# Pilomatrixoma of the Ankle: A Case Report

## TL;DR

A 43-year-old woman had a rare skin tumor called pilomatrixoma on her ankle, which was diagnosed and successfully treated with surgery.

## Contribution

This case report documents pilomatrixoma in an atypical location (the ankle) and emphasizes the need for a multimodal diagnostic approach.

## Key findings

- Pilomatrixoma was diagnosed in a rare location (the ankle) using MRI, fine-needle biopsy, and histopathology.
- Surgical excision with clear margins led to no recurrence after six months.
- The case highlights the importance of considering pilomatrixoma in subcutaneous nodule differential diagnoses.

## Abstract

Pilomatrixoma, also known as calcifying epithelioma of Malherbe, is a rare benign skin tumor originating from hair follicle matrix cells. It typically presents as a firm, painless subcutaneous nodule, most commonly found in the head, neck, and upper extremities. Pilomatrixoma can occasionally appear in atypical locations, posing a diagnostic challenge due to its nonspecific clinical presentation. A 43-year-old female presented with a painless, slowly enlarging mass on the lateral side of her left ankle, which had been present for approximately one year. Physical examination revealed a firm, well-circumscribed subcutaneous nodule measuring about 2 cm in diameter with normal overlying skin. An MRI of the left ankle demonstrated a well-circumscribed, subcutaneous mass with heterogeneous signal intensity, consistent with calcifications, suggesting pilomatrixoma. A fine-needle aspiration biopsy confirmed the presence of basaloid cells, shadow cells, and areas of calcification. The lesion was surgically excised, and histopathological examination validated the diagnosis of pilomatrixoma. The patient had an uneventful postoperative course, with no recurrence at the six-month follow-up. This case underscores the importance of considering pilomatrixoma in the differential diagnosis of subcutaneous nodules, even in unusual locations. A comprehensive diagnostic approach, including clinical evaluation, imaging, and histopathological examination, is essential for an accurate diagnosis. Surgical excision with clear margins is the treatment of choice, ensuring low recurrence rates and excellent patient outcomes. This report enhances the understanding of pilomatrixoma and highlights the necessity for a multimodal diagnostic strategy in managing this rare condition effectively.