Radiologic features of posterior mediastinal leiomyosarcoma presenting as a mimic of peripheral nerve sheath tumor

Rationale. Leiomyosarcoma (LMS) is one of the most common subtypes of malignant mesenchymal neoplasms, accounting for approximately 20% of all new cases of soft tissue sarcomas. While LMS is more commonly found in the abdomen, retroperitoneum, large blood vessels, and uterus, it is exceptionally rare in the mediastinum, with fewer than 10% of documented cases in the literature. LMS can closely mimic more common peripheral nerve sheath tumors (PNSTs), which makes its diagnosis challenging. Given its proximity to critical neural structures, it can lead to neurological deficits, such as radiculopathy and sensory loss, complicating management. Case description and diagnosis. We present a case of a 62-year-old male patient with no significant medical history, who was brought in with a six-month history of progressively worsening back pain. Magnetic resonance imaging (MRI), conducted in view of the clinical presentation, revealed imaging features of a posterior mediastinal peripheral nerve sheath tumor. However, biopsy results indicated positive immunohistochemical markers for leiomyosarcoma. This case highlights the importance of distinguishing LMS from PNSTs in a clinical setting, with particular attention to neurological manifestations. Conclusions. Due to their variable presentation and considerable risk for metastasis, leiomyosarcomas pose challenges in diagnosis and treatment. Early imaging, neurological assessment, and histopathological confirmation are critical to minimize neurological sequelae, and crucial for proper management and prognosis evaluation.