 42Melanocytic Lesions and Melanoma

Melanoma in situ is defined by which finding?

  1. Atypical melanocytes confined to the epidermis Correct answer.
  2. Atypical melanocytes invading the papillary dermis
  3. Melanocytes within the dermis without cytologic atypia
  4. Atypical melanocytes invading the reticular dermis

Explanation

Melanoma in situ consists of a malignant melanocytic proliferation that is restricted to the epidermis and its appendages. Invasion into the papillary or reticular dermis defines invasive melanoma, and dermal melanocytes without atypia do not qualify.

Question 43Melanocytic Lesions and Melanoma

In an intact, non-ulcerated primary melanoma, Breslow thickness is measured from which starting point?

  1. The granular layer of the overlying epidermis Correct answer.
  2. The superficial papillary dermis
  3. The dermoepidermal junction
  4. The basal layer of the epidermis

Explanation

Breslow thickness is measured in millimeters from the granular layer of the epidermis, or from the base of an ulcer when one is present, to the deepest invasive melanoma cell. The measurement must be taken perpendicular to the skin surface.

Question 44Melanocytic Lesions and Melanoma

Which growth pattern is characteristic of nodular melanoma?

  1. Plaque-like growth with epidermal atrophy
  2. Pagetoid spread confined to the epidermis
  3. Vertical growth with little radial growth Correct answer.
  4. Lentiginous radial growth along the junction

Explanation

Nodular melanoma is defined by a prominent vertical growth phase with little or no recognizable radial growth phase. This pattern produces a nodule and often delays diagnosis because the lesion lacks a flat precursor component.

Question 45Melanocytic Lesions and Melanoma

Lentigo maligna typically arises in which clinical setting?

  1. Mucosal surfaces of the oral cavity
  2. Acral skin of young adults
  3. Sun-damaged facial skin of older adults Correct answer.
  4. A giant congenital nevus in infancy

Explanation

Lentigo maligna is a melanoma in situ that develops on chronically sun-damaged skin, most often the face of older adults. It typically begins as an irregular pigmented macule and may progress to invasive lentigo maligna melanoma.

Question 46Melanocytic Lesions and Melanoma

Blue nevi are composed of which cell type?

  1. Dendritic melanocytes within the dermis Correct answer.
  2. Balloon cells with finely vacuolated cytoplasm
  3. Epithelioid melanocytes with Kamino bodies
  4. Nests of melanocytes at the dermoepidermal junction

Explanation

Blue nevi are dermal proliferations of dendritic, heavily pigmented melanocytes that are not connected to the epidermis. The deep pigment scatters light and produces the characteristic blue color.

Question 47Melanocytic Lesions and Melanoma

Kamino bodies are most characteristic of which lesion?

  1. Halo nevus
  2. Spitz nevus Correct answer.
  3. Acral nevus
  4. Blue nevus

Explanation

Kamino bodies are eosinophilic globules composed of basement membrane material found at the dermoepidermal junction in Spitz nevi. They are a helpful clue but are not entirely specific.

Question 48Melanocytic Lesions and Melanoma

Which nuclear marker is widely used to confirm melanocytic lineage?

  1. Desmin
  2. CD3
  3. Cytokeratin 5/6
  4. SOX10 Correct answer.

Explanation

SOX10 is a nuclear transcription factor that is sensitive and relatively specific for melanocytic and schwannian differentiation. It is especially useful when cytoplasmic markers such as Melan-A are lost in desmoplastic or spindle cell melanomas.

Question 49Melanocytic Lesions and Melanoma

Sentinel lymph node biopsy should be discussed for which melanoma?

  1. Clark level II melanoma
  2. Melanoma in situ of the trunk
  3. Breslow thickness 0.9 mm without ulceration Correct answer.
  4. Breslow thickness 0.3 mm without ulceration

Explanation

Sentinel lymph node biopsy is generally offered for melanomas with Breslow thickness of at least 0.8 mm and for thinner ulcerated lesions. Melanoma in situ and very thin non-ulcerated melanomas have a low enough nodal risk that the procedure is not routinely indicated.

Question 50Melanocytic Lesions and Melanoma

How is mitotic rate determined in the dermal component of a primary melanoma?

  1. Mitoses per 100 basal keratinocytes at the junction
  2. Total mitoses in the entire excision divided by tumor area
  3. Mitoses per square millimeter, recorded from the hottest area Correct answer.
  4. Mitoses counted in 10 consecutive high-power fields of the epidermis

Explanation

Mitotic rate is reported as the number of mitoses per square millimeter, counted in the most mitotically active area of the dermal tumor. Standardizing to area allows reproducible comparison between laboratories.