Cytodiagnosis of well differentiated hepatocellular carcinoma - Can indeterminate diagnoses be reduced?

BACKGROUND. Distinction of well differentiated hepatocellular carcinoma (KC C) from benign hepatocellular lesions is a well recognized problem in fine- needle aspiration (FNA) cytology, sometimes leading to indeterminate report s. The aim of this study was to critically examine criteria that might allo w definitive diagnosis in these cases. METHODS. FNA smears and cell blocks from 65 patients with primary hepatocel lular lesions were reviewed. Seventy separate samples had been obtained. Th e initial reports in these samples were: HCC in 34, benign findings in 27, and indeterminate findings in 9. We defined architectural and cytological f eatures seen in the malignant cases but not seen in the benign cases, inclu ding an assessment of reticulin in cell blocks. These criteria were then ap plied to the indeterminate cases. RESULTS. The most specific cytologic criteria of malignancy in well differe ntiated HCC were (i) numerous stripped atypical nuclei, (ii) macronucleoli, (iii) increased mitoses, and (iv) multinucleation. The most specific archi tectural criteria in smears were (i) widened trabeculae, (ii) well defined capillaries traversing tissue fragments, and (iii) solid islands of hepatoc ytes rimmed by endothelial cells. The most valuable architectural criteria in cell blocks were (i) trabeculae greater than two cells thick and (ii) re duced or absent reticulin framework. Using the above criteria a retrospecti ve diagnosis of HCC was possible in eight of the nine indeterminate cases, all but one of which have subsequently been confirmed as malignant. CONCLUSIONS. Close attention to architectural features in both smears and c ell blocks should allow most well differentiated HCCs to be diagnosed by FN A cytology. A reticulin stain should be part of the routine assessment of c ellblocks. Cancer (Cancer Cytopathol) 1999;87:270-7. (C) 1999 American Canc er Society.