Perivascular epithelioid cell tumors of gastrointestinal tract (GI
PEComas) are exceedingly rare, with only a limited number of published reports worldwide. Given the scarcity of GI
PEComas and their relatively short follow-up periods, our current knowledge of their
biologic behavior, molecular genetic alterations, diagnostic criteria, and prognostic factors continues to be very limited.We present 2 cases of GI
PEComas, one of which showed an aggressive histologic behavior that underwent multiple combined
chemotherapies. We also review the available English-language medical literature on GI
PEComas-not otherwise specified (
PEComas-NOS) and discuss their clinicopathological and molecular genetic features.Pathologic analyses including histomorphologic, immunohistochemical, and ultrastructural studies were performed to evaluate the clinicopathological features of GI
PEComas, their diagnosis, and differential diagnosis. Immunohistochemistry, semiquantitative
reverse transcriptase polymerase chain reaction, and
DNA sequencing assays were carried out to detect the potential molecular genetic alterations in our cases. Microscopically, the
tumors showed distinctive histologic features of
PEComas-NOS, including fascicular or nested architecture, epithelioid or spindled cell type, and clear to eosinophilic cytoplasm. The
tumor cells were immunohistochemically positive for melanocytic markers. Molecular pathological assays confirmed a PSF-TFE3 gene fusion in one of our cases. Furthermore, in this case
microphthalmia-associated transcription factor and its downstream genes were found to exhibit elevated transcript levels.Knowledge about the molecular genetic alterations in GI
PEComas is still limited and warrants further study.