# A rare case of giant myopericytoma of the lower limb: a case report and review of the literature

## TL;DR

A 15-year-old girl in China had a rare, large myopericytoma tumor in her thigh, the biggest reported in Asia, which was correctly diagnosed and treated with surgery.

## Contribution

Reports the largest myopericytoma in the lower limb in Asia and highlights diagnostic challenges due to its atypical size and features.

## Key findings

- The tumor measured 8.5 cm, much larger than the typical <2 cm size of myopericytomas.
- Histopathology confirmed the diagnosis after initial suspicion of synovial sarcoma.
- Surgical excision is the definitive treatment and avoids mismanagement due to the tumor's rarity.

## Abstract

Myopericytoma (MPC) is a rare soft tissue tumor that typically occurs in the extremities or distal limbs. These tumors are usually slow-growing, painless, and measure <2 cm on average. While generally benign, they can lead to complications if misdiagnosed. Surgical excision is the definitive treatment.

A 15-year-old female from southern China presented with a painless mass in her right thigh, which had persisted for three years. Imaging revealed a mass measuring approximately 8.5 cm, initially suspected to be a synovial sarcoma. Magnetic resonance imaging (MRI) showed a large, irregular soft tissue mass adjacent to the lower femur with heterogeneous signal intensity. Surgical excision was performed, and histopathological analysis confirmed the diagnosis of MPC.

MPC is rare and often misdiagnosed owing to its nonspecific clinical and radiological features. This case is notable for the size of the mass, which exceeds the typical size of MPCs, making it the largest reported case of lower extremity MPC in Asia. A definitive diagnosis is made through histopathological examination, and surgical excision remains the gold standard treatment. Given its rarity, early recognition and accurate diagnosis are essential to avoid mismanagement.

This case highlights the rarity of MPC and underscores the necessity of comprehensive diagnostic evaluation. Surgical excision is essential for symptom resolution and complication prevention.

•This report presents a rare case of a giant myopericytoma (8.5 cm) in the lower extremity, the largest in Asia.•MPC diagnosis is challenging due to atypical size, deep location, and cyst-solid components mimicking other tumors.•Surgical resection is the primary treatment for MPC, with histopathology as the diagnostic gold standard.•The rarity and imaging nonspecificity of MPC necessitate long-term clinical follow-up.

This report presents a rare case of a giant myopericytoma (8.5 cm) in the lower extremity, the largest in Asia.

MPC diagnosis is challenging due to atypical size, deep location, and cyst-solid components mimicking other tumors.

Surgical resection is the primary treatment for MPC, with histopathology as the diagnostic gold standard.

The rarity and imaging nonspecificity of MPC necessitate long-term clinical follow-up.