We studied 6 medullary thyroid carcinomas and 1 C-cell hyperplasia specimen from 7 patients with MEN 2A and known RET germline mutations for allelic imbalance at the RET locus and for somatic genetic alterations at the VHL gene locus at 3p25/26 including LOH and mutations (Table 1). The gene discussed is RET; the disease is multiple endocrine neoplasia type 2A.