Argyrophilic adenocarcinoma of the prostate with Paneth cell-like granules

A prostatic adenocarcinoma with argyrophilia and many Paneth cell-like granules in a 91-year-old man is reported. The initial symptom was pollakisuria, and the laboratory data showed no significant abnormality except for moderate anemia. Through radiologic examinations a right hydronephrosis and metastatic cancer of the lumbar vertebra were suspected. Because prostatic cancer was suspected, a needle biopsy of the prostate was performed. Routine histologic examinations revealed a moderately differentiated adenocarcinoma of the prostate. By hematoxylin and eosin stain, eosinophilic large granules like those of Paneth cells were found in many cancer cells. In addition, argyrophilic cancer cells were seen by Grimelius' stain. Immunoperoxidase staining elucidated a definite reactivity for lysozyme in the granules like Paneth cells. Ultrastructurally, the granules of Paneth cell-like cancer cells were electron-dense spherical bodies with a medium diameter of 540 nm. Prostatic adenocarcinoma with argyrophilia is rare, and the argyrophilic adenocarcinoma with Paneth cell-like granules is very rare in the prostate.