Recurring Hidradenocarcinoma of the Lower Extremity

Hidradenocarcinomas are rare adnexal tumor of the sweat glands. They are typically found on the head and neck with a high rate of recurrence and metastasis. Here, we present a case of a 67-year-old woman who presented with long-standing subcutaneous mass over her right knee. She underwent initial surgical excision with positive margins, and histopathology of the resection specimen was consistent with hidradenocarcinoma. The patient completed 60-Gray adjuvant radiation to the surgical bed postoperatively. Eight months later, the patient returned with a concern for recurrence of the hidradenocarcinoma at the same site. Biopsy confirmed the recurrence, and the malignancy was excised with 2-cm margins along with surgical reconstruction with a local muscle flap. She has not had recurrence at follow-up 1 year after the reconstructive flap. This case highlights the histopathologic nature of hidradenocarcinomas and that, despite local excision and large-dose radiation, malignancy can recur.