Anatomic Pathology: Skin Pathology

706) An 8-year-old boy presents with numerous flat-topped, skin-colored papules on the back of his hands. A biopsy specimen of the lesion is shown. The BEST histologic diagnosis is:

• Verrucae plana, also known as flat warts, are caused by HPV infection, usually HPV-3 and HPV-10. Patients present with multiple small, flat-topped, tan or skin-colored papules, most commonly on the back of the hands or face.

• On histologic examination, verrucae plana demonstrate basket-weave hyperkeratosis and acanthosis, with diffuse vacuolation of the cells of the granular and upper spinous layers with pyknotic nuclei, creating a “bird’s eye” appearance of the cells. Hypergranulosis is common.

• In contrast to classic verrucae vulgaris, verrucae plana demonstrate absent or minimal papillomatosis and parakeratosis.

• Spontaneously regressing verrucae plana may show a superficial lymphocytic infiltrate with lymphocyte exocytosis and apoptosis of cells in the epidermis.

• Verrucae plana may clinically and histologically resemble lesions of epidermodysplasia verruciformis, a genetic disorder that predisposes to HPV infection (including HPV-3, HPV-5, and HPV-8) and to squamous cell carcinomas. The flat warts seen in epidermodysplasia verruciformis infection are usually more persistent and widespread than verrucae plana. Although the histologic appearance may resemble verrucae plana, the lesions of epidermodysplasia verruciformis usually demonstrate large cells in the granular and spinous layers. The cells have a blue-gray cytoplasm, a clear nucleoplasm, and a perinuclear halo. Keratohyaline granules may be prominent.

Nuovo GJ, Ishag M: The histologic spectrum of epidermodysplasia verruciformis. Am J Surg Pathol 2000;24(10):1400-1406.

Stierman S, Chen S, Nuovo G, et al: Detection of human papillomavirus infection in trichilemmomas and verrucae using in situ hybridization. J Cutan Pathol 2010;37(1):75-80.

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