Malignant histological transformation in surgically excised lipomas larger than 5 cm

Background: Lipomas are benign tumors commonly presenting as soft-tissue masses. Lipomas exceeding 5 cm in diameter may pose a challenge regarding their potential malignancy. Methods: We analyzed 73 consecutive patients undergoing surgical excision for lipomas greater than 5 cm. Clinical, demographic, and histopathological data were reviewed. Tumor localization was categorized based on regions subject to high mechanical friction (neck, axillae, knees, and legs) compared with abdominal or low-friction areas. Results: Of the 73 cases initially diagnosed clinically as benign lipomas, histopathological analysis identified malignancy in 14 cases (19.2%), exclusively located in high-friction regions. Malignant cases predominantly comprised well-differentiated liposarcomas (n = 10), dedifferentiated liposarcomas (n = 3), and one case of pleomorphic liposarcoma. No malignancies were identified in abdominal (low-friction) locations. Conclusions: The significant association between tumor location in regions of high mechanical friction and the incidence of malignancy underscores the potential role of mechanical stress in malignant transformation.