Pathologic quiz case. A colonic mass in a 53-year-old woman

Pathologic Quiz Case: A Colonic Mass in a 53-Year-Old Woman A 53-year-old postmenopausal woman presented with a several month history of nonbloody diarrhea and left lower quadrant pain. The patient's past medical history and surgical history were significant for hypertension, fibrocystic breast changes, polycystic kidney disease, a total abdominal hysterectomy and salpingo-oophorectomy for endometriosis 16 years earlier, and a laparoscopic cholecystectomy performed 3 years earlier. The patient had been undergoing hormone replacement therapy, consisting of 0.625 mg/d of conjugated estrogens, for more than 5 years before presentation. Her physical examination findings were essentially unremarkable, including negative digital rectal examination results and hemoccult stool test results. Complete blood cell data showed a hematocrit of 31.9% and a mean corpuscular volume of 91.3 fL. The patient underwent a diagnostic workup that included a colonoscopy and computed tomographic (CT) scan. The colonoscopy showed acute angulation of the colon at 25 cm consistent with a mural or extrinsic process; however, there was no visualization of a mass. “Blind” biopsy specimens were taken that showed benign colonic mucosa with focal hyperplastic features. A CT scan of the abdomen and pelvis revealed a 2.8 × 1.6-cm soft tissue mass in the rectosigmoid area with no free air or lymphadenopathy. A carcinoembryonic antigen level of 1.1 ng/mL (range, 0–5.0 ng/mL) was obtained. The patient underwent surgery, and intraoperative findings showed a fibrotic mural rectosigmoid colonic mass. A sigmoid colectomy was performed without difficulty. The patient had an uneventful recovery, and the patient's symptoms resolved. When the fixed colectomy specimen was opened, a 2.0-cm exophytic mass projected from the mucosal surface. The lesion was composed of yellow-to-pink tissue with numerous small polypoid projections with no obvious hemorrhage, necrosis, or ulceration. Sections through the mass revealed dense, white, transmural fibrosis of the colonic wall and puckering of the pericolonic fat (Figure 1). Microscopic examination showed a polypoid lesion composed of tubular glands with hypercellular stroma replacing the colonic mucosa (Figures 2 and 3). Similar glands were present throughout the submucosa and muscularis propria with surrounding stromal cells (Figure 3). Immunohistochemical staining with CD10 showed diffuse staining of the surrounding stroma with glandular sparing (Figure 4). What is your diagnosis? Pathologic Diagnosis: Intestinal Endometriosis This case illustrates the unusual presentation of a postmenopausal woman who had symptomatic colonic endometriosis with transmural involvement despite a hysterectomy and bilateral salpingo-oophorectomy 16 years previously. Endometriosis is defined as the abnormal growth and function of ectopic endometrial tissue at an extrauterine site. Rokitansky first reported endometriosis of the large bowel in 1860. Meyer, in 1909, described an endometrioma that resulted in intestinal obstruction.1 The incidence of bowel endometriosis is quoted to be anywhere from 3% to 34% in patients with known preexisting endometriosis.1,2 The most commonly involved gastrointestinal areas are, in decreasing order, the rectosigmoid and sigmoid colon (75%), the appendix (3%–18%), and the distal ileum (2%–16%).3 Colonic endometriosis normally afflicts women of menstruating age because regression usually occurs following surgical castration or natural menopause. A number of articles have been written documenting postmenopausal cases; however, it is seldom considered in the differential diagnosis. Henriksen described 37 cases among postmenopausal women following 2 years of amenorrhea; 6 of these 37 patients underwent large resections of the bowel for suspected neoplasm. He further stated that the diagnosis of endometriosis was not considered in any of these cases.4 The primary symptom of abdominal pain and/or accompanying rectal bleeding, often accompanied by diarrhea or constipation, tenesmus, change in caliber of stool, and abdominal distention, raises the possibility of carcinoma. In a case series by Rose, a single patient was undergoing estrogen hormone replacement therapy 8 months after a total abdominal hysterectomy and salpingo-oophorectomy for endometriosis. Three years following this surgery, she presented with continued bouts of lower abdominal pain, distention, and bloody stools. At laparotomy, she was found to have a 3-cm cecal endometrioma.5 It should be stressed that our patient and the patient in Rose's case series were both receiving estrogen hormone replacement therapy for a period following surgical castration. Therefore, the continued estrogen hormone replacement therapy may exacerbate mucosal endometrial lesions. Colonic endometriosis can mimic a variety of colorectal disorders radiologically and microscopically, including colorectal carcinoma. It is generally confined to the submucosa, muscularis, and serosal layers, making endoscopic diagnosis difficult. The incidence of endometriosis with mucosal involvement, as illustrated in this case, appears to be rare.2,5–7 Even when the mucosa is involved, as in the present case, accurate diagnosis of minute colonic biopsy specimens may prove difficult because endometrial glands may resemble colonic glands and endometrial stromal cells may not be easily recognized.8 Recently, CD10 (CALLA) expression in normal endometrial stroma has been found to aid in identifying areas of endometriosis, especially when there is a paucity of glandular elements and/or when there is a background of chronic, active inflammation.9 The present case highlights this well with marked endometrial stromal staining with CD10. Furthermore, the pathologist must be aware of mucosal changes that may mimic other gastrointestinal conditions, including inflammatory bowel disease, colitis, or solitary rectal ulcer.6–8 Surgery still remains the standard of treatment for obstructive symptoms. First, tissue for accurate histopathologic diagnosis is often not obtainable without surgery, a point highlighted in our case. Second, endometrial glands that are deep to the mucosa often cause a severe inflammatory response, leading to fibrosis of the bowel wall. The fibrosis can lead to irreversible stenosis and obstruction because these lesions do not appear to respond to hormonal manipulation.2,5 Finally, there is a small incidence of malignant transformation within or near the site of endometriosis.2 The frequency of malignant transformation is estimated to be up to 1%, with endometrial carcinoma being the most prevalent pathologic type (40%).10 There is an association with unopposed estrogen stimulation and malignant transformation to generally a low-grade neoplasm with an 83% survival rate. The addition of progesterones may prevent this iatrogenic complication.10