# Primary Osseous Leiomyosarcoma of Talus Mimicking Idiopathic Transient Osteoporosis: A Case Report and Literature Review

## TL;DR

A rare case of bone cancer in the talus was initially mistaken for a benign condition, highlighting the need for careful diagnosis to avoid mismanagement.

## Contribution

This case report highlights the diagnostic challenge of early-stage primary osseous leiomyosarcoma of the talus mimicking idiopathic transient osteoporosis.

## Key findings

- Initial MRI findings of LMSB mimicked idiopathic transient osteoporosis, leading to misdiagnosis.
- Local recurrence occurred despite wide resection and reconstruction, necessitating amputation.
- Prompt surgical resection is crucial for LMSB, contrasting with conservative treatment for idiopathic transient osteoporosis.

## Abstract

Primary leiomyosarcoma of the bone (LMSB) is an exceptionally rare malignant bone tumor. We report a case of a 60-year-old woman with LMSB of the talus initially misdiagnosed as idiopathic transient osteoporosis of the talus based on clinical and initial MRI findings, which showed extensive bone marrow edema without soft tissue invasion. Despite initial improvement with off-loading treatment, the patient's symptoms recurred, and subsequent imaging revealed progression and soft tissue involvement. A biopsy confirmed grade 1-2 leiomyosarcoma. Wide resection and reconstruction with a custom-made total talar prosthesis were performed, but local recurrence necessitated a transtibial amputation eight months postoperatively. This case highlights the diagnostic challenge of early-stage LMSB of the talus, which can mimic idiopathic transient osteoporosis on MRI. Clinicians should be aware of this potential pitfall, as the treatment strategies for these two conditions are diametrically opposed: conservative management for idiopathic transient osteoporosis versus prompt surgical resection for LMSB to improve prognosis. Repeated imaging and a high index of suspicion are crucial for timely and accurate diagnosis of this rare and aggressive tumor.