BACKGROUND: Clear cell change, which may occur in a variety of thyroid neoplasms, is an uncommon finding. A fine needle aspirate of a follicular neoplasm showing extensive clear cell morphology is even more rarely described in the literature. CASE: We report the fine needle aspiration cytology of a case of follicular neoplasm undergoing clear cell change due to intracellular accumulation of lipid and mucin. The cytology showed cohesive sheets of nondescript, round to oval cells having ample, pale-staining cytoplasm. Many of the tumor cells tended to cluster around branching capillaries. Adipocytelike cells with discrete cell borders, eccentric nuclei and cytoplasm distended by fat globules were frequently found. The cell block sections also showed scattered ghost outlines of these adipocytelike cells in a mucoid background. Similar findings were noted in the crush preparation of the freshly excised surgical specimen. Histologic examination confirmed the presence of a minimally invasive follicular carcinoma with clear cell change. CONCLUSION: Though the cytologic features of this peculiar morphologic variant of follicular neoplasm may mimic those of mesenchymal lesions or metastatic tumors, recognition of other subtle changes, together with ancillary investigations, is useful in arriving at a correct preoperative diagnosis.
BACKGROUND: Clear cell change, which may occur in a variety of thyroid neoplasms, is an uncommon finding. A fine needle aspirate of a follicular neoplasm showing extensive clear cell morphology is even more rarely described in the literature. CASE: We report the fine needle aspiration cytology of a case of follicular neoplasm undergoing clear cell change due to intracellular accumulation of lipid and mucin. The cytology showed cohesive sheets of nondescript, round to oval cells having ample, pale-staining cytoplasm. Many of the tumor cells tended to cluster around branching capillaries. Adipocytelike cells with discrete cell borders, eccentric nuclei and cytoplasm distended by fat globules were frequently found. The cell block sections also showed scattered ghost outlines of these adipocytelike cells in a mucoid background. Similar findings were noted in the crush preparation of the freshly excised surgical specimen. Histologic examination confirmed the presence of a minimally invasive follicular carcinoma with clear cell change. CONCLUSION: Though the cytologic features of this peculiar morphologic variant of follicular neoplasm may mimic those of mesenchymal lesions or metastatic tumors, recognition of other subtle changes, together with ancillary investigations, is useful in arriving at a correct preoperative diagnosis.