To the Editor:
Hidradenoma papilliferum is a benign adnexal tumor, mainly affecting the anogenital skin of middle-aged women (1). It is usually a slow-growing cystic dermal mass, that can be either asymptomatic or ulcerate and bleed. There have been 17 reports on extragenital hidradenoma papilliferum, which Vang and Cohen called “ectopic hidradenoma papilliferum” (2). These tumors affected different areas of the skin and are slightly more frequent in women.
We report a new case of ectopic hidradenoma papilliferum, the second in the world literature affecting the back. A 48-year-old woman consulted on a slow-growing 2 cm nodule on the upper third of her back. She was completely asymptomatic and could not recall when the tumor had first appeared. The surgeon decided to excise the tumor with a preoperative diagnosis of dermal cyst. The patient showed no evidence of disease recurrence at 6 months follow-up.
Microscopic examination revealed a 2-cm cystic dermal nodule that had been completely excised with a narrow rim of subcutaneous fat. The cyst wall was lined by an epithelium showing apocrine features and foci of squamous cell metaplasia. Papillae and micropapillae projected from the cyst wall into the cavity (Fig. 1). The papillae had a broad fibrous core, focally showing infiltration by plasma cells and lymphocytes (Fig. 2), mainly at the periphery of the nodule. There were two different layers of cells in the papillae: one basal layer of small cells and one luminal layer with larger cells (Fig. 3). All these pathologic findings were consistent with hidradenoma papilliferum.
Hidradenoma papilliferum is a slow-growing benign adnexal tumor, mainly affecting the anogenital skin of middle-aged women (3). To our knowledge, there has only been one report on a perianal hidradenoma papilliferum in a man (4). This tumor originates in apocrine glands, what explains its typical anogenital location. There are some pathogenically similar lesions arising in the nipple area, although they are usually named papillary adenomas, rather than hidradenomas (5).
There have been 17 reports on hidradenoma papilliferum affecting extragenital skin (2,6–12) (Table 1). The most frequent location has been the head and neck area (11 cases), followed by the extremities (upper, 3 cases; lower, 2 cases). We have found only one case, apart from the one we herein report, of a hidradenoma papilliferum in the back of a 63-year-old woman (2). It has been postulated that these ectopic lesions arise in modified apocrine glands, like Moll glands of the lid. However, in our case we found neither ectopic apocrine glands in the adjacent skin, that could have been the origin of the tumor, nor any epidermal changes suggesting nevus sebaceous of Jaddasohn.
Ectopic hidradenoma papilliferum are slightly more frequent in women (10 women and 7 men, 2:1) and the age range has been wide (8–78 years). Similar to its anogenital counterpart, most ectopic lesions were asymptomatic and had grown for a long time before resection. Despite occasional reports on malignization of anogenital hidradenomas papilliferum (2), all the ectopic lesions have behaved in a benign fashion and have not recurred or metastasized.
A prominent feature in our case was the existence of focal areas infiltrated by plasma cells and lymphocytes. This finding was also reported by Vang and Cohen and Schewach-Millet in their cases that considered them signs of a mixed differentiation between hidradenoma papilliferum and syringocystadenoma papilliferum, two closely related tumors.
M.J. Fernández-Aceñero, M.D.
T. Aramendi Sánchez, B.S.
M.C. Villanueva Sánchez, B.S.
L. Requena, M.D.
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