A SPECTRUM OF CYTOMORPHOLOGIC VARIATIONS IN MEDULLARY-THYROID CARCINOMA - FINE-NEEDLE ASPIRATION FINDINGS IN 19 CASES

BACKGROUND, Medullary thyroid carcinoma (MTC), a rare malignancy with a variety of morphologic appearances, can mimic both primary and metas tatic lesions of the thyroid gland and give rise to diagnostic problem s when these tumors are aspirated. Although cytopathologic features of MTC have been well described, this study was undertaken to define and elaborate further, subtle morphologic variations, the recognition of which would be helpful in the diagnosis of MTC. METHODS. A retrospecti ve review of 19 cases of histologically confirmed MTC was conducted. F ine-needle aspirations were performed by endocrinologists or cytopatho logists using a 23- or 25-gauge needle. Smears were stained with Diff- Quik, Papanicolaou, or hematoxylin and eosin (H&E) stain. Cell blocks were routinely prepared, and 4-micron sections were stained with H&E. RESULTS. Certain cytologic features, such as eccentric nuclei, neuroen docrinelike nuclei, inconspicuous nucleoli, binucleation and multinucl eation, ill-defined cytoplasmic borders, and a clean background, were present in all cases. Additional helpful features seen in some but not in all cases included syncytial groups of cells, round to oval and sp indle shapes, dendritic cell processes, the presence of amyloid, and n uclear molding and grooves. CONCLUSIONS, The authors found that MTC co uld be adequately diagnosed by fine-needle aspiration, despite the fre quent cytomorphologic variations, based on a set of features consisten tly present in all the cases included in this study. Features such as neuroendocrinelike chromatin and nuclear molding have not been previou sly described. (C) 1997 American Cancer Society.