Extraskeletal Mesenchymal Chondrosarcoma, a Rare Entity with Unusual Metastases: A Case Report.

Introduction: Extraskeletal mesenchymal chondrosarcoma (ESMC) is rare, aggressive, and high grade malignant tumors originating from soft tissues. It carries a poor prognosis with a tendency for local recurrence and distant metastasis, necessitating long-term follow-up. The most common sites for metastasis are the lungs, bones, and lymph nodes. Meanwhile, pancreatic metastases are extremely rare.

Case description: A 35-year-old female presented with a history of wide local excision for the left upper limb mass; histopathology showed ESMC. She was on surveillance with a computed tomography scan of the thorax and magnetic resonance imaging of the left upper limb at 3-months intervals until she developed vertebral and pancreatic lesions after 6 months post-surgery. No pulmonary metastases were noted. Considering the unusual site for metastasis and to exclude the possibility of any second malignancy, bone biopsy, and endoscopic ultrasound-guided fine-needle aspiration was performed that confirmed metastases. Later she developed osseous metastases in the pelvis and femora.

Practical implication: Pancreatic metastasis from ESMC is extremely rare. In case of new visceral or osseous lesions in a patient with a past medical history of ESMC, the possibility of metastatic disease should be considered. A biopsy can be performed to confirm the diagnosis.