Should asymptomatic enlarged thymus glands be resected?

OBJECTIVE: Patients frequently have an "enlarged thymus" incidentally identified on imaging. We sought to determine whether thymectomy is appropriate in patients with diffusely enlarged thymus glands.
METHODS: A retrospective review was conducted of patients undergoing thymectomy without myasthenia gravis at 1 institution over 15 years.
RESULTS: Of 117 patients undergoing thymectomy, 109 patients had complete data. Thirty-six had a gland judged by the surgeon to be diffusely enlarged, and 73 had a discrete mass. Of the 36 diffusely enlarged thymus glands, 18 (50%) occurred in patients with no symptoms referable to the thymus. No patient (0/18; 0%) with an asymptomatic diffusely enlarged thymus gland had a pathologic diagnosis that would have required resection (8 normal; 10 "hyperplasia"). Of the 18 symptomatic patients with diffusely enlarged glands, 4 (22.2%) harbored lymphoma, but none harbored thymoma or other tumor (P < .05; symptomatic vs asymptomatic). Of the 73 patients with discrete masses, 45 (61.6%) were symptomatic, and both the symptomatic and asymptomatic patients had a high rate of pathologic diagnoses that represented an indication for resection (53.3% and 42.8%, respectively, harbored thymoma or other tumor). Of the 25 (of 109) patients initially having a diagnosis of thymic hyperplasia, only 3 (12%) had true follicular hyperplasia on re-review of the pathologic condition. Interestingly, an autoimmune disorder developed in 2 (67%) of these 3 patients on long-term follow-up.
CONCLUSIONS: Asymptomatic patients with diffusely enlarged thymus glands can be followed up expectantly because they have a negligible incidence of significant thymic disease; symptomatic patients with diffusely enlarged thymus glands may have lymphoma, so biopsy is appropriate. Half of patients with a discrete mass have tumors requiring resection; imaging advances would be useful to better differentiate among patients within this group.