mutation, c.1777C>T, identified in a patient with multiple cancers
and a family history remarkable for autosomal dominant, early
age melanocytic tumors and cutaneous melanomas. The
c.1777C>T mutation introduces a premature stop codon into
the BAP1 open reading frame with resultant expression of a
truncated protein. Immunohistochemical (IHC) assessment of
the melanocytic tumors from this family documented loss of
BAP1 protein expression within neoplastic cells. Additionally,
IHC analysis of a thyroid papillary carcinoma and a thyroid
adenoma arising in the proband carrying the c.1777C>T mutation
germline mutation demonstrated loss of BAP1 protein
expression in these tumors. The results of our investigation
suggest that loss of BAP1 tumor suppression contributes to
the development of thyroid cancers, expands the clinical phenotype
of the BAP1-associated tumor predisposition syndrome
and underscores the increasing importance of recognizing this
syndrome in the evaluation of suspected hereditary cancers.
Finally, the current investigation provides further insight in
the molecular pathobiology associated with loss of BAP1
expression.