# Fibro-Osseous Pseudotumor Presenting as Calcified Subcutaneous Mass Over the Achilles Tendon in a Five-Year-Old Girl

## TL;DR

A rare benign tumor called fibro-osseous pseudotumor was diagnosed in a child with a calcified mass near the Achilles tendon.

## Contribution

This case report adds to the limited literature on fibro-osseous pseudotumors in children and highlights diagnostic challenges.

## Key findings

- A calcified subcutaneous mass near the Achilles tendon was surgically removed and confirmed as a fibro-osseous pseudotumor.
- Histopathology showed fibrous tissue with osteoid formations, supporting the diagnosis.
- Imaging techniques like X-ray, MRI, and CT scan were crucial for diagnosis.

## Abstract

A calcified mass located in the subcutaneous area above the Achilles tendon of a child poses difficulty for a correct diagnosis. Differential diagnosis includes tumoral calcinosis, calcified fibroma, calcified tendinitis, and myositis ossificans. A fibro-osseous pseudotumor is a rare benign lesion that usually affects the digits. Histologically, it consists of fibrous tissue with areas of osteoid formation.

We report a child with a hard subcutaneous mass above the Achilles tendon. Radiographic assessment, including X-ray, MRI, and CT scan, revealed a calcified tumor in the posterior part of the Achilles tendon, in proximity to the sural nerve and vessel. After surgical removal of the mass, histopathology revealed fibrous connective tissue with areas of islands and trabeculae of osteoid, confirming the diagnosis of a fibro-osseous pseudotumor. A subcutaneous calcified mass in a child requires appropriate clinical and pathological investigation to ensure an accurate diagnosis.