[A case of primary chondrosarcoma difficult to differentiate from retroperitoneal tumor].

A 57-year-old woman was admitted with chief complaints of pain in the right lower quadrant and weight loss. Contrast computed tomography of the abdomen revealed a tumor in the right inferior aspect of the liver. The patient was diagnosed with cystic renal cell carcinoma or lymphangioma, and she underwent surgery. The tumor was approached via upper abdominal midline incision and was found to be immobile. The tumor had adhered tightly to the right 12th rib and was resected along with the 12th rib. Gross pathology of the resected tissue revealed a jelly-like component inside, and the patient was histopathologically diagnosed with chondrosarcoma (grade 1). The patient is currently undergoing outpatient follow-up; a 1-year postoperative follow-up did not show any recurrence or metastasis. Chondrosarcoma accounts for approximately 20% of primary malignant bone tumors. It has a low response rate to both chemotherapy and radiotherapy, and surgical treatment remains the most effective method. Bone tumors must be considered in cases of atypical retroperitoneal tumors in which a definitive diagnosis cannot be made using diagnostic imaging.