Pleomorphic Liposarcoma Cytologically Detected in Hemosiderotic Pleural Effusion: Pitfalls Mitigated by Cytologic Clues and Cellblock Immunocytochemistry

Abstract

ABSTRACTSarcomatous serous effusions are uncommon and diagnostically challenging. Dedifferentiated and pleomorphic liposarcomas are rare tumors in pleural effusions revealing highly pleomorphic tumor cells mimicking carcinoma, mesothelioma, melanoma, and other sarcomas. Hematothoracic effusions further complicate the cytologic diagnosis. Correct cytologic recognition is important. We report pleomorphic liposarcoma cytologically detected in effusion fluid in a 56‐year‐old man who presented with a massive unilateral pleural effusion. ThinPrep showed hemorrhagic effusion fluid characterized by lysed red blood cells, foamy macrophages, and siderophages intermixed with highly pleomorphic predominantly naked mononuclear and giant nuclei. The aggregated siderophages and vacuolated macrophages could be mistaken for tumor cells, whereas the bare nuclei may be missed as nonspecific degenerate changes. Cellblock sections showed highly pleomorphic mononuclear and multinucleated giant tumor cells with diagnostic lipoblasts, intermixed with foamy macrophages and siderophages. Cellblock immunocytochemistry showed staining for vimentin and S‐100 protein in the tumor cells. Other lineage‐specific immunomarkers were negative. CD68 and calretinin revealed frequent background macrophages and scarce mesothelial cells. The tumor cells were negative for MDM2 and CDK4. The entertained cytopathologic diagnosis was pleomorphic liposarcoma. Core needle biopsy was procured from the mass. The histopathologic features and immunoprofile of the tissue specimen matched the cytopathologic and immunocytochemical findings confirming the cytologic diagnosis of pleomorphic liposarcoma. Pleomorphic liposarcoma is an unexpected cytologically challenging finding in effusions, particularly when compounded by pitfalls introduced by hemosiderotic fluid. Attention to certain cytologic clues mitigate pitfalls. Cellblock is a valuable diagnostic tool when integrated with relevant negative and positive immunocytochemical markers.