No abstract

Schwannomas are benign peripheral nerve sheath neoplasms composed almost entirely of Schwann cells and are diagnosed histopathologically by the presence of singular architectural patterns called Antoni A and Antoni B areas. These were described first in 1920 by the Swedish neurologist Nils Antoni. The Antoni A tissue is highly cellular and made up of palisades of Schwann cell nuclei, a pattern first described in 1910 by the Uruguayan neuro-pathologist Jose Verocay and are known as Verocay bodies. This article describes the structure and appearance of Verocay bodies and Antoni A and B areas with a brief biographical introduction of the men who described these patterns.

Nine patients, seven males and two females aged 6-14 years, presented with extensive, asymptomatic, brown-black macules and mildly elevated, pigmented lesions of a few months' duration. The sites affected were the face, trunk and proximal extremities. The skin lesions were discrete and individual lesions were less than 2 cm in size. The clinical diagnoses rendered by the referring physicians were lichen planus pigmentosus, urticaria pigmentosa, erythema dyschromicum perstans and postinflammatory hyperpigmentation. Histology in all nine cases showed papillomatosis of the dermis with prominent pigmentation of the basal layer (pigmented papillomatosis) without any significant dermal inflammation. Two cases had spores of Pityrosporum ovale in the thickened horny layer, one of which also had, in addition, bacterial colonies in the stratum corneum. The pigmentation resolved on its own over several months. This presentation is similar to the previously described idiopathic eruptive macular pigmentation with the additional histological finding of papillomatosis that is being described for the first time and may be nosologically related to acanthosis nigricans and confluent and reticulate papillomatosis.

Porokeratosis is an uncommon disorder of keratinization that presents with keratotic papules or annular plaques that expand centrifugally with a thread-like elevated border. A distinctive histologic structure, the cornoid lamella, is diagnostic of this disorder and consists of a column of parakeratosis with the absence of the granular layer and dyskeratotic cells in the upper spinous zone. Porokeratosis confined to the genitogluteal region is rare and may be subclassified into three types, namely, classical porokeratosis on the genital region, ptychotropic porokeratosis most often seen in the natal cleft and buttocks and penoscrotal porokeratosis that is seen on the penis and adjacent scrotal skin in young men in their third decade of life. Genitogluteal porokeratosis is usually pruritic and may be undiagnosed for several years as it does not resemble classical porokeratosis in many cases; however, a biopsy is diagnostic. In general, response of genital porokeratosis to any modality of treatment is disappointing. No malignant changes have hereto been reported in porokeratosis restricted to the genitogluteal region.