Secondary Colonic Adenocarcinoma of the Prostate Histologically Mimicking Prostatic Ductal Adenocarcinoma

Imaging of non-epithelial neoplasms of the prostate

The purpose of this article is to review the spectrum of rare non-epithelial tumors of the prostate. This focused article will help the readers to understand the imaging findings of such rare entities attributed to their clinicopathological features. Radiologists must be familiar with the spectrum of non-epithelial tumors of the prostate, which helps to suggest alternate diagnosis other than adenocarcinoma, when imaging features are atypical. This is important because these tumors have different management approaches and prognoses when compared to adenocarcinoma of the prostate.

Mucinous and secondary tumors of the prostate

Primary mucinous tumors and secondary tumors involving the prostate gland are relatively uncommon, however they have important diagnostic, therapeutic, and prognostic implications. The primary mucinous tumors of the prostate include mucinous (colloid) adenocarcinoma of the prostate, prostatic adenocarcinoma with mucinous features, and mucinous adenocarcinoma of the prostatic urethra (mucin-producing urothelial-type adenocarcinoma of the prostate). Mucinous adenocarcinoma of the prostate is defined as a primary prostatic acinar tumor characterized by the presence of at least 25% of the tumor composed of glands with extraluminal mucin. This diagnosis can only be made in radical prostatectomy specimens. Recent studies have shown that these tumors have a similar or in some cases better prognosis than conventional prostatic adenocarcinoma treated by radical prostatectomy. The preferred terminology for tumors that are composed of <25% extraluminal mucinous component in radical prostatectomy specimens is 'prostatic adenocarcinoma with mucinous features.' All cases of prostatic adenocarcinoma with extraluminal mucinous components in prostate needle core biopsies or transurethral resection of the prostate specimens are also referred to as 'prostatic adenocarcinoma with mucinous features.' Mucinous adenocarcinoma of the prostatic urethra (mucin-producing urothelial-type adenocarcinoma of the prostate) as the name implies, does not arise from prostatic acini or ducts, and is a distinct entity that arises from the prostatic urethra usually from urethritis glandularis or glandular metaplasia with malignant transformation, and is analogous to adenocarcinoma with mucinous differentiation arising from the urinary bladder. This tumor is aggressive and has a relatively poor prognosis. The most common secondary tumors that arise from adjacent organs and spread (direct extension or metastasis) to the prostate gland, include urothelial carcinoma of the bladder and colorectal adenocarcinoma. Other secondary tumors that may involve the prostate include metastatic epithelial tumors from several other sites, malignant melanoma and soft tissue tumors.

Mucin-producing tumors and tumor-like lesions involving the prostate: a comprehensive review

Mucin-producing tumors of the prostate include both primary and secondary tumors with mucinous differentiation or features involving the prostate gland. These tumors are relatively rare and have variable prognostic and therapeutic implications. Primary mucinous (colloid) adenocarcinoma of the prostate is defined as prostatic adenocarcinoma with mucinous differentiation involving 25% or more of the entire tumor. Another primary tumor of the prostate that may have mucinous features is primary mucin-producing urothelial-type adenocarcinoma of the prostate (mucinous prostatic urethral adenocarcinoma). Primary mucin-producing urothelial-type adenocarcinoma of the prostate is a distinct entity that typically arises from the prostatic urethra possibly from urethritis glandularis or glandular metaplasia with malignant transformation, and it is analogous to adenocarcinoma with mucinous differentiation arising from the urinary bladder. Signet ring cell tumors of the prostate, though rare, may also have mucinous features. Secondary tumors with mucinous differentiation that may involve the prostate include adenocarcinomas of the urinary bladder and colorectum. Pathologists should also be aware of mucin-producing tumor-like lesions involving the prostate, including mucinous metaplasia, and benign Cowper glands that may mimic malignancy. Herein we present an updated and comprehensive review of the clinicopathologic, immunohistochemical, molecular, and prognostic features of mucinous tumors and tumor-like lesions involving the prostate gland, with emphasis on mucinous prostatic adenocarcinoma and its mimickers, including potential diagnostic pitfalls.

Colorectal adenocarcinoma involving the prostate: report of 9 cases

We present 9 consult cases, the largest series to date, of colorectal adenocarcinoma involving the prostate. Mean age of patients at diagnosis was 61 years (range, 42-78 years). Six cases were initially diagnosed on needle biopsy and the others by transurethral resection. Three cases were diagnosed before biopsy of the colon, which led to the discovery of a primary colonic tumor. The mean interval between the detection of the primary colonic tumor and prostatic involvement in the other 6 cases was 30 months (range, 1-52 months). At diagnosis, the stages of colorectal carcinomas were pT1 (n=2), pT2 (n=2), pT3 (n=2), and pT4 (n=3). Two cases involved the prostate after the recurrence of rectal adenocarcinoma at the anastomotic site of the previous colonic resection. In most cases, the tumors were typical moderately differentiated with occasional poorly differentiated foci. Other histologic features included desmoplastic stromal reaction (100%, n=9), necrosis (77.8%, n=7), chronic inflammatory response (77.8%, n=7), cribriform pattern (66.7%, n=6), villous architecture (22.2%, n=2), mucin production (22.2%, n=2), signet-ring cells (11.1%, n=1), and perineural invasion (11.1%, n=1). Immunohistochemical stains were positive for beta-catenin in 6 of 6 cases, CDX2 in 6 of 6 cases, carcinoembryonic antigen in 7 of 7 cases, CK20 in 5 of 6 cases, high-molecular-weight cytokeratin in 5 of 6 cases, and alpha-methylacyl-CoA racemase in 3 of 6 cases. Stains were negative in all cases for prostate-specific antigen, P501S (prostein), and CK7. Six patients (66.7%) died of disease within an average of 34 months (range, 8-88 months) after diagnosis of prostatic involvement. There are critical therapeutic and prognostic implications for distinguishing between prostatic adenocarcinoma and colorectal carcinoma involving the prostate. Colorectal adenocarcinoma should be considered on prostate sampling when carcinoma exhibits either "dirty" necrosis, tall columnar epithelium with mucin production, mucin-positive signet-ring cells, villous architecture, or associated inflammation. Immunohistochemical stains for beta-catenin, CDX2, carcinoembryonic antigen, high-molecular-weight cytokeratin, prostate-specific antigen, P501S (prostein), CK20, and CK7 can be helpful in making a definitive diagnosis.

Primary mucin-producing urothelial-type adenocarcinoma of prostate: report of 15 cases

Prostatic urothelial-type adenocarcinoma arises through a process of glandular metaplasia of the prostatic urethral urothelium and subsequent in situ adenocarcinoma sometimes associated with villous adenoma. These prostatic adenocarcinomas are analogous to nonurachal adenocarcinomas arising in the bladder from cystitis glandularis. Only 2 cases of urothelial-type adenocarcinoma from an institution other than our own have been previously described. The distinction between adenocarcinoma from another organ secondarily involving the prostate, usual adenocarcinoma of the prostate, and prostatic urothelial-type adenocarcinoma can present a significant diagnostic challenge and has significant therapeutic implications. Fifteen cases of prostatic urothelial-type adenocarcinoma were retrieved from the consult files of one of the authors. Mean patient age at diagnosis was 72 years (range 58 to 93 y). All men had negative colonoscopies, clinically excluding a colonic primary. Bladder primaries were ruled out clinically or pathologically in radical resection specimens. Follow-up was available on all men with a mean of 50.3 months (range 2 to 161 mo). All men presented with urinary obstruction symptoms with 3 (20%) also having mucusuria and 2 (13.3%) also having hematuria. Four men (26.7%) developed metastatic disease and 8 (53.3%) died of disease. In 8/15 (53%) cases, glandular metaplasia of the prostatic urethra and contiguous transition to adenocarcinoma were identified. Multiple histologic patterns were observed including dissection of the stroma by mucin pools 15/15 (100%), villous features 7/15 (47%), necrosis 2/15 (13.3%), signet ring cells 3/15 (20%), perineural invasion 1/15 (6.7%), focal squamous differentiation 1/15 (6.7%), and a granulomatous inflammatory response 1/15 (6.7%). Immunohistochemical stains were negative for prostate specific antigen, prostate specific acid phosphatase, CDX2, and beta-catenin in all cases. Stains were positive for high molecular weight cytokeratin in 12/12 cases (100%), and CK7 and CK20 in 10/12 cases (83.3%). Prostatic urothelial-type adenocarcinoma is a rare aggressive cancer arising in the prostate. The differential diagnosis includes conventional prostatic mucinous adenocarcinoma and secondary infiltration from a colonic or bladder adenocarcinoma. Immunohistochemistry for prostate specific antigen, prostate specific acid phosphatase, and high molecular weight cytokeratin along with morphology can help rule out conventional prostate carcinoma. beta-catenin, CDX2, and clinical studies are needed to rule out colonic adenocarcinoma. As prostatic urothelial-type adenocarcinoma is entirely analogous to bladder adenocarcinoma in both, its morphology and immunophenotype, only clinical studies or in some cases pathologic examination of the cystoprostatectomy specimen can exclude infiltration from a primary bladder adenocarcinoma.

Distinguishing prostatic from colorectal adenocarcinoma on biopsy samples: the role of morphology and immunohistochemistry

CONTEXT

Poorly differentiated carcinoma on prostate or colorectal biopsy can occasionally present a diagnostic challenge in determining tumor source especially in locally advanced colorectal carcinoma (CRCa) or prostate carcinoma (PCa). Such determination can affect prognosis and therapy.

OBJECTIVE

To evaluate the role of morphology and immunohistochemistry in the previously mentioned setting.

DESIGN

Surgical pathology and consultation records. Hematoxylin-eosin sections were reviewed in 16 cases (11 PCa, 5 CRCa). Immunohistochemistry for 9 markers was performed in 15 cases.

RESULTS

Dirty necrosis, seen in 5 (100%) of 5 CRCa and 2 (18%) of 11 PCa cases, and the presence of columnar cells with basal nuclei, seen in 5 (100%) of 5 CRCa and 1 (9%) of 11 PCa cases, appear to be the most useful morphologic parameters. Immunohistochemistry confirmed the value of prostate-specific antigen (PSA), CDX2, cytokeratin (CK) 20, and beta-catenin in the differential of CRCa (0% PSA+, 60% CDX2+, 80% CK20+, and 100% beta-catenin+) versus PCa (80% PSA+, 0% CDX2+, 10% CK20+, and 0% beta-catenin+). P501S had a similar sensitivity as PSA in detecting PCa (80%). Two (20%) of 10 PCa cases were positive for 1 of the 2 markers but not the other. P501S was negative in all 5 cases of CRCa.

CONCLUSIONS

P501S is a useful marker in this setting when included together with PSA, CDX2, CK20, and beta-catenin. P501S labels a subset of PCa cases that are negative for PSA. Dirty necrosis and/or columnar cells with basal nuclei could also be of help.