A Perianal Mass in a Crohn's Disease Patient


Question: A 41-year-old man with long-standing luminal colonic and perianal Crohn’s disease presented with persistent perianal symptoms, pain, indurated gluteus, and active drainage from an external fistula opening. He had been treated with azathioprine and infliximab for the past 5 months. Physical examination showed active draining of pus from fistulae openings in the gluteus and posterior perianal regions. A heterogeneous, protruding mass with ulcerative surface was also found in the perianal region (Figure A). Initial laboratory tests showed no significant changes. Patient underwent a colonoscopy, pelvic magnetic resonance imaging (MRI), and a biopsy of the suspicious mass at physical examination.

What is the most likely diagnosis for this patient?

Answer to the Clinical Challenges and Images in GI Question: Mucinous Adenocarcinoma

Colonoscopy (Figure B) showed a fistulous pore in the anus and an extrinsic protrusion with a normal rectal mucosa. MRI (Figure C) showed a 10 x 4-cm, necrotic, heterogeneous mass in the right ischiorectal region, included in the fistulous tract, which continued to the gluteal surface. Radiologic differential diagnosis between abscess and fistula-related neoplasm was proposed. Pathologic analysis (Figure D) of a biopsy from the perianal mass revealed atypical glands and a mucinous component, leading to diagnosis of a mucinous adenocarcinoma. Subsequent computed tomography showed no metastatic involvement.

Cancer degeneration from a fistulous tract in Crohn's disease is uncommon. Only 61 cases have been reported in the English literature in the past 60 years. On initial physical examination, cancer was only suspected in a small proportion of patients (20%). Adenocarcinoma was the most common type (59%), followed by squamous cell carcinoma (31%). In most patients (59%), fistula originated in the rectum.

Diagnosis is difficult because of the lack of specificity of symptoms and signs and is often delayed, resulting in a poor prognosis. Modern imaging methods, such as MRI, may be very helpful for detecting this severe condition.

Clinicians should have a high suspicion index for this potential complication, especially if fistulous drainage persists and remains refractory to medical therapy. In case of doubt, repeated biopsies should be performed to rule out malignancy.

Uncited References

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  1. Thomas M, Bienkowski R, Vandermeer TJ, et al. Malignant transformation in perianal fistulas of Crohn’s disease: a systematic review of literature. J Gastrointest Surg 2010;14:66 –73.
  2. Freeman HJ, Perry T, Webber DL, et al. Mucinous carcinoma in Crohn’s disease originating in a fistulous tract. World J Gastrointest Oncol 2010;2:307–310.
  3. Devroe H, Coene L, Mortelmans LJ, et al. Colloid carcinoma arising in an anorectal fistula in Crohn’s disease: a case report. Acta Chir Belg 2005;105:110 –111.

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