TALL CELL VARIANT OF PAPILLARY THYROID-CARCINOMA - CYTOLOGIC FEATURESAND DIFFERENTIAL DIAGNOSTIC CONSIDERATIONS

The cytologic features of the tall cell variant (TCV) of papillary thy roid carcinoma may be confused with those of other thyroid neoplasms w ith different prognoses and treatment modalities. Education of the cyt omorphology of this variant would be useful in planning treatment for this fairly aggressive variant of papillary carcinoma. The cytologic f eatures of 20 cases of TCV were compared with those of 23 cases of the usual variant (UV) of papillary thyroid carcinoma and of 10 Hurthle-c ell neoplasms (HCN). After a set of features was defined the efficacy of employing it to distinguish TCV from UV and HCN was assessed by thr ee cytopathologists (J.D.T., I.R., and M.O.), who independently examin ed 15 unknown cases selected by the first author. Aspirates of TCV sho wed some specific cytologic features which included large cell size wi th abundant granular cytoplasm and variably sized nuclei with granular chromatin. The cells were sometimes columnar, but more often were pol ygonal, and prominent cytoplasmic borders were present in 50% of cases . Intranuclear inclusions were more prominent in TCV than in UV. There was some overlap in the cytomorphology of some TCV and UV cases, and variable numbers of cells with UV features were encountered in TCV cas es. Employing the cytologic features of TCV listed above, three cytopa thologists examined the unknown cases, which included 7 cases of TCV, 4 cases of UV, and 4 cases of HCN, TCV was recognized as such by all t hree cytopathologists in 6 of 7 cases, and all UV and HCN were correct ly typed by all three examined. The cytologic features of TCV are suff iciently distinctive to enable separation form HCN and most cases of U V. Although the diagnosis of TCV may be rendered employing fine-needle aspiration biopsy material, this diagnosis should be limited, in our opinion, to specimens which contain at least 30% of cells with typical TCV features. (C) 1997 Wiley-Liss, Inc.