Ectopic Prostatic Tissue Involving The Omentum And Presenting With Intussusception And Small Intestinal Obstruction: A Report Of A Rare Case With A Review Of The Literature

ABSTRACT

Ectopic prostatic tissue has been uncommonly reported within the literature in the past, typically described involving areas within the lower genitourinary tract. Although patients can occasionally present with urinary symptoms related to the ectopic prostatic tissue, many of these cases are identified incidentally. Ectopic prostatic tissue, depending on the location, can represent a diagnostic dilemma for both clinicians and pathologists and generate a broad differential diagnosis that includes non-neoplastic and neoplastic proliferations, including both benign and malignant neoplasms.

Here we report a case of an 85-year-old male who presented with nausea, vomiting, and abdominal pain and was found to have an omental mass causing a distal small intestinal obstruction on pre-operative radiologic imaging, confirmed on exploratory laparotomy. A metastatic carcinoma was suspected clinically, as the patient had a known cystic lesion diffusely involving the pancreas. However, gross and histological evaluation of the specimen revealed an omental mass adherent to the small intestinal serosa that showed central infarction and features diagnostic of ectopic prostatic tissue, confirmed with immunohistochemical stains

KEYWORDS: Ectopic prostatic tissue Omental mass Small intestinal obstruction Intussusception Case report.

Introduction

Ectopic prostatic tissue is an uncommon and often incidental histological observation, with less than 100 cases having been reported in the literature. When present, ectopic prostatic tissue is most commonly seen in the lower genitourinary tract, particularly within the urinary bladder ^[1–4] and urethra ^[5,6]. Very rarely, ectopic prostatic tissue has also been described in other sites within the lower pelvic region ^[7–9]. For these cases in particular, this unexpected microscopic finding can pose a significant diagnostic dilemma, especially when a malignancy is clinically anticipated. We report an unusual and clinically unsuspected case of ectopic prostatic tissue within the omentum adherent to the small intestine with secondary intussusception and intestinal obstruction.

Case Report

An 85-year-old male presented to the hospital with a 4–5-day history of generalized abdominal pain along with nausea and vomiting. His past medical and surgical history was significant for a cholecystectomy approximately 60 years ago, a right inguinal hernia repair 4 years prior and benign prostatic hyperplasia, status-post transurethral resection of the prostate, also 4 years ago. At the time of his prior surgical procedures, an incidental pancreatic mass was identified on an abdominal CT scan, determined to be hypermetabolic on a follow-up PET scan, though no further diagnostic work-up was reportedly done at the time. On initial examination within the emergency department his abdomen was soft, nondistended, nontender, and notable for a 10 cm scar from his prior cholecystectomy. A CT of the abdomen and pelvis with contrast was performed which showed evidence of a small intestinal obstruction characterized by dilation of the duodenum and jejunum over 5 cm, with a transition to nondistended ileum in the anterior left pelvis. This transition occurred adjacent to a 25 mm soft tissue nodule with associated calcifications (Fig. 1). This soft tissue nodule was 16 cm superior and left-lateral to the dome of the urinary bladder. Also appreciated on this imaging study were numerous cystic densities within the pancreas involving the head, body, and tail, measuring up to 3.7 cm in greatest dimension, with associated mild dilation of the main pancreatic duct. These latter findings were interpreted as possibly representing an intraductal papillary mucinous neoplasm (IPMN) of the pancreas, branch duct type. Based on these findings and the patient’s presentation, the working diagnosis was that of a small bowel obstruction secondary to an adjacent soft tissue mass, possibly representing a metastasis from his pancreatic lesion. Therefore, he was decompressed with a nasogastric (NG) tube and taken to surgery for a small intestinal resection, to encompass the adjacent soft tissue mass. At the time of the exploratory laparotomy, a proximal dilation of the small intestine was identified extending to the distal jejunum/proximal ileum with a high-grade obstruction noted at the point of a serosal adhesion to an omental mass in the left lower quadrant of the abdomen. Therefore, a segmental resection of the distal small intestine was performed to include the adjacent adherent omental mass.

At the time of gross evaluation in pathology, a 20.0 cm in length portion of small intestine was identified with associated adherent omental adipose tissue, forming a convoluted structure measuring 8.9 × 6.5 × 3.4 cm. Upon sectioning, an area of intussusception was noted within the resected small intestine. External to this focus and within the omental adipose tissue, an adjacent 2.5 × 2.3 × 2.2 cm well circumscribed mass was identified with a tan-yellow, firm-to-rubbery, and greasy cut surface (Fig. 2). No mucosal abnormality was appreciated within the adjacent portion of intestine.

Microscopic evaluation of the mass revealed a well-circumscribed, though unencapsulated, mass within the omental adipose tissue composed of lobulated glands separated by hypocellular and fibrous stroma without evidence of desmoplasia (Fig. 3a and b). This mass was not attached to the small intestinal wall and the adjacent mucosa appeared unremarkable. The viable epithelial and stromal elements within the lesion were predominantly noted at the periphery of the mass, with large areas of central infarct-type necrosis associated with scattered dystrophic calcifications. The individual glands were lined by a layer of luminal epithelial cells with basally located nuclei and varying amounts of cytoplasm, ranging from voluminous and vacuolated within some of the more tufted epithelial structures (Fig. 3c) to scant within flattened cells lining the glands possessing a microcystic appearance (Fig. 3d). In addition to the luminal epithelial cells, the glands also appeared to have a second, outer layer of cells. No significant nuclear atypia or mitotic activity was appreciated, and no prominent inflammatory infiltrate was identified.

Immunohistochemical analysis of the mass revealed that the glands stained diffusely and strongly for NXK3.1 and PSA (Fig. 4a and b) within the luminal epithelial cells. A cytokeratin AE1/AE3 was also strongly positive within the glands. A p63 stain highlighted an outer basal layer associated with all of the glands (Fig. 4c). GATA3 also showed patchy and strong positivity within some of the glands (Fig. 4d). The cells were negative for CK7, CK20, calretinin, CDX2, PAX8 and SATB2.

In combination with the morphological and immunophenotypic features, a diagnosis of ectopic prostatic tissue involving the omentum with associated small intestinal intussusception was made...

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Paul J. Michaels, MD, is a nationally renowned Anatomical and Clinical Pathologist with over 20 years of experience in his field. Dr. Michaels completed his medical residency and earned a Fellowship in Cytopathology from Massachusetts General Hospital / Harvard Medical School. He offers expert witness services to attorneys representing plaintiff and defense. He has written over 100 general causation reports focusing on pathology and providing an extensive differential diagnosis in order to provide an opinion with a reasonable degree of medical certainty. Dr. Michaels has participated in numerous MDLs, been deposed over 60 times, and testified in court 6 times.

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