title: Clinicopathological study of 9 cases of prostate cancer involving the rectal wall.
abstract: BACKGROUND
  Prostate cancer involving the rectal wall is rare and may lead to diagnostic pitfalls.
  
  
  METHODS
  Out of 9504 patients with rectal tumors between January 2003 and January 2015, 9 patients (elderly with a mean age of 74 years) with prostate cancer involving the rectal wall were clinically misdiagnosed with rectal cancer. The lesions were located in the rectum, and included 3 circumferential rectal masses, 1 ulceration lesion, 1 crater-like mass, and 4 protruding lesions. Specimens were acquired using biopsy, fine needle aspiration, or resection. The initial symptoms of these patients included rectal urgency, bowel obstruction, and lower gastrointestinal bleeding. Prostate-related symptoms were not obvious. Histologically, 2 cases showed cancer cell invasion in the mucosa, 1 showed transmural invasion from the mucosa to subserosal soft tissues, and 7 cases had submucosa and muscularis propria involvement. All the 9 cases had muscularis propria involvement. However, there were no intraepithelial neoplasias in the mucosal layer, which is reminiscent of rectal carcinoma. The tumors consisted of small-sized or foamy cells that formed acinus-like, duct-like, and cribriform-like structures. We conducted histological staining and an immunohistochemical analysis for CDX-2, prostate-specific antigen (PSA), P504s, villin, carcinoembryonic antigen, CK-pan, cytokeratin 20, and Ki-67. All tumors were PSA and CK-pan positive, 5 of 9 tumors were P504s-positive, and all tumors were negative for the other markers. All patients underwent standard therapy for prostate cancer after the definitive pathological diagnosis. As of March 31, 2015, 8 patients were alive and 1 had died of prostate cancer 6 months posttreatment.
  
  
  CONCLUSIONS
  Adenocarcinoma appearing in the rectal wall is not always rectal carcinoma. It is necessary to perform a differential diagnosis for prostate cancer in cases of rectal malignant tumors in elderly male patients. Any treatment should be postponed until the final definitive diagnosis is reached.
authors.affiliation: Department of Pathology, Tianjin Union Medical Center, Jieyuan Road, Hongqiao District, Tianjin, 300121, People's Republic of China.
authors.forename: Tao
authors.initials: T
authors.lastname: Tang
authors.affiliation: Department of Pathology, Tianjin Union Medical Center, Jieyuan Road, Hongqiao District, Tianjin, 300121, People's Republic of China.
authors.forename: Zhengduo
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Pathology, Tianjin Union Medical Center, Jieyuan Road, Hongqiao District, Tianjin, 300121, People's Republic of China.
authors.forename: Dan
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Tianjin Union Medical Center, Jieyuan Road, Hongqiao District, Tianjin, 300121, People's Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Qu
authors.affiliation: Department of Pathology, Tianjin Union Medical Center, Jieyuan Road, Hongqiao District, Tianjin, 300121, People's Republic of China.
authors.forename: Guang
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Pathology, Tianjin Union Medical Center, Jieyuan Road, Hongqiao District, Tianjin, 300121, People's Republic of China. zhangshiwu666@aliyun.com.
authors.forename: Shiwu
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis* / Q000473:pathology; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000473:pathology; D012004:Rectal Neoplasms / Q000175:diagnosis*; D012007:Rectum / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor