Loss of genes on chromosome 22 in medullary thyroid carcinoma and pheochromocytoma.

Using polymorphic DNA markers, we compared the constitutional and tumor genotypes of patients with multiple endocrine neoplasia type 2A (MEN2 A). We found loss of constitutional heterozygosity at the D22S9 locus in one out of 9 medullary thyroid carcinomas (MTCs). No loss of heterozygosity was detected at 12 other loci in any of the MTCs tested. Loss of heterozygosity at D22S9 and/or D22S1 was also demonstrated in 2 out of 5 pheochromocytomas tested. These results suggest that loss or mutation of a gene on chromosome 22 may play an important role in tumorigenesis in MEN2A.