Answer for BIR CoW 27 Feb 2022
RECTAL GIST
Findings
Evidence of well defined lobulated T1 iso to hypointense, T2 heterointense lesion measuring 7.3 cm (cranio caudal) x 6.5 cm (anteroposterior) x 7.9 cm (transverse) noted arising from the intramural plane of left lateral wall of rectum. Lower border of the lesion is seen about 3.6 cm proximal to anal verge. The lesion shows diffusion restriction with low ADC values and causes extrinsic compression and narrowing of lumen of rectum with preservation of surrounding fat planes. No evidence of perirectal/ pelvic lymphadenopathy Features suggestive of rectal GIST. Histopathology: Gastrointestinal stromal tumor, DOG 1 positive.
Discussion
Gastrointestinal stromal tumors (GISTs) are currently the most common nonepithelial tumors of the gastrointestinal tract. GISTs are now thought to derive from a precursor of the interstitial cells of Cajal, normally present in the myenteric plexus, and are clearly distinct from other mesenchymal tumors, such as leiomyomas or leiomyosarcomas. The interstitial cells of Cajal normally express a trans-membrane receptor tyrosine kinase encoded by the KIT gene. These tumours occur most frequently in the stomach (70%) and small intestine (20-30%). Rectal GIST is uncommon and accounts for approximately 5% of GIST. They typically originate from the muscularis propria and have a propensity for exophytic growth with delayed clinical presentation. Symptoms include rectal pain or fullness, rectal bleeding, or are discovered incidentally on routine digital rectal examination. CT is currently the modality of choice for diagnosis, although other imaging techniques such as MRI and endorectal ultrasound can also be used. They are typically large, exophytic, well-circumscribed, hyper vascular tumours, which enhance heterogeneously due to necrosis, haemorrhage or cystic degeneration. On MRI GIST are of uniform intermediate signal on T1 and heterogenous high signal on T2 weighted imaging. Immunohistochemically, virtually all (95%) GISTs are positive for KIT (CD117). For localized primary GISTs, surgical resection is the mainstay of therapy. Use of a pre-operative biopsy of suspected GISTs has been controversial because of the potential risks of hemorrhage and tumor seeding into the peritoneal cavity. Unresectable primary or recurrent GIST can now be treated with a tyrosine kinase receptor inhibitor, imatinib, with good response. Although GIST of the rectum is rare, it should be considered in the differential diagnosis of rectal masses as treatment and follow up differs from the more common rectal tumours.
References:
1. DeMatteoRP. The GIST of targeted cancer therapy: a tumor (gastrointestinal stromal tumor), a mutated gene (c-kit), and a molecular inhibitor (STI571). Ann Surg Oncol2002;9(9):831–839.
2. JoensuuH, Roberts PJ, Sarlomo-Rikala M, et al. Effect of the tyrosine kinase inhibitor STI571 in a patient with a metastatic gastrointestinal stromal tumor. N Engl J Med2001;344:1052–1056.
3. Gastrointestinal Stromal Tumor: Role of CT in Diagnosis and in Response Evaluation and Surveillance after Treatment with Imatinib. Xie Hong, Haesun Choi, Evelyne M. Loyer, Robert S. Benjamin, Jonathan C. Trent, Chusilp Charnsangavej
Findings
Evidence of well defined lobulated T1 iso to hypointense, T2 heterointense lesion measuring 7.3 cm (cranio caudal) x 6.5 cm (anteroposterior) x 7.9 cm (transverse) noted arising from the intramural plane of left lateral wall of rectum. Lower border of the lesion is seen about 3.6 cm proximal to anal verge. The lesion shows diffusion restriction with low ADC values and causes extrinsic compression and narrowing of lumen of rectum with preservation of surrounding fat planes. No evidence of perirectal/ pelvic lymphadenopathy Features suggestive of rectal GIST. Histopathology: Gastrointestinal stromal tumor, DOG 1 positive.
Discussion
Gastrointestinal stromal tumors (GISTs) are currently the most common nonepithelial tumors of the gastrointestinal tract. GISTs are now thought to derive from a precursor of the interstitial cells of Cajal, normally present in the myenteric plexus, and are clearly distinct from other mesenchymal tumors, such as leiomyomas or leiomyosarcomas. The interstitial cells of Cajal normally express a trans-membrane receptor tyrosine kinase encoded by the KIT gene. These tumours occur most frequently in the stomach (70%) and small intestine (20-30%). Rectal GIST is uncommon and accounts for approximately 5% of GIST. They typically originate from the muscularis propria and have a propensity for exophytic growth with delayed clinical presentation. Symptoms include rectal pain or fullness, rectal bleeding, or are discovered incidentally on routine digital rectal examination. CT is currently the modality of choice for diagnosis, although other imaging techniques such as MRI and endorectal ultrasound can also be used. They are typically large, exophytic, well-circumscribed, hyper vascular tumours, which enhance heterogeneously due to necrosis, haemorrhage or cystic degeneration. On MRI GIST are of uniform intermediate signal on T1 and heterogenous high signal on T2 weighted imaging. Immunohistochemically, virtually all (95%) GISTs are positive for KIT (CD117). For localized primary GISTs, surgical resection is the mainstay of therapy. Use of a pre-operative biopsy of suspected GISTs has been controversial because of the potential risks of hemorrhage and tumor seeding into the peritoneal cavity. Unresectable primary or recurrent GIST can now be treated with a tyrosine kinase receptor inhibitor, imatinib, with good response. Although GIST of the rectum is rare, it should be considered in the differential diagnosis of rectal masses as treatment and follow up differs from the more common rectal tumours.
References:
1. DeMatteoRP. The GIST of targeted cancer therapy: a tumor (gastrointestinal stromal tumor), a mutated gene (c-kit), and a molecular inhibitor (STI571). Ann Surg Oncol2002;9(9):831–839.
2. JoensuuH, Roberts PJ, Sarlomo-Rikala M, et al. Effect of the tyrosine kinase inhibitor STI571 in a patient with a metastatic gastrointestinal stromal tumor. N Engl J Med2001;344:1052–1056.
3. Gastrointestinal Stromal Tumor: Role of CT in Diagnosis and in Response Evaluation and Surveillance after Treatment with Imatinib. Xie Hong, Haesun Choi, Evelyne M. Loyer, Robert S. Benjamin, Jonathan C. Trent, Chusilp Charnsangavej
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!