Hidradenocarcinomas are rare, aggressive adnexal tumors of sweat gland origin that demonstrate a high potential for local recurrence, metastasis and poor outcome. These neoplasms can derive from preexisting clear cell hidradenomas, but more commonly appear de novo with the molecular events responsible for the pathogenesis currently unknown. Molecular markers of pathogenesis as well as effective forms of adjuvant chemotherapy are missing due to the lack of accurate diagnosis, paucity of cases and confusion with other visceral solid tumors. Here, we report a 37-year-old man who presented with a rapidly growing, painful palpable mass located in the right inguinal area. The patient was a nonsmoker, did not consume alcohol and had a medical history remarkable only for a lower abdominal superficial skin lesion in the same area that had been excised 11 years earlier. Although initially slow growing, the lesion eventually expanded, was surgically excised and was diagnosed as a hidradenoma. There was no family history of malignancy and the patient had not experienced any constitutional symptoms. We probed the immunohistochemical status and detected negative staining for the estrogen, progesterone and Her2 receptors, while strong, diffuse nuclear staining was seen in the majority of cells consistent with p53 overexpression. Similarly, strong nuclear reactivity was seen with p63 and p73 antibodies. The p63 gene contains 2 separate promoters which express at least 6 major transcripts that lead to 2 fundamentally different classes of proteins; 3 isoforms (TAp63α, β and γ) encode proteins that induce apoptosis, whereas the other 3 isoforms (ΔNp63α, β and γ) may exert inhibitory effects on p53. Interest in p63 stems from this ‘two genes in one’-concept. Importantly, the nuclear presence of ΔNp63 was detected widespread throughout the tumor. We have identified a subtype of hidradenocarcinomas that express ΔNp63 and uncovered an unforeseen commonality with triple-negative breast tumors. To our knowledge, this is the first report of a sweat gland tumor that displayed expression of both ΔNp63 and p73 and demonstrated a triple-negative receptor status. Such a link between 2 seemingly disparate tumor types indicates a mutual pathway of tumorigenesis and suggests the potential for common therapeutic regimens.

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