Cytodiagnosis of colonic adenoma: morphology and clinical importance

This is a retrospective review of 74 colonic brushings with a view to identify colonic adenomas and recognize the cytologic features of villous adenoma (VA) and tubular adenoma (TA). Smears were reviewed for overall field pattern as well as individual cellular changes. The results were tabulated and analyzed for differences and similarities. The most distinguishing feature of adenoma was the presence of isolated and clustered elongate "needle" and "fan" cells as first described by Thabet. These were more abundant and in papillary cluster formations in VA as opposed to clusters of more blunted configuration in TA. Another striking feature of VA was an abundance of elongated benign naked needle nuclei in the background. Smears from some cases of TA revealed isolated and clustered needle cells in low numbers but almost no naked nuclei. Tubulovillous adenoma (TVA) showed features of VA on brush cytology. A hemorrhagic diathesis was distinctly more prominent in VA than in TA. However, focally some red cells were noted in smears from TA. The patterns of TA and VA were otherwise essentially similar with regard to cellularity, individual cell sizes, N/C ratios, and nuclear appearance.