A Case Report and Literature Review on a Primary Dedifferentiated Liposarcoma of the Gallbladder.

Primary dedifferentiated liposarcoma (DDLPS) of the gallbladder is an exceptionally rare neoplasm. We present a case of incidentally discovered gallbladder DDLPS identified during routine surveillance abdominal computed tomography (CT) in a patient with a history of low-grade papillary urothelial carcinoma of the bladder. The mass was initially suspected to be primary gallbladder carcinoma, prompting cholecystectomy. Histopathologic examination revealed a high-grade sarcomatous nodule within the gallbladder adventitia, sharply demarcated from an adjacent well-differentiated liposarcoma (WDLPS) component. The diagnosis of DDLPS was confirmed by fluorescence in situ hybridization (FISH) demonstrating MDM2 gene amplification. This case expands the limited literature on gallbladder DDLPS and emphasizes the importance of including liposarcoma in the differential diagnosis of atypical gallbladder masses. Recognition of this rare entity is critical for appropriate diagnosis, surgical decision-making, and patient management.