# Extraskeletal Intramuscular Chondroma of the Knee – Case Report and Review of the Literature

## TL;DR

This paper reports a rare case of a cartilage tumor in the knee muscle and highlights the challenges in diagnosing it correctly.

## Contribution

The paper presents a rare case of extraskeletal intramuscular chondroma in the knee with a detailed diagnostic process.

## Key findings

- The tumor was initially misdiagnosed as a benign fatty tumor based on imaging.
- Histopathological examination confirmed the diagnosis of extraskeletal intramuscular chondroma.
- Surgical excision led to a complete recovery without recurrence.

## Abstract

Extraskeletal chondromas are small nodular cartilaginous lesions not attached to bone or the periosteum. They are rare tumors commonly occurring in the hands and feet. The objective of the present study is to describe a case of extraskeletal intramuscular chondroma (EIC) in the left knee and the diagnostic challenges faced by us.

A 25-year-old female patient presented with slow-growing swelling in the left knee for 2 years. Clinically, the swelling was arising from the quadriceps muscle. We considered possibilities such as rhabdomyoma, neurofibroma, and intramuscular lipoma. Imaging studies suggested a benign fatty tumor. She was treated by excision. Microscopy was consistent with EIC without recurrence.

A rare entity, clinically, EIC can mimic other benign soft-tissue tumors. Histopathology exams can provide a definitive diagnosis. The excision of the tumor is curative.

Os condromas extraesqueléticos são pequenas lesões cartilaginosas nodulares que não estão aderidas ao osso ou ao periósteo. São tumores raros que ocorrem comumente nas mãos e nos pés. Objetivo deste artigo é descrever um caso de condroma intramuscular extraesquelético (CIE) no joelho esquerdo e os desafios diagnósticos que enfrentamos.

Uma paciente de 25 anos apresentou um edema de crescimento lento no joelho esquerdo havia 2 anos. Clinicamente, o edema era proveniente do músculo quadríceps. Foram consideradas possibilidades como rabdomioma, neurofibroma, e lipoma intramuscular. Os estudos de imagem sugeriram um tumor de gordura benigno. A paciente foi tratada com a excisão cirúrgica. A microscopia indicou CIE sem recorrência.

O CIE é uma lesão rara. Clinicamente, pode ter aspecto semelhante ao de outros tumores benignos dos tecidos moles. A histopatologia pode fornecer um diagnóstico definitivo. A excisão cirúrgica do tumor é curativa.