Liposarcoma With Hibernoma-like Histology: A Clinicopathologic Study of 16 Cases

Hibernoma is an uncommon benign tumor of brown fat cells that consistently expresses uncoupling protein 1 (UCP1). Herein, we clinicopathologically characterized 16 liposarcomas, for which histology, at least focally, closely resembled that of hibernoma, including sheets of brown fat-like, finely multivacuolated-to-eosinophilic tumor cells with no or minimal nuclear atypia. The cohort consisted of 4 well-differentiated liposarcomas (WDLSs), 6 dedifferentiated liposarcomas with a concomitant WDLS component, and 6 myxoid liposarcomas (MLSs). For all dedifferentiated liposarcoma cases, hibernoma-like histology was present only in the WDLS component. All tumors presented as large, deep-seated masses. Hibernoma-like histology resembled the pale cell, mixed cell, eosinophilic cell, or spindle cell subtypes of hibernoma, and it was a focal observation, with conventional liposarcoma histology coexisting in all cases. However, a few biopsy samples were predominated by hibernoma-like patterns, and 1 case was initially interpreted as hibernoma. Hibernoma-like components in WDLS immunohistochemically coexpressed MDM2 and CDK4 in most cases and harbored MDM2 amplification in tested cases, whereas half of the cases expressed UCP1. The hibernoma-like components of MLS expressed DDIT3, and DDIT3 rearrangements were present in the tested cases, whereas only negative or equivocal UCP1 expression was observed. In summary, WDLS and MLS focally demonstrate hibernoma-like histology on rare occasion...

Source: The American Journal of Surgical Pathology - September 23, 2022 Category: Pathology Tags: Original Articles Source Type: research