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Gastrointestinal Stromal Tumor (GIST) Presenting as a Huge Pelvic Mass.

ABSTRACT: Gastrointestinal stromal tumors (GISTs) are rare tumors that can arise anywhere in the tubular gastrointestinal tract. These tumors occasionally present as a pelvic mass, leading to a misdiagnosis of gynecological disease. A 47-year-old woman presented with a pelvic mass measuring 30 cm in diameter and highly elevated CA-125 levels. She underwent exploratory laparotomy with resection of the pelvic mass. The mass mimicking ovarian malignancy was found in the sigmoid colon and was correctly diagnosed as a GIST at surgery. It should be noted that preoperative diagnosis of GIST is uncommon, due to its rarity and the varying clinical presentation. However, non-gynecological tumors should be included in the differential diagnosis of a pelvic mass with atypical presentation. Gynecologists need to be cognizant of extra-ovarian pathology in patients presenting with an atypical pelvic mass.

SUBMITTER: Lee T

PROVIDER: S-EPMC3859154 | biostudies-other | 2013 Jan

REPOSITORIES: biostudies-other

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Project description:BACKGROUND:Gastrointestinal stromal tumor (GIST) is the most common primary mesenchymal neoplasm of the gastrointestinal tract. Mutations of KIT and platelet-derived growth factor receptor alpha have been well characterized in GISTs. Patients with KIT mutations are generally sensitive to treatment with tyrosine kinase inhibitors. However, some patients with GIST, while initially sensitive to TKIs, gain resistance in later stages of treatment. Heterologous rhabdomyomsarcomatous dedifferentiation of advanced GISTs after long-term imatinib mesylate (IM) therapy has been reported. In these cases, the underlying molecular mechanism of tumor progression and transformation is unclear. CASE PRESENTATION:We report one such patient with rhabdomyosarcomatous dedifferentiation of a GIST without metastatic disease after brief 3-month therapy with IM. The tumor was composed of two distinct phenotypes, a CD117 negative region with rhabdomyosarcomatous differentiation directly adjacent to a CD117 positive classic GIST region. Molecular analysis identified the activating KIT exon 11 mutation in both regions, indicating a common origin for both phenotypes. Additionally, the dedifferentiated component contained two synonymous variants in platelet-derived growth factor receptor alpha and KIT. The increased number of synonymous variants in the rhabdomyosarcomatous region may reflect increased genetic instability of this tumor that may have resulted in the loss of CD117 expression in the dedifferentiated component. CONCLUSION:This study adds to the growing consensus that rhabdomyosarcomatous GIST progresses from a common GIST primary tumor. The role of IM in this progression is uncertain; however short duration of IM treatment in this study supports the hypothesis that rhabdomyosarcomatous GIST progression is not a consequence of IM therapy. Furthermore, we provide additional information supporting the observation that CD117 negative rhabdomyosarcomatous transformation maintains the activating KIT variant without KIT expression.

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Gastrointestinal Stromal Tumor (GIST) Presenting as a Huge Pelvic Mass.

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