LOH affecting the MEN1 gene in a tumor is highly suggestive of causality but not always conclusive, given that genomic loss of 11q13 can also occur in sporadic neuroendocrine tumors (9–11) and also due to the possibility that deletions of other genes contiguous to MEN1 on chromosome 11q13 may actually be responsible for a particular clinical phenotype. This evidence concerns the gene MEN1 and neoplasm.