Sclerosing thymoma followed up for eight years as mediastinal goiter: A case report

INTRODUCTION: Sclerosing thymoma (ST) is an extremely rare disease with less than 20 cases ever been described. Here, we present a case of sclerosing thymoma that was followed up as mediastinal goiter for eight years. PRESENTATION OF CASE: A 77-year-old man was presented with a superior mediastinal tumor. The patient was asymptomatic and not affected by myasthenia gravis. Computed tomography showed a well-defined superior mediastinal tumor whose size had regressed over time. Ultrasonography-guided core-needle biopsy revealed type B1 to B2 thymoma, and total-thymectomy was performed. Histopathologically, most of the tumor showed hyalinization and sclerosis, and slight signs of type AB thymoma were found at the tumor’s periphery. The patient was diagnosed with ST. No evidence of recurrence was observed 12 months following surgery. DISCUSSION: Since sclerosing thymoma is mostly composed of fibrous tissue, small specimens such as needle biopsies do not contain tumor cell nests and are difficult to confirm. Complete resection is currently the most common treatment for ST. Spontaneous regression of ST has been reported; however, the mechanisms involved have not yet been elucidated. CONCLUSION: This rare case of sclerosing thymoma is an unusual case since it has follow up information for an eight year period due to the misdiagnosis of goiter. The follow up visits showed significant regression of the tumor over the eight year period without treatment; however, the etiology of sclerosis and regression remain unknown. The patient was treated by thymectomy with no recurrence after 12 months.