Sporadic pituitary adenoma with somatic double-hit loss of MEN1

Pituitary adenomas commonly arise in patients with MEN1 syndrome, an autosomal dominant condition predisposing to neuroendocrine tumor formation, and typically diagnosed in patients with a relevant family cancer history. In these patients with existing germline loss of MEN1 on one allele, somatic loss of the second MEN1 allele leads to complete loss of the MEN1 protein, menin, and subsequent tumor formation.

Whole exome sequencing was performed on the tumor and matching blood under an institutional board approved protocol. DNA extraction and analysis was conducted according to previously described methods.

We describe a 23 year-old patient with no significant past medical history or relevant family history who underwent surgical resection of a symptomatic and medically resistant prolactinoma. Whole exome sequencing of tumor and blood samples revealed somatic loss of MEN1 at both alleles, suggesting a double hit mechanism, with no underlying germline MEN1 mutation.

To our knowledge, this is the first case of pituitary adenoma to arise from somatic loss of MEN1 and in the absence of an underlying germline MEN1 mutation.