Fine needle aspiration cytology of a dedifferentiated liposarcoma - Reportof a case with histologic and immunohistochemical follow-up

BACKGROUND: Dedifferentiation is a Histologic progression of a neoplasm fro m low grade to high grade histology. It occurs ill tumors of the retroperit oneum and in those undergoing treatment. This usually occurs in the setting of radiation or chemotherapy or as a spontaneous process over a long perio d. The features of dedifferentiation can be toward any mesenchymal element of the underlying neoplastic process. CASE: We report the cytologic features of a dedifferentiated liposarcoma ar ising in a 76-year-old man who had a history of well-differentiated liposar coma. Papanicolaou- and Diff-Quik-stained smears from a radiologically guid ed fine needle aspiration biopsy showed a hypercellular sample. The smears showed a mixed population of cells. There were multinucleated, pleomorphic giant cells with abundant cytoplasm, smaller clusters of cells with a high nuclear/cytoplasmic ratio and cells with spindled and elongated nuclear fea tures. The follow-up surgical resection specimen showed a dedifferentiated liposarcoma with strong and diffuse immunoreactivity to vimentin, desmin an d CD68 in the large, pleomorphic cells; focal and weak immunoreactivity to smooth muscle actin and S-100 in these cells; and strong and focal immunore activity to desmin, smooth muscle actin and muscle-specific actin in the sp indle cells. This supports the dedifferentiated components oft his tumor to be of fibrohistiocytic and leiomyosarcomatous differentiation. CONCLUSION: Dedifferentiation of a well-differentiated liposarcoma should b e entertained in the setting of a mass lesion in the retroperitoneum in pat ients with prior histories of well-differentiated liposarcorma. The radiolo gic features of a particular neoplastic process can be very helpful in dete rmining the nature of this process.