Perineural invasion, mucinous fibroplasia, and glomerulations - Diagnosticfeatures of limited cancer on prostate needle biopsy

The diagnosis of prostate cancer on needle biopsy is based on a constellati on of histologic features. There are, however, three histologic findings th at are diagnostic of prostate carcinoma: perineural invasion (PNI), mucinou s fibroplasia, and glomerulations. We prospectively identified core needle biopsies during a 5-month period in which one of these three entities was t he key diagnostic feature of carcinoma within the biopsy specimen. Of 1480 consult cases reviewed, the following were key features to the diagnosis of very limited carcinoma: PNI (n = 9; 0.6%), mucinous fibroplasia (n = 2; 0. 1%), and glomerulations (n = 0). To assess the incidence of PNI as the key feature, we also analyzed reports from Dianon during a 1-year period. Of ap proximately 16,300 Dianon needle biopsies with cancer, 12 (0.07%) cases had PNI as the key diagnostic feature. Six of these 12 cases were also consult cases. Of the total of 15 cases with PNI, cancer was limited with 11 of th e cases showing involvement of only one nerve. The median number of glands per nerve was five (range, 1-15). In addition to PNI, malignant cytologic f eatures included amphophilic cytoplasm in 11 of 11 assessable cases and nuc lear enlargement and hyperchromasia in 11 of 15 cases. Other malignant feat ures were limited. Twelve cases showed rare to no visible nucleoli. Two cas es had eosinophilic intraluminal debris. Blue mucin, crystalloids, and mito ses were absent in all cases. Nine of the 15 cases of PNI and the two cases of mucinous fibroplasia were verified as carcinoma with immunohistochemist ry using high molecular weight cytokeratin. In rare cases, PNI is virtually the sole finding necessary to establish the diagnosis of carcinoma on need le biopsy. Although mucinous fibroplasia and glomerulations are also consid ered diagnostic of carcinoma, their occurrence alone without more conventio nal forms of carcinoma is even more rare.