Abstract
BACKGROUND: Atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDL) is a rare low-grade malignant tumor primarily composed of adipose tissue. Although lipomatous tumors commonly develop in the subcutaneous tissues, those originating from the chest wall are infrequently reported. Accurate diagnosis and appropriate treatment are essential, given the tumor's potential for local recurrence despite its low metastatic risk. CASE PRESENTATION: We report the case of a 45-year-old man with a firm, enlarging, and painless mass in the left anterior lower chest wall. Imaging revealed a well-defined, fat-attenuated mass (4.8 × 5.0 × 5.2 cm) located in the left precardial subcostal space. Incisional biopsy suggested a lipomatous neoplasm. Thoracoscopic-assisted total removal excision was performed. Histopathological analysis showed mature adipose tissue with stromal cell atypia and muscle infiltration. Immunohistochemistry was negative for MDM2 and CDK4. Due to close microscopic margins and the tumor's deep location, adjuvant radiation therapy was administered. The final diagnosis was ALT. No recurrence was noted at the about 2-year follow-up, and the patient reported excellent postoperative quality of life. CONCLUSION: ALT of the chest wall is rare, and its management requires accurate diagnosis, complete resection, and consideration of adjuvant therapy when margins are close. This case contributes to the limited literature on subcostal ALT and emphasizes a multidisciplinary approach.