Metastasis Of An Ascending Colon Carcinoma In The Prostate 10 Years After Hemicolectomy

Abstract

Secondary involvement of the prostate by malignant tumors is unusual unless direct invasion occurs. We report on a patient who presented with signs and symptoms of bladder outlet obstruction caused by a prostatic metastasis of an ascending colon carcinoma 10 years after hemicolectomy. CASE REPORT An 80-year-old man was admitted for transurethral prostatectomy because of repeat episodes of acute urinary retention. The patient had a history of partial resection of the ascending colon for adenocarcinoma (TNM pT3, grade 2, N0) 10 years prior to presentation, as well as resection of 2 solitary pulmonary metastases 7 and 5 years earlier. Routine laboratory tests were normal, including prostate specific antigen (1.04 ng./ml.). Only carcinoembryonic antigen was slightly increased (5.72 ng./ml.). Digital rectal examination revealed an increased consistency of the left lobe of the prostate. Colonoscopy, computerized tomography of the chest, abdomen and pelvis, and cerebral magnetic resonance imaging did not show local or distant tumor recurrence. Cystoscopy prior to transurethral prostatectomy demonstrated a normal bladder mucosa and 2 prominent lobes of the prostate. Transurethral prostatectomy was performed and the postoperative course was unremarkable. Histopathological evaluation of the entire surgical specimen revealed areas of benign micronodular prostatic hyperplasia, as well as small foci of a poorly differentiated cribriform and solid adenocarcinoma (fig. 1). The tumor cell cytoplasm was basophilic, and the grade of nuclear atypia and number of mitoses were remarkably high. Immunohistochemically, the tumor cells did not react with antibodies directed against prostate specific antigen or prostatic acid phosphatase. Cytokeratin 7 was also negative. However, the tumor cells stained positive for cytokeratin 20, a marker that is expressed in virtually all cases of colorectal carcinomas but is negative in prostatic carcinoma (fig. 2, a). In addition, carcinoembryonic antigen staining was positive, and p53 protein stabilization was detected in more than 90% of the tumor nuclei, a phenomenon typical for colorectal cancer but uncommon for prostate cancer (fig. 2, b). Therefore, the diagnosis of metastatic colorectal adenocarcinoma of the prostate was established. Because of age, radical prostatectomy was not considered despite the negative further metastatic workup. Instead, the patient was placed on external beam radiation therapy, which was ongoing at the time of this report.