Anal canal gastrointestinal stromal tumors - report of a rare case and review of the literature

Abstract

Background: Gastrointestinal stromal tumors (GISTs) are considered as rare gastrointestinal tumors, and their location in the anal track is exceptionally unusual. We describe the case of a 28-year-old man with anal GIST, and a review of the cases that have been reported so far in the literature.

Case report: The patient was referred for treatment of a gradually enlarging perianal mass. Clinical examination and imaging including orthosigmoidoscopy, transanal ultrasound, and magnetic resonance imaging (MRI) revealed a mass sized 7.5 cm in greatest diameter, in relation with the sphincters, which was excised under general anesthesia. His postoperative course was uneventful and he was discharged on the fourth postoperative day. Pathologic examination revealed characteristics of anal GISTs and further treatment with tyrosine kinase inhibitors was planned.

Conclusion: Anal GISTs usually present with rectal bleeding and pain, and only sixteen cases have been reported in the literature. MRI is the radiologic examination of choice, while optimal treatment is considered surgery in combination with adjuvant therapy. Long-term follow-up is necessary. Hippokratia 2016, 20(4): 313-316.

Keywords: GIST; Gastrointestinal stromal tumor; anal canal; surgery.

Figure 1. A) Clinical photo showing the presence of a sizeable left perianal mass, B and C) intraoperative photos demonstrating complete excision of the mass with clear surgical margins.

Figure 2. A) Transanal ultrasound showed an anal mass and B) sagittal magnetic resonance imaging showing a lobular tumor of heterogeneous signal, without central enhancement.

Figure 3. Dense and diffuse immunoreactivity of the neoplastic cells for antigens CD117 (A) and CD34 (B) (x400, immunoperoxidase with hematoxylin counterstain).