University of Texas Health Science Center
San Antonio, TX
Colorectal cancer (CRC) is the 5th most common cancer in the US. Symptomatic patients typically present with hematochezia, abdominal pain, constipation and/or weight loss and are usually diagnosed on colonoscopy. We present a case of fistulizing CRC following an unusual presentation and diagnostic sequence, with an initial report of feculent vaginal discharge prompting a pelvic exam and resulting in a cytologic diagnosis of adenocarcinoma on Pap smear.
A 44-year-old obese woman presented to her PCP with 2-3 months of worsening lower abdominal and rectal pain along with feculent vaginal discharge. She denied a family history of colorectal, ovarian, or breast cancer. Physical exam elicited tenderness in the suprapubic region and left lower quadrant with a palpable midline mass. A black tinged discharge and a hard fixated mass palpated along the vaginal walls was discovered on pelvic exam. A Pap smear returned positive for mucinous adenocarcinoma. Further workup revealed iron deficiency anemia and an elevated CEA (24.6). Subsequent CT showed circumferential rectal wall thickening with anterior extension to the vagina and bilateral pelvic sidewall, pelvic adenopathy and a possible rectovaginal fistula, as well as bilateral cystic adnexal masses likely representing metastases (Figure 1). Colonoscopy uncovered a large circumferential rectal friable mass (Figure 2), as well as 17 polyps throughout the colon (Figure 3). Biopsies confirmed the diagnosis of poorly differentiated invasive adenocarcinoma as well as a mixture of adenomatous and inflammatory polyps. Testing for microsatellite instability was negative.
To the best of our knowledge, only one other case of a de novo diagnosis of advanced CRC by an abnormal pap smear has been reported. Our case highlights the rare potential of CRC to present with fistulization to the vagina. In an analogous fashion, CRC can present with fecaluria from a colovesical fistula or stercoraceous vomiting from a gastrocolic fistula. In contrast to our patient, most rectovaginal fistulas are related to benign conditions such as prior trauma, surgeries, infections and inflammatory bowel disease. Our patient was also significantly younger than the average age of diagnosis of metastatic colon cancer, following the recent trends of rising diagnosis of metastatic colon cancers in patients younger than 50. Given her youth and the abundance of additional adenomas, we plan to pursue genetic testing.
Image 1. Irregular thickening from the upper rectum to anal verge with suspected vaginal invasion and rectovaginal fistula.
Image 2. Rectal mass spanning from the anal verge to 15cm proximally
Image 3. Multiple polyps throughout the colon, ranging from 3-7mm in size.
James Gnecco indicated no relevant financial relationships.
Brenda Briones indicated no relevant financial relationships.
Jacqueline Rampy indicated no relevant financial relationships.
Patrick Snyder indicated no relevant financial relationships.