Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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October 5, 2023
Skull Parosteal Lipoma With Reactive Hyperostosis
Background:
- Parosteal lipoma is a benign fatty neoplasm with extensive relationship with the periosteum. The lesion shows contiguity with underlying bone instead of primarily originating from bone.
Clinical Presentation:
- Presents as slow-growing, painless, soft-tissue mass abutting the bone
Key Diagnostic Features:
- Most frequent site is long bones; skull is extremely rare
- MRI is modality of choice with characteristic features of lipoma along with hyperostotic bone. No periosteal reaction.
- Classified into 4 variants on basis of underlying ossification:
- Type I: No ossification
- Type II: Pedunculated exostosis
- Type III: Sessile exostosis
- Type IV: Patchy chondro-osseous modulation
Differential Diagnoses:
- Well-differentiated liposarcoma: This is ill-defined with presence of calvarial erosion, intracranial invasion, and enhancing soft-tissue component. Liposarcoma has thick enhancing septae as compared with thin septae in parosteal lipoma. Parosteal lipoma is fairly well-defined without calvarial erosion and intracranial invasion.
Treatment:
- Surgical resection with shaving of reactive hyperostosis
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