Extragastrointestinal (Soft Tissue) Stromal Tumors: An Analysis of 48 Cases with Emphasis on Histologic Predictors of Outcome

Abstract

The clinicopathologic features of 48 tumors that were histologically similar to gastrointestinal stromal tumors but occurred in the soft tissues of the abdomen were analyzed to determine their overall similarity to their gastrointestinal counterpart, their biologic behavior, and the parameters that predict risk for adverse outcome. Classic leiomyomas and leiomyosarcomas were specifically excluded. The tumors occurred in 32 women and 16 men, who ranged in age from 31 to 82 years (mean, 58 years). Forty tumors arose from the soft tissue of the abdominal cavity, and the remainder arose from the retroperitoneum. They ranged in size from 2.1 to 32.0 cm and varied from tumors composed purely of rounded epithelioid cells to those composed of short fusiform cells set in a fine fibrillary collagenous background with some cases showing a mixed pattern. Tumors displayed variable amounts of stromal hyalinization, myxoid change, and cyst formation. The tumors expressed CD117 (c-kit receptor) (100%), CD34 (50%), neuron-specific enolase (44%), smooth muscle actin (26%), desmin (4%), and S-100 protein (4%). Tumors were evaluated with respect to several parameters: size (<10 cm or >10 cm), cellularity (low or high), mitoses (0 to 2 per 50 high-power fields, >2 per 50 high-power fields), nuclear atypia (1 to 3؉), cell type (epithelioid, spindled, or mixed), and necrosis (absent or present). These parameters were then evaluated in univariate and multivariate analysis with respect to adverse or nonadverse outcome, the former defined as metastasis or death from tumor. Follow-up information was obtained for 31 patients (range, 4 to 84 months; median, 24 months). One patient presented with an adverse event and, therefore, was excluded from subsequent analysis. Twelve patients (39%) developed metastases or died of tumor. In univariate analyses, cellularity, mitotic activity (>2 per 50 high-power fields), and necrosis were associated with statistically significant increases in the risk for adverse outcome. Despite the relatively small sample size, in a multivariable analysis mitotic activity (relative risk, 7.46; P ‫؍‬ .09) and necrosis (relative risk, 3.75; P ‫؍‬ .07) displayed trends toward independent predictive value. Mesenchymal tumors that arise from the wall of the gastrointestinal tract have attracted a great deal of attention over the years. It is generally accepted that those that arise from the esophagus and rectum recapitulate the appearance of mature smooth muscle (1-3), whereas the vast majority of tumors that arise from the remainder of the gastrointestinal

Primary gastrointestinal stromal tumor of the liver in an anorectal melanoma survivor: A case report

“…The majority of GISTs arise in the stomach and small intestine, and GISTs originating from the esophagus, colon and extra-gastrointestinal organs, such as the retroperitoneum and liver, are rare (6). To the best of our knowledge, only five cases of primary hepatic GIST have previously been reported in the English literature (7)(8)(9)(10)(11).…”

Differential expression of KIT/PDGFRA mutant isoforms in epithelioid and mixed variants of gastrointestinal stromal tumors depends predominantly on the tumor site

“…[1][2][3] Occasionally, primary GISTs have been reported outside the gastrointestinal tract, specifically in the omentum, mesenteries, and retroperitoneum. 4,5 Histologically, these neoplasms are usually composed of spindle cells (70%) or less frequently of epithelioid (20%) or mixed, epithelioid and spindle cell types (10%). 6 Lesions of mixed cell type may exhibit a transition between spindle and epithelioid areas, or may have both cell types intermingled throughout the tumor specimen.…”

Association of Matrix Metalloproteinase (MMP)-2 and -9 Expression with Extra-gastrointestinal Stromal Tumor Metastasis

“…Although they are similar to gastrointestinal stromal tumors (GISTs) in terms of histopathology and immunophenotypes (Reith et al, 2000), there are various differences between EGISTs and GISTs, such as tumor size, necrosis, and tumor cell mitotic rate. GISTs are one of the most common mesenchymal tumors with Kit or PDGFRA gene mutations (Wang et al, 2013).…”