ABPath Dermatopathology 1 — Questions and Answers
Question 1: Which pattern of inflammation is characterized by lymphocytes lined up along the dermal-epidermal junction with associated vacuolar change and dyskeratotic keratinocytes?
- Psoriasiform
- Interface (Correct answer)
- Perivascular
- Granulomatous
Correct answer: Interface
Interface dermatitis is defined by lymphocytes at the dermal-epidermal junction with vacuolar alteration and dyskeratotic (necrotic) keratinocytes, as seen in lichen planus and lupus.
Question 2: A skin biopsy shows parakeratosis, regular acanthosis with elongated rete ridges, and collections of neutrophils in the stratum corneum (Munro microabscesses). This is most consistent with:
- Lichen planus
- Psoriasis (Correct answer)
- Seborrheic dermatitis
- Pityriasis rosea
Correct answer: Psoriasis
Psoriasis classically shows Munro microabscesses (neutrophil collections in the stratum corneum), regular acanthosis with elongated rete ridges, and parakeratosis with suprapapillary plate thinning.
Question 3: In a non-ulcerated melanoma, Breslow thickness is measured from:
- The granular layer to the deepest tumor cell (Correct answer)
- The skin surface to the deepest tumor cell
- The dermal-epidermal junction to the deepest tumor cell
- The base of the epidermis to the base of the tumor
Correct answer: The granular layer to the deepest tumor cell
Breslow thickness is measured from the top of the granular layer (or the base of an ulcer if ulcerated) to the deepest invasive tumor cell.
Question 4: Which histologic feature best supports a diagnosis of Spitz nevus over melanoma in a pediatric patient?
- Presence of Kamino bodies (Correct answer)
- High mitotic rate at the base
- Nuclear pleomorphism
- Pagetoid spread throughout epidermis
Correct answer: Presence of Kamino bodies
Kamino bodies — eosinophilic PAS-positive globules at the dermal-epidermal junction — are characteristic of Spitz nevi and are a helpful benign feature distinguishing them from melanoma.
Question 5: A biopsy shows atypical keratinocytes involving the full thickness of the epidermis without dermal invasion. This is best classified as:
- Invasive squamous cell carcinoma
- Basal cell carcinoma
- Squamous cell carcinoma in situ (Bowen disease) (Correct answer)
- Actinic keratosis
Correct answer: Squamous cell carcinoma in situ (Bowen disease)
Full-thickness epidermal atypia without breach of the basement membrane is the hallmark of squamous cell carcinoma in situ, also known as Bowen disease.
Question 6: Which immunohistochemical marker is MOST useful in distinguishing dermatofibrosarcoma protuberans (DFSP) from dermatofibroma?
- S100
- CD34 (Correct answer)
- Melan-A
- CK5/6
Correct answer: CD34
DFSP is characteristically CD34-positive while dermatofibroma is CD34-negative (often factor XIIIa-positive), making CD34 the key discriminating marker between these two fibroblastic tumors.
Question 7: Paget disease of the breast skin is histologically characterized by:
- Malignant squamous cells infiltrating the epidermis
- Large cells with pale cytoplasm and prominent nucleoli infiltrating the epidermis (Correct answer)
- Atypical melanocytes spreading throughout the epidermis
- Neutrophils causing intraepidermal pustules
Correct answer: Large cells with pale cytoplasm and prominent nucleoli infiltrating the epidermis
Mammary Paget disease shows large atypical glandular cells with abundant pale cytoplasm and prominent nucleoli infiltrating the epidermis, reflecting an underlying ductal adenocarcinoma.
ABPath Dermatopathology 1
Which pattern of inflammation is characterized by lymphocytes lined up along the dermal-epidermal junction with associated vacuolar change and dyskeratotic keratinocytes?