Introduction. Primary leiomyosarcoma of bone is rarely described in the literature. In young patients, the clinical and radiological features may mimic relatively common tumours like osteosarcoma. Vertebral and nodal metastasis from osseous leiomyosarcoma is extremely uncommon. Case presentation. A 25-year-old female presented with progressively increasing pain and swelling of the right knee. Clinical and radiological features were suggestive of osteosarcoma. Pre-operative biopsy showed a malignant spindle cell tumour. The surgical resection specimen showed features of leiomyosarcoma of the right proximal tibia. On further evaluation, the patient was found to have an L3-L4 vertebral lesion and histopathological evaluation showed a similar tumour. After 11 months of initial presentation, the patient had axillary lymph node metastasis. Conclusion. Primary osseous leiomyosarcoma should be considered as a differential diagnosis even in young patients presenting with meta-diaphyseal expansile malignant bony lesions. Histology and ancillary studies can confirm the diagnosis.
Keywords: bone; leiomyosarcoma; lymph node; metastasis.