Dermatology MCQ - Infiltrative and Neoplastic Disorders - Stucco keratosis

A 72-year-old man presents with multiple, small, white-to-light-gray, "stuck-on" papules on the dorsal aspects of his feet and ankles. The lesions are dry, rough to the touch, and can be easily scraped off with a fingernail without causing bleeding. He reports they have been slowly increasing in number over the years. The rest of his skin examination is unremarkable. What is the most likely diagnosis and the underlying histopathological hallmark?

A. Disseminated superficial actinic porokeratosis (DSAP), characterized by a cornoid lamella.
B. Verruca plana, characterized by koilocytosis and hypergranulosis.
C. Stucco keratosis, characterized by hyperkeratosis and a "church-spire" pattern of epidermal papillomatosis.
D. Lichen planus, characterized by a saw-tooth pattern of acanthosis and a band-like lymphocytic infiltrate.
E. Guttate hypomelanosis, characterized by a decrease in melanin and melanocytes.

Correct Answer: C. Stucco keratosis, characterized by hyperkeratosis and a "church-spire" pattern of epidermal papillomatosis.

Answer and Explanation

The correct answer is C. This question describes the classic presentation of stucco keratosis. The key clinical clues are the location (distal extremities, especially ankles and dorsal feet), the multiple, small, white/gray, "stuck-on" appearance, and the fact they can be easily scraped off. The name derives from their resemblance to droplets of stucco plaster. Histologically, they are characterized by marked hyperkeratosis and a specific pattern of epidermal papillomatosis that resembles "church spires" or "skyscrapers."

Why the Other Options are Incorrect:

• A. Disseminated superficial actinic porokeratosis (DSAP): DSAP presents as brownish-red, annular, atrophic macules or patches with a characteristic raised, thread-like border. They are located on sun-exposed limbs and are not easily scraped off. The histopathological hallmark is the cornoid lamella, a thin column of parakeratosis.

• B. Verruca plana (Flat warts): These are caused by HPV and are typically skin-colored or tan, flat-topped papules. They are most common on the face and dorsal hands. They are not typically described as white, dry, and "stuck-on," and histology shows koilocytes (vacuolated keratinocytes).

• D. Lichen planus: This is an inflammatory condition presenting as violaceous, flat-topped, polygonal papules, often with a fine scale and Wickham's striae. It is typically pruritic and not easily scraped off. The histology shows a dense, band-like lymphocytic infiltrate.

• E. Guttate hypomelanosis (Idiopathic Guttate Hypomelanosis): This presents as small, porcelain-white, well-defined macules, not papules. They are depigmented and completely flat, lacking any scale or "stuck-on" quality.

Additional High-Yield Information for Exams:

• Histopathology: Stucco keratosis is a variant of seborrheic keratosis. Its specific features include:

  • Hyperkeratosis: Thickened stratum corneum, often with a basket-weave pattern.

  • Papillomatosis: Elongation of the rete ridges, but in a specific, narrow, "church-spire" or "skyscraper" pattern.

  • Mild Acanthosis: Thickening of the epidermal layer.

  • It lacks the horn pseudocysts and significant pigmentation of a classic seborrheic keratosis.

• Differential Diagnosis: As outlined above, the main differential includes other small, discrete papules on the extremities. The key is the unique clinical appearance and location.

• Associated Conditions & Prognosis:

  • Benign Nature: Stucco keratoses are entirely benign with no malignant potential.

  • Epidemiology: They are very common in older men and are considered a sign of photoaging and dry skin.

  • Prognosis: Excellent. They are a cosmetic concern only.

• Management & Rationale:

  • Rationale: The goal is to confirm the benign diagnosis and provide management options if the patient desires treatment for cosmetic reasons.

  • First-line: Clinical diagnosis and reassurance. No treatment is necessary.

  • Treatment Options: If treatment is requested, it is very effective and simple due to the superficial nature of the lesions.

    • Light Curettage: The lesions can be easily and painlessly scraped off with a curette, often without the need for anesthesia.

    • Light Cryotherapy: A very brief freeze time is sufficient.

    • Emollients: Regular use of moisturizers can sometimes soften the appearance and make them less noticeable.