Surreal illustration of colon transforming into a flower, representing endometriosis

Endometrioid Adenocarcinoma: A Rare Twist in Colon Health?

Samir D’Costa in Health & Wellness December 2025 • 4 min read.

"Unveiling a surprising case of colon endometriosis and its malignant transformation in a postmenopausal woman, challenging common perceptions."

Endometriosis, a condition affecting up to 10% of women, typically involves the growth of endometrial tissue outside the uterus. While often associated with pelvic pain and infertility, endometriosis can manifest in unexpected locations. Epidemiologists predict that diagnosed prevalent cases of endometriosis are going to increase in future.

In some instances, endometriosis can affect the intestinal tract, accounting for 3%–37% of all patients with pelvic endometriosis, with the sigmoid colon and rectum being the most commonly involved areas. While rare, malignant transformation of endometriosis can occur, leading to the development of endometriosis-associated intestinal tumors (EAITs).

This article delves into an extraordinary case: a postmenopausal woman who experienced malignant transformation of an endometriotic lesion in the rectosigmoid colon, defying typical risk factors. This case highlights the importance of vigilance and thorough investigation when encountering unusual gastrointestinal symptoms in women.

Decoding the Case: Atypical Presentation of Colon Endometriosis

Surreal illustration of colon transforming into a flower, representing endometriosis

A 75-year-old woman presented with diffuse abdominal pain and enterorrhagia (intestinal bleeding). Her medical history included hypertension treated with an angiotensin II receptor blocker. The patient had no prior complaints of bowel or reproductive system issues, and there was no family history of colorectal or endometrial cancers. The woman had experienced menopause at 55 and reported regular menstrual cycles with no dysmenorrhea (painful periods).

Initial investigations included a colonoscopy, which was incomplete due to bowel intussusception (where one part of the intestine slides into another) 28 cm from the anus. Biopsies taken during the colonoscopy revealed intestinal mucosa with tubular adenoma of low-grade dysplasia (a precancerous condition). A computed tomography (CT) scan of the abdomen revealed a concerning midline pelvic lesion.

CT scans showed a midline pelvic lesion measuring 6.1 cm.
Two additional nodal lesions, each 2.8 cm in diameter, were found nearby.
One of these lesions was in contact with the uterus, suggesting potential local spread.
Small cystic lesions were observed in both ovaries.
Lower abdomen ultrasound showed an atrophic uterus with a thin endometrium.

The patient underwent sigmoidectomy (surgical removal of the affected part of the sigmoid colon). During surgery, the uterus and adnexa (ovaries and fallopian tubes) appeared normal, so no hysterectomy or oophorectomy were performed. Histological examination confirmed a moderately differentiated adenocarcinoma (a type of cancerous tumor) of the colon. Based on the morphology and immunohistochemical analysis, the diagnosis was an endometrioid adenocarcinoma arising from endometriosis. The postoperative period was smooth, and the patient was discharged in good condition.

Key Takeaways: Vigilance and Comprehensive Diagnosis

This unusual case emphasizes the importance of considering endometriosis-associated intestinal tumors (EAITs) in women presenting with gastrointestinal symptoms, even in postmenopausal individuals without typical risk factors. A high level of suspicion, combined with thorough histological and immunohistochemical examination (including CK7, CK20, CDX2, CD10, ER, and PR), is crucial for accurate diagnosis and appropriate management.

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Everything You Need To Know

What is Endometrioid Adenocarcinoma, and how is it related to Endometriosis?

Endometrioid Adenocarcinoma is a type of cancer that can develop from endometriosis. Endometriosis is a condition where tissue similar to the uterine lining (endometrium) grows outside the uterus. In rare cases, this endometrial tissue can undergo a malignant transformation, leading to the development of Endometrioid Adenocarcinoma. This case specifically discusses how Endometrioid Adenocarcinoma arose from an endometriotic lesion in the rectosigmoid colon.

In what parts of the body is Endometriosis most likely to occur, and where was it found in this case?

While Endometriosis can occur in various locations, it is most commonly associated with the pelvic region. It can affect the intestinal tract in about 3%–37% of patients with pelvic endometriosis, with the sigmoid colon and rectum being the most commonly involved areas. In this case, Endometriosis, which subsequently developed into Endometrioid Adenocarcinoma, was found in the rectosigmoid colon of a 75-year-old woman.

What were the initial symptoms and diagnostic steps taken when the 75-year-old woman was examined?

The 75-year-old woman presented with diffuse abdominal pain and enterorrhagia (intestinal bleeding). Initial investigations included an incomplete colonoscopy and a CT scan of the abdomen. The colonoscopy revealed intestinal mucosa with tubular adenoma of low-grade dysplasia. The CT scan showed a midline pelvic lesion, two additional nodal lesions, and small cystic lesions in both ovaries, suggesting a potential spread.

Why is it important to consider Endometriosis-associated intestinal tumors (EAITs) in women with gastrointestinal symptoms, even in postmenopausal individuals?

It is important to consider Endometriosis-associated intestinal tumors (EAITs) in women with gastrointestinal symptoms because these tumors can arise from endometriosis, even in the absence of typical risk factors. The case presented involves a postmenopausal woman, challenging the common perception that such conditions are limited to women of reproductive age. This highlights the need for vigilance and thorough investigation, including histological and immunohistochemical examinations, for accurate diagnosis and appropriate management.

What diagnostic tools and procedures are crucial for diagnosing Endometrioid Adenocarcinoma arising from Endometriosis?

Accurate diagnosis of Endometrioid Adenocarcinoma arising from Endometriosis requires a high level of suspicion combined with comprehensive diagnostic tools. These include a thorough histological and immunohistochemical examination. The immunohistochemical analysis should include markers like CK7, CK20, CDX2, CD10, ER, and PR. These tools help to confirm the diagnosis and differentiate the cancerous cells, ensuring the correct course of treatment and management of the patient.