Lipomas Eroding Adjacent Bone: Report of Three Cases.

Introduction: Lipomas are common benign masses of variable size that may be found in a variety of superficial and deep tissues. As a benign growth, lipomas do not typically invade into adjacent structures such as bone. However, when a lipoma has grown large enough, several studies have noted bony erosion in adjacent bony structures. In this series of cases, we report three instances where a large lipoma caused adjacent bony erosion and describe the respective imaging findings. Case Report: A 57-year-old woman had a left gluteal mass eroding the outer surface of the ilium; a 68-year-old man with a recurrent right buttock lipoma demonstrated similar erosion of the posterior ilium; and a 79-year-old woman had a multilobulated lipoma extending through the scapula from posterior to anterior. In all cases, imaging revealed well-defined, homogenous lipomatous masses with adjacent osseous scalloping best visualized on computed tomography. Histopathology confirmed benign lipomatous tumors with fat necrosis and no evidence of malignancy. Conclusion: Large, deep lipomas, though benign, can rarely cause pressure-induced erosions of adjacent bony structures. Recognizing this atypical presentation is crucial to avoid misdiagnosis as a malignant tumor and to guide appropriate surgical management.