Gastrointestinal stromal tumor in an XYY/XY male.

A 32-year-old patient was diagnosed with a gastrointestinal stromal tumor of the small bowel. The pathologic diagnosis was confirmed by positive immunochemistry against CD34, and against CD117, the tyrosine-kinase c-kit. We performed a karyotypic analysis on the basis of the patient's tall stature and speech difficulties. One hundred thirty-two metaphases were obtained on PHA-stimulated peripheral blood; 123 of them presented an extra chromosome Y. Fluorescence in situ hybridization using a Y satellite III probe showed the presence of a sole copy of chromosome Y in the tumor cells precluding a direct relationship between the extra chromosome Y and the initiation of the tumor. This is, to our knowledge, the second occurrence of a nonhematologic malignancy reported in this genetic disorder. A review of the malignancies observed in men with the XYY constitution is presented.