Abstract:

Hidradenomas are sweat gland tumors of apocrine or eccrine differentiation. Their malignant counterpart, hidradenocarcinoma, is quite rare, accounting for only six percent of malignant eccrine cancers. These commonly present as subcutaneous nodules in women between the ages of 50 and 70. They often occur on the scalp or face and are ulcerated or pruritic. There is a propensity for lymph node metastasis and, as such, sentinel lymph node biopsies are considered. Treatment includes wide local excision as well as chemo- and/or radiotherapy, depending on metastasis. Prognosis is varied, with a 10-50% chance of local recurrence after wide local excision. The 5-year survival is 30%. We discuss a 27-year-old African American female who presented with a small nodule on the right parietal scalp, of approximately three months’ duration. Gross examination showed a cystic nodule. The initial biopsy was diagnosed as a squamous cell carcinoma in situ and underlying cyst. It was noted, however, that there were portions of neoplasm which displayed nuclear pleomorphism and rare mitotic figures. There was evidence of duct formation in the cystic portion, as well as eosinophilic hyaline stroma. The lesion showed infiltration into the dermis. A malignant hidradenoma was favored. A return visit six weeks later showed significant growth clinically with palpation of a discrete nodule. Microscopic sections showed epidermal ulceration with a pleomorphic, mitotically active, dermal proliferation of atypical pale-staining keratinocytes growing in a lobular pattern and extending into the subcutaneous fat. This infiltrative lesion had cystic spaces with areas of focal necrosis. Focal ductal formation was identified. Epidermal involvement was limited. A CT scan showed no underlying bony involvement or adenopathy. Molecular studies found relevant biomarkers were ATM LOH, ATM deletion, CHEK1 LOH, CHEK1 deletion, and CDKN2A deletion. The lesion extended to the deep margin and awaits re-excision.

Financial Disclosure:
No current or relevant financial relationships exist.

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Katherine Jerew, MD