Published online Nov 6, 2020. doi: 10.12998/wjcc.v8.i21.5159
Peer-review started: July 6, 2020
First decision: August 8, 2020
Revised: August 18, 2020
Accepted: September 17, 2020
Article in press: September 17, 2020
Published online: November 6, 2020
Processing time: 109 Days and 17.2 Hours
Magnetic resonance imaging (MRI) is the standard investigation for suspected perianal diseases. This is important to early diagnose carcinoma arising from anal fistula, even if the incidence is low.
To describe and summarize the MRI findings of carcinoma arising from anal fistula.
To summarize the MRI manifestations of carcinoma arising from anal fistula to help improve the ability to diagnose this entity.
A retrospective study was performed on ten patients diagnosed with carcinoma arising from anal fistula and confirmed by pathological diagnosis between June 2006 and August 2018. All patients underwent preoperative pelvic MRI. Five patients underwent enhanced MRI scans. Rosser’s criteria were used for diagnosing carcinoma arising from anal fistula. Morphologic features, signal characteristics, fistula between the mass and the anus, contrast enhancement of mass, signal and enhancement of peritumoral areas, and regional lymphadenopathy were assessed.
Most patients (90%) were older than 50 years. There were eight mucinous adenocarcinomas and two adenocarcinomas. The maximum diameter of the tumors ranged from 3.4 cm to 12.4 cm (median: 4.15 cm; mean: 5.68 cm). Eight patients had a fistula between the mass and the anus. Perirectal or inguinal lymphadenopathy was frequent (7/10).
Most lesions of mucinous adenocarcinoma were multiloculated and cauliflower-like, with a thin capsule and focally unclear boundary. They were markedly hyperintense on fat-suppressed T2WI, slightly hyperintense with focal hyperintense on diffusion-weighted imaging (DWI), and hyperintense with focal hypointensity on apparent diffusion coefficient (ADC) map, with progressive mesh-like contrast enhancement.
Adenocarcinomas had an infiltrative margin without a capsule and appeared heterogeneously hyperintense or slightly hyperintense on fat-suppressed T2WI, hyperintense on DWI, and hypointense on ADC map, with persistent heterogeneous enhancement.
A negative biopsy does not rule out the diagnosis of cancer, clinicians should be highly suspicious of cancer in patients with chronic perineal fistulas whose symptoms change, and a repeat biopsy should be recommended. The definitive diagnosis of cancer arising from an anal fistula is always challenging. Although the number of cases was inadequate owing to the rarity of the disease, we believe that several characteristic MRI findings could contribute to accurate and timely diagnosis of carcinoma arising from anal fistula in selection of puncture route and screening of high-risk groups.
Earlier and better identification and monitoring of high-risk groups of carcinoma arising from anal fistula are required.