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Session: ePoster: Colon and Colorectal Cancer 2 (Sun1230)

EP419 - High-grade serous carcinoma of Müllerian origin masquerading as colorectal cancer

Sunday, May 11, 2025
12:51 PM – 12:56 PM PT
Location: Monitor 3, Sails Pavilion, Upper Level

    ePoster Presenter(s)

  • Yuen-Joyce Liu, MD

    Resident
    University of Connecticut

    All of the relevant financial relationships listed below have been mitigated.
    This individual has no financial relationships with ineligible companies.

    • Author(s)

  • JC

    Jonathan Chang, MD

    Clinical Fellow
    St. Francis Medical Center and Hospital
    Farmington, Connecticut, United States

    Disclosure information not submitted.

    • Senior Author(s)

  • RS

    Rachel B. Scott, DO, DO

    Chief of Colon and Rectal Surgery St. Francis Hospital
    Colon and Rectal Surgeons of Greater Hartford
    Willington, Connecticut, United States

    All of the relevant financial relationships listed below have been mitigated.
    This individual has no financial relationships with ineligible companies.

All of the relevant financial relationships listed below have been mitigated.
Yuen-Joyce Liu, MD: This individual has no financial relationships with ineligible companies.
Rachel B. Scott, DO, DO: This individual has no financial relationships with ineligible companies.
Image or Table (Do Not add text here):

Purpose/Background: High-grade serous carcinoma (HGSC) is a tumor arising from the serous epithelium of the abdominopelvic cavity, most often from the ovary. HGSCs of Müllerian origin that involve the colon and rectum are rare and challenging to diagnose, particularly in individuals who have no history of gynecologic malignancies. In this report, we consider a patient with a history of diabetes mellitus who presented with clinical signs and endoscopic findings suggestive of a primary colorectal cancer, discovered to be an unusual case of HGSC of Müllerian origin on pathology.

Methods/Interventions: N/A

Results/Outcomes: A 43 year-old female with a history of diabetes mellitus but no personal or family history of colorectal cancer or inflammatory bowel disease (IBD) presented to the clinic with new onset anal stenosis and painful bowel movements. Computed tomography (CT) of the abdomen and pelvis revealed extensive rectal wall thickening with adjacent adenopathy. There were omental opacities and nodules suspicious for carcinomatosis, concerning for metastatic colorectal cancer. An exam under anesthesia revealed a circumferential, infiltrating, malignant mass involving the anal verge and extending 10 cm proximally into the distal rectum, which could not be traversed with a flexible colonoscope. Biopsy of the rectal mass revealed a high-grade, poorly differentiated carcinoma involving the colonic submucosa with no intramucosal carcinoma or high-grade dysplasia. Immunostains were positive for CK7, PAX8, WT1, p16, and p53 and negative for markers of gastrointestinal origin (CDX2, SATB2, CK20), TTF-1, neuroendocrine markers (INSM1, chromogranin, synaptophysin), p40, GATA3, and ERG. The immunophenotype of this high-grade carcinoma supported a Müllerian origin with a p53 mutation compatible with serous carcinoma. The patient was diagnosed with stage IVB HGSC of Müllerian origin, suspected to be primary peritoneal, and subsequently underwent neoadjuvant chemotherapy followed by exploratory laparotomy, debulking, total abdominal hysterectomy (TAH), bilateral salpingo-oophorectomy (BSO), and abdominoperineal resection (APR) with ostomy creation. Her post-operative course was complicated by hyperglycemia, tachycardia, ileus, as well as perineal wound dehiscence secondary to a draining abscess that resolved with antibiotics and non-operative management.

Conclusion/Discussion: We present a rare case of HGSC of Müllerian origin that masqueraded as a primary colorectal cancer. HGSC is an aggressive tumor and, as in this patient, is often diagnosed in advanced stages. This report highlights the importance of obtaining accurate biopsies, morphologic evaluation, and appropriate immunohistochemical stains for correct diagnosis and subsequent management.