Dedifferentiated Liposarcoma with Meningothelial-Like Whorls: A Diagnostic Challenge on Biopsy

Abstract

Dedifferentiated liposarcoma (DDL) is a malignant adipocytic tumor characterized by the juxtaposition of a well-differentiated liposarcoma and a nonlipogenic sarcomatous component. The presence of meningothelial-like whorls is a rare histological pattern that may complicate diagnosis, especially on small biopsies. Case Presentation: We report a case of a 60-year-old man presenting with a 5 cm inguinal mass. Histological examination of a core biopsy showed a spindle cell neoplasm arranged in meningothelial-like whorls. Immunohistochemistry revealed positivity for smooth muscle actin (SMA), p16, CD10, and CD99, with a Ki-67 proliferative index of approximately 25%. Molecular analysis confirmed MDM2 gene amplification. No well-differentiated liposarcoma component was identified. The diagnosis of dedifferentiated liposarcoma with meningothelial-like whorls was established based on the combined histologic, immunohistochemical, and molecular findings. Conclusion: This case highlights the diagnostic challenge of identifying DDL on biopsy specimens lacking a differentiated lipogenic component. The meningothelial-like whorl pattern may mimic other spindle cell tumors. Demonstration of MDM2 amplification is essential for accurate diagnosis.