Should asymptomatic enlarged thymus glands be resected?

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.

A retrospective review was conducted of patients undergoing thymectomy without myasthenia gravis at 1 institution over 15 years.

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.

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.