Case of the Month

A 27-year-old woman presents with a tender nodule in the pubic area. Has been growing for the past 14 months. It bleeds with trauma and is slightly tender. She is otherwise healthy.

Here are the pathology micrographs, courtesy of Erick Jacobson-Dunlop, MD, board certified dermatopathologist

What's Your Diagnosis?

Diagnosis: Hidradenoma, nodular (pigmented)

By Karyn Alana Haitz BA, Susan Burgin MD, Lowell A. Goldsmith MD, MPH (from VisualDx.com, of which Dr Crutchfield is a dermatology editor)

Nodular hidradenoma is a rare, benign adnexal tumor that displays apocrine differentiation in the majority of cases (clear cell hidradenoma) and eccrine differentiation (poroid hidradenoma) in the remainder. The two histopathologic types are indistinguishable clinically. A 0.5-3 cm firm nodule develops on the head, anterior trunk, or upper limbs, or any other cutaneous site less frequently. It grows slowly and may ulcerate.

Nodular hidradenoma is more common in females and can occur in any ethnicity and at any age including infancy, although it is most common in the fourth decade of life. There are currently no known risk factors. Local recurrence can also occur, especially with inadequate surgical excision.

Hidradenocarcinoma is a very rare malignant tumor that can arise from nodular hidradenoma, although it typically arises de novo.

Therapy

Complete surgical excision is recommended to differentiate hidradenoma from the even rarer hidradenocarcinoma, which may have a similar clinical presentation. Also, local recurrence of nodular hidradenoma may occur if the lesion is not excised completely. Rarely, a hidradenocarcinoma can arise from a nodular Hidradenoma. Mohs micrographic surgery is an initial option for larger tumors, and may also be employed for recurrent tumors.

Reference

Hidradenoma, nodular (pigmented) www.VisualDx.com