Intraluminal crystalline structures having distinctive morphological characteristics were noted by Holmes1 in 1977 in association with prostatic adenocarcinoma. In her series of 335 cases, she found these crystalloids in 23%. The structures were almost exclusively confined to malignant glands and were not seen in benign prostates. A study by Jensen et al2 and a subsequent study by Ro et al3 found crystalloids in approximately 10% of cases of prostate cancer, suggesting that Holmes' 23% was an overestimation. These differences, however, are probably related to sampling, since recent investigations using whole-organ tissue sections revealed crystalloids in the majority of cases of prostatic adenocarcinoma.4 Although most commonly seen in well-differentiated neoplasms, prostatic crystalloids have been noted in metastatic sites.5 They have also been found in fine-needle aspirates of the prostate (G. F. Worsham, MD, B. W. Kellough, MD; B. S. Collins, MD, unpublished data, 1987).