ABSTRACT
Pseudohyperplastic prostatic adenocarcinoma is a rare histologic variant of prostatic adenocarcinoma that resembles benign nodular hyperplasia. Immunohistochemistry can verify the absence of basal cells, but it is frequently admixed with conventional adenocarcinoma. Because fine needle aspiration cytology is rarely performed in primary prostatic adenocarcinoma, the cytology of the pseudohyperplastic variant has not been described. We experienced a case of metastatic pseudohyperplastic adenocarcinoma in a pulmonary nodule of 75-year-old man. The cytologic smear was mostly composed of large, flat sheets with elongated branching papillae in a clean background. The sheets showed a well-defined honeycomb appearance of tall columnar, regularly arranged monotonous cells with little cytologic atypia. In subsequent prostatic biopsy, pseudohyperplastic variants were identified together with conventional adenocarcinoma of Gleason's grade 3 and 4. The cytologic features of pulmonary nodules were identical to those of pseudohyperplastic components of prostatic adenocarcinoma.