Sclerosing Adenosis-Like Lesion of Sweat Glands

To the Editor[colon] Sclerosing adenosis is a relatively common proliferative lesion of the breast, derived from the terminal duct[ndash]lobular unit (1). Histologically, it is composed of elongated and compressed proliferating tubules, embedded in a dense cellular stroma. Tubules are lined by two types of cells[colon] epithelial cells, which may show varying degrees of atrophy, and myoepithelial cells, which may be markedly reduced in number or absent (1,2). Although many benign and malignant lesions of sweat glands have been reported to have analogous counterparts in the breast (3,4), sclerosing adenosis-like lesions of sweat glands have not yet been documented. A 40-year-old female patient came to surgical visit for a slightly raised, verrucous cutaneous lesion of the scalp in her temporal region. A biopsy sample was taken of the lesion, clinically diagnosed as nevus sebaceous, and was submitted to the Dermatopathology Section of S.M. Annunziata Hospital (Florence). Histologically, the lesion appeared to be a complex one, composed of a nevus sebaceus associated with a junctional lentiginous melanocytic nevus. The epidermis appeared hyperplastic and showed marked papillomatosis. Numerous mature sebaceous glands, intermingled with mature apocrine glands, occupied the dermis. In a paracentral area, an increased number of junctional nonatypical melanocytes, mostly arranged in single units, rarely forming small nests, were observed in elongated rete ridges. In two small areas, located at the opposite extremes of the specimen, elongated, compressed, sometimes dilated tubular structures appeared to be embedded in a desmoplastic stroma (Figs. 1 and 2), strongly reminiscent of sclerosing adenosis occurring in mammary glands. FIG. 1.: Sclerosing adenosis-like lesion of sweat glands (lesion 1)[colon] the lesion, located beneath the epidermis, appears as a nodular area composed of tubular structures in a desmoplastic stroma (H[amp]E [times]100). FIG. 2.: Sclerosis adenosis-like lesion of sweat glands (lesion 2)[colon] tubules, sometimes dilated embedded in a desmoplastic stroma, close to sebaceous glands (H[amp]E [times]400). Homologies between sweat glands and mammary glands, generally explained by the similar embryologic origin of such glands, are numerous and well documented. Several benign lesions of sweat glands closely resemble similar lesions of the breast[colon] apocrine glands and apocrine hidrocystoma resemble apocrine metaplasia of the breast; eccrine spiradenoma appears to be quite similar to mammary eccrine spiradenoma-like tumor (5); syringocystadenoma papilliferum seems to mimic nipple adenoma (florid papillomatosis) (6); and syringomatous carcinoma of sweat glands is histologically very similar, if not identical, to syringomatous adenoma of the nipple (7) and to syringomatous carcinoma of the breast (8). Moreover, ductal carcinoma, apocrine carcinoma, mucinous carcinoma, and adenoid cystic carcinoma of sweat glands (9) are indistinguishable from the analogous carcinomas of the breast. The occurrence of sclerosing adenosis-like lesions in sweat glands, previously not recorded, represents a further analogy between sweat glands and mammary glands. Sclerosing adenosis-like lesion of sweat glands must be distinguished from some benign and malignant cutaneous lesions, which may show similar histologic characteristics. Syringoma is composed of numerous small ducts, embedded in a fibrous stroma (10); ducts, however, have small commalike tails, which give them a tadpole appearance (10), and the stroma is less desmoplastic. Syringomatous carcinoma is composed of tubules, sometimes with tadpole appearance, solid islands, and horny cysts in a desmoplastic stroma; neoplastic proliferation, however, is not well defined and often deeply infiltrates the subcutaneous fat and muscular structures (11). Ductal carcinoma of sweat glands is characterized by ductal structures and solid cords of atypical polygonal cells haphazardly infiltrating the dermis or deeper (3). Carmelo Urso M.D. Chiara Anichini M.D.