# Case report: thigh hidradenoma masquerading as lipoma

## TL;DR

A 35-year-old man had two thigh lumps, one of which was initially thought to be a lipoma but was later diagnosed as a rare hidradenoma.

## Contribution

This case highlights the diagnostic challenge of hidradenomas mimicking lipomas and emphasizes the importance of histopathology for accurate diagnosis.

## Key findings

- One of the lumps was confirmed as a hidradenoma through histopathology, despite initial clinical suspicion of lipoma.
- Hidradenomas are rare and can be misdiagnosed clinically, requiring surgical excision for definitive diagnosis.
- Complete excision with clear margins is crucial to prevent recurrence or malignant transformation.

## Abstract

Hidradenomas are benign adnexal neoplasms, which were recently been subdivided into two groups: eccrine differentiation (poroid hidradenomas) or apocrine differentiation (clear cell hidradenomas) with the latter being rarer. These types of tumors have been associated with recurrence and malignant transformation; however, recurrence and malignancy are considered very rare. We present a case report of a 35-year-old male who presented with two lumps, clinically representing simple lipomas but one of them turned to be a hidradenoma. A 35-year-old gentleman not known to have any medical illnesses and surgically free, presented to our general surgery clinic complaining of two slow-growing (over 3 years) painless lumps, one in the right upper thigh and the other one in the left shoulder. The patient denied any previous history of trauma or infection nor any history of discharge or overlying skin changes, and there were no clinical features that might suggest the presence of malignancy. Upon examination, both lumps were firm, freely mobile, non-tender, intact overlying skin, with no skin changes, and no regional lymphadenopathy. Prior to excision, our preliminary impression was lipoma for both masses. Surgical excision was carried out with clear margins; each mass was labeled separately, and specimens were sent for histopathology. Histopathological diagnosis of the left shoulder mass was consistent with lipoma; however, the right upper thigh mass turned to be a hidradenoma. Hidradenomas are uncommon benign neoplasms with varied types. Recurrence and transformation into malignancy have been reported in some cases. Complete surgical excision with negative margins and further follow-up with the patient are crucial to prevent such consequences. Clinical diagnosis can be difficult; however, the management is the same with surgical removal as it will give us the definitive diagnosis with the pathology report.