Glomus tumors in individuals with neurofibromatosis type 1. 
Glomus tumors have recently been reported in individuals with the neurofibromatosis type 1 (NF1) cancer disposition syndrome.  We compare the clinical and molecular features of these painful hamartomas in a series of sporadic and NF1-associated cases.  We sought to evaluate the association of NF1 with glomus tumors and to compare NF1-associated glomus tumors with sporadic glomus tumors.  We conducted a retrospective cohort study of all individuals with a histopathologic diagnosis of glomus tumor at a large tertiary care center from January 1998 to January 2013.  Charts were reviewed for a coexisting diagnosis of NF1.  A total of 42 glomus tumors were identified in 34 individuals.  Twelve (28.6%) were found in 6 patients with NF1.  In 28 individuals with 30 sporadic tumors, there was no coexisting medical condition.  Although multifocal tumors (16.7%) and tumor recurrence (33.3%) were more common in association with NF1, these trends did not reach statistical significance.  NF1-associated glomus tumors exhibited no neurofibromin immunoreactivity, whereas their sporadic counterparts retained neurofibromin expression.  The retrospective design resulted in incomplete data capture.  Detection of glomus tumors should raise suspicion for a concurrent diagnosis of NF1.