Anal canal gastrointestinal stromal tumors: Case report and literature review

Abstract

Gastrointestinal stromal tumors (GIST) are an uncommon group of tumors of mesenchymal origin. GIST of the anal canal is extremely rare. At present, only 10 cases of c-kit positive anal GIST have been reported in the literature. There is no widely accepted treatment approach for this neoplasia. Literature is sparse on imaging evaluation of anal canal GIST, usually described as a lesion in the intersphincteric space. We describe the case of a 73-year-old man with a mass in the anal canal, and no other symptoms. Endoanal ultrasound and magnetic resonance imaging showed a well circumscribed solid nodule in the intersphincteric space. The patient was treated by local excision. Gross pathological examination showed a 7 cm × 3.5 cm × 3 cm mass, and histological examination showed a proliferation of spindle cells, with prominent nuclear palisading. The mitotic count was of 12 mitoses/50 HPF. The tumor was positive for KIT protein, CD34 and vimentin in the majority of cells, and negative for desmin and S100. A diagnosis of GIST, with high risk aggressive behavior was made. An abdomino-perineal resection was discussed, but refused. The follow-up included clinical evaluation and anal ultrasound. After 5 years the patient is well, with maintained continence and no evidence of local recurrence.

Unusual Mesenchymal Tumors of the Lower Gastrointestinal Tract: When You Hear Hoofbeats in the Night, Do Not Forget the Zebras

“…The differential diagnosis between GIST and spindle cell melanoma represents a potential diagnostic pitfall and is normally based on morphology and IHC. It is known that GISTs may express anti-S100 protein antibodies [13], but in the literature, there is no agreement about the expression of Melan A in GISTs [14, 15]. On the other hand, melanoma can also express c-Kit (CD117) up to 40% of cases (positive 16/40 cases) [16].…”

Wide local excision for anal GIST: A case report and review of literature

“…Endorectal ultrasound (ERUS) is used for determining the depth of the lesion. Typically, GIST appears as a well circumscribed hypoechoic mass arising from the intersphincteric space encroaching into the lumen on ERUS [12]. Lymphadenopathy is absent.…”

“…Anal sphincters get involved as the lesion increases in size. Alternatively, magnetic resonance imaging (MRI), CT abdomen and pelvis can be performed for staging the disease [9], [12].…”

“…Due to its potential for malignant behavior, most of the previously reported cases were treated by radical surgery such as abdominoperineal resection (APR) and pelvic exentration [4], [5], [6], [7], [8], [9], [10]. But some anecdotal cases have been treated successfully by local excision [1], [11], [12]. Whether it is oncologically acceptable to perform local excision for anal GIST is not known.…”

Tumours and inflammatory lesions of the anal canal and perianal skin revisited: an update and practical approach

“…The anal canal is a rare site for gastrointestinal stromal tumour (GIST), comprising around 3–5% of all GISTs 60 61. They usually present as a mural nodule, and more rarely as a pelvic mass.…”