Limiting the diagnosis of atypical small glandular proliferations in needle biopsies of the prostate by the use of immunohistochemistry

Prostatic biopsies containing small glandular formations suspicious of, but not diagnostic for, carcinoma represent a diagnostic dilemma, as they cann ot be definitely identified as either benign or malignant. The term 'atypic al small acinar proliferation' (ASAP) in the differential diagnosis of carc inoma has recently evolved considerable discussion. This study has tried to assess the biological potential of ASAP by further immunohistochemical (TH C) analysis. Biopsy-proven cases of ASAP (n = 114) n ere analysed, in which consecutive sections still contained the suspicious lesion. LHC studies we re undertaken with anti-cytokeratin 34 beta E12 and the proliferation marke r MIB-1, Staining with 34 beta E12 revealed a complete basal cell lever in 25 casts (21.9%), a fragmented layer in 58 cases (50.9%), and absence of ba sal cells in 31 cases (27.2%). MIB-1 labelling indices (LIs) in these three groups were significantly higher than in benign prostatic tissue (p<0.001) and reached the level of low-grade prostatic carcinoma (p>0.05), The suspi cious morphology of ASAP on haematoxylin and eosin-stained slides mas suppo rted by the finding of elevated proliferative activity. Subgroups were reve aled bg immunohistochemical assessment of basal cell status and cases witho ut basal cells were diagnosed as carcinoma. Nevertheless, rebiopsy is recom mended if radical surgery is planned, to exclude insignificant cancer. Case s with a complete or fragmented basal cell layer were regarded as non-malig nant. Whether a fragmented basal cell layer reflects a technical artefact o r transition to carcinoma is unknown, but the proliferative activity of bot h lesions was increased and corresponded to that of low-grade prostatic car cinoma. In these cases, therefore, at least clinical follow-up is strongly recommended and repeat biopsies are encouraged, Copyright (C) 2000 John Wil ey & Sons, Ltd.