Multiple benign stromal cell tumours of the small bowel

Are there any prognostic factors for small intestinal stromal tumors?

BACKGROUND

Stromal tumors of the digestive tract, or gastrointestinal stromal tumors (GIST), originate from an intestinal mesenchymal precursor cell. Criteria that predict the outcome of small intestinal stromal tumors (SIST) after surgical resection are not clearly established. The aim of the study was to define prognostic criteria for SIST.

METHODS

All c-kit positive SIST treated in our center over a 10-year period were reviewed.

RESULTS

Eighteen patients with SIST treated by surgical resection were included. Overall actuarial 5-year survival was 74% (median follow-up of 69 months). We developed a panel of five criteria (tumor size, mitotic rate, proliferation index, presence of necrosis, and invasion of mucosa or adjacent structures) that permitted distinction between low and high malignant potential SIST. Presence of any four of these five criteria defined a high malignant potential SIST, and was associated with disease recurrence and poor prognosis after surgical resection (P <0.01). Patients with low malignant potential SIST had a 5-year survival of 92%, compared with 0% for high malignant potential SIST (P <0.01).

CONCLUSIONS

This study demonstrates that a panel of morphologic factors can reliably distinguish between low and high malignant potential SIST. Although patients with low malignant potential SIST have an excellent prognosis after surgical resection, the role of adjuvant treatment for high malignant potential SIST remains to be defined.

Subclassification of gastrointestinal stromal tumors based on evaluation by electron microscopy and immunohistochemistry

Fifty-six gastrointestinal stromal tumors (GIST) were subclassified by ultrastructural examination and by immunophenotypic analysis using a panel of 13 antibodies. Eighty percent of the tumors originated in the stomach and small intestines. The neoplasms were classified as follows: 42.9% smooth muscle tumors (4 leiomyomas, 9 spindle cell and 8 epithelioid leiomyosarcomas, and 3 mixed spindle cell and epithelioid leiomyosarcomas); 37.5% gastrointestinal autonomic nerve tumors (GANT), 47.6% of which arose in the small intestines; 8.9% mixed leiomyosarcoma/neurogenic tumors; and 10.7% undifferentiated GIST, not otherwise specified. The muscle common actin antibody HHF-35, variably reactive with tumor cells composing 23 of 24 smooth muscle tumors, was found to be the most sensitive marker of leiomyocyte differentiation. One immunophenotypically questionable spindle cell leiomyosarcoma was diagnosed by electron microscopy. Since neuron specific enolase positive cells were found in 1/3 of the leiomyosarcoma cases, the ultrastructural demonstration of synapse-like structures and neurosecretory granules was required for diagnosing GANTs. The immunophenotype of the ultrastructurally undifferentiated GIST was vimentin and CD34+. Variable numbers of ultrastructurally undifferentiated cells also we found in all of the tumors except 2 leiomyomas. CD34 was also expressed in smooth muscle (54%) and GAN (62%) tumors. Despite their similar light microscopic appearance, GIST are phenotypically heterogeneous, requiring both ultrastructural and immunohistochemical studies for accurate characterization.