Cryptococcal Lung Infection Simulating Metastasis in a Myxoid Liposarcoma Patient: A Case Report

Myxoid liposarcoma is a soft tissue sarcoma with a high tendency for lung metastasis. Its aggressive nature necessitates accurate diagnosis and treatment planning to improve outcomes.

A 31-year-old man presented with a three-year history of an asymptomatic, progressively enlarging mass in his right thigh. Magnetic resonance imaging indicated a soft tissue tumor within the sartorius muscle, and an incisional biopsy suggested myxoid liposarcoma. Staging computed tomography scans revealed two nodules in the right lung, leading to an initial diagnosis of Stage IV myxoid liposarcoma. Given his overall health and the presumed resectability of the lesions, the patient underwent three courses of preoperative chemotherapy with doxorubicin and ifosfamide. Follow-up imaging showed no change in the size of the tumor or lung nodules. A wide resection of the thigh tumor was performed, including part of the vastus medialis, sartorius, and gracilis muscles. Postoperatively, 65 gray (relative biological effectiveness) of proton radiation therapy was administered. Subsequently, a robot-assisted thoracoscopic right lower lobectomy and lymph node dissection were performed to resect the lung nodules. Histological examination of the lung lesions revealed necrotizing granulomas with numerous round-shaped yeasts. The special stains confirmed pulmonary cryptococcosis, ruling out metastasis and revising the tumor staging to Stage Ib. Consequently, postoperative chemotherapy was canceled, and the patient showed no recurrence over 3 years of follow-up.

This case emphasizes the need for histopathological evaluation of lung lesions in sarcoma patients, as not only cryptococcosis but also various fungal infections can mimic metastasis, potentially altering the treatment plan and prognosis.