Hidradenomas are benign sweat gland tumors that typically present as small nodules in adulthood. Their anatomic distribution is wide and rarely includes acral sites. In this setting, reliable separation from digital papillary adenocarcinoma is important, but notoriously difficult. Hematoxylin and eosin–stained sections of 25 hidradenomas on acral skin were retrieved. The clinical presenting features and morphologic findings were recorded, and follow-up was obtained. Immunohistochemistry was performed for AE1/3, CK5/6, EMA, CEA, SMA, S100, p40, and p63. The tumors presented as solitary nodules on the hands (n=17) and feet (n=8) of adults (age range: 20 to 81 y; median: 50 y), with an equal sex distribution. Histologically, the well-circumscribed tumors were lobular, with a solid and cystic growth within dermis. Duct and squamous differentiation and vascularized hyaline stroma were frequent. The majority (n=18) were poroid hidradenomas. Scattered cytologic atypia and mitotic activity (median: 2/10 HPF) were common, and a pseudoinfiltrative growth of strands in a hyaline to sclerotic matrix was noted in 5 tumors. No papillary structures, atypical mitoses, or tumor necrosis were present. Immunohistochemically, all tumors expressed AE1/3, CK5/6, p40, and p63 strongly and diffusely. Luminal differentiation was highlighted by epithelial membrane antigen and carcinoembryonic antigen staining. S100 and SMA staining was absent. Follow-up (1 to 288 mo; median: 61 mo), available for 20 patients, showed no local recurrences and no disease-related mortality. Acral hidradenomas and digital papillary adenocarcinomas share a well-circumscribed dermal growth pattern containing solid, cystic, and tubular areas with mitotic activity and at least focal cytologic atypia. Lack of papillary structures and the diffuse positivity for p40 and p63 in the absence of S100 and SMA expression are helpful features in favor of acral hidradenoma.

Background: Endogenous vitamin D synthesis can be affected by a number of variables, including skin colour, amount of skin exposed and levels of ultraviolet radiation. The objective of this study was to assess the feasibility of using only sunlight exposure in Canada to meet the daily recommended level of vitamin D, given differences in these variables and adherence to guidelines for sun protection.Methods: Ultraviolet index data for 13 Canadian sites were obtained from Environment Canada. The sun exposure times required to synthesize 1000 IU of vitamin D in fair-and dark-skinned people who exposed either 1/4 or 1/8 of their body surface area to the sun were calculated for each hour of the year. These times were then classified according to whether the ultraviolet index was 3 or more (when sun protection is advised) or less than 3. Results:During the fall and winter months and in the more northern sites, ultraviolet radiation levels were too low for all skin types to use sun exposure alone to obtain enough vitamin D within one time period. The required exposure time became longer when a smaller surface area was exposed. For people with darker skin, it can be difficult even in the summer to find opportunities outside of when sun protection is advised to use sunlight to obtain the recommended dose of vitamin D.

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Cellular neurothekeoma is a benign cutaneous neoplasm that typically occurs on the head, neck, and upper body of young adults with a slight female predominance. It is a rare lesion to diagnose and multiple neurothekeomas in one patient are even more uncommon finding. We present a case of multiple neurothekeomas in a middle‐aged woman with lower extremity involvement and summarize the current literature on multiple neurothekeoma patients. A 46‐year‐old female presented with nearly one dozen skin‐colored papules on the head, upper limb, and lower limb. The lesions were clinically diagnosed as dermatofibromas and a nevus. Eight lesions were biopsied and confirmed to be cellular neurothekeomas, with one initially misinterpreted on histology as a dermatofibroma. Awareness of cellular neurothekeoma as a diagnostic entity and the possibility of atypical presentations as seen in our case (eg, in multiple numbers, in older adults, and on the lower extremity) are important in allowing for accurate clinical and histological diagnosis of these lesions. The possibility of a syndromic association with multiple cellular neurothekeomas should be explored further.

Deep penetrating nevus (DPN) is an uncommon acquired melanocytic lesion with a distinct histopathological appearance that typically behaves in an indolent manner. The lesion is characterized by a symmetrical proliferation of epithelioid to spindled melanocytes associated with abundant melanophages and wedge-shaped extension to the deep reticular dermis and subcutis. Pronounced cytologic atypia and mitotic figures are usually absent, which helps distinguish DPN from melanoma with a deep penetrating growth pattern. Recently, the concept of atypical DPN has been proposed for lesions that demonstrate borderline histomorphologic features and may be associated with lymph node deposits but lack the copy number aberrations typical of melanoma by either fluorescence in situ hybridization or comparative genomic hybridization. While most of these lesions have a favorable clinical course, rare lesions may progress to melanoma. In this review, we summarize the current literature on atypical DPNs with uncertain behavior/metastatic potential and outline the characteristics that distinguish these lesions from conventional DPN and melanoma with DPN-like features.