Thymic rebound after adjuvant chemotherapy in breast cancer: a case report

Chemotherapy, especially for malignant tumors, can affect the thymus, leading to its atrophy and a decreased production of naïve T lymphocytes. However, regenerative process can occur in children and rarely in adults manifesting as thymic hyperplasia. A 49-year-old female patient was diagnosed with stage I breast cancer. She was treated with surgery, adjuvant chemotherapy followed by radiotherapy and hormonotherapy. Follow-up computed tomography scan showed a mediastinal retro-sternal mass, raising concern for tumor recurrence. However, no other signs of relapse were evident. A thymic rebound was suspected, with the lesion presenting as a triangular-shaped mediastinal mass suggestive of thymic morphology and consisting of mixed fat and soft tissue density with smooth borders. Close monitoring was then decided. A follow-up CT scan of the chest showed regression of the mediastinal mass. The diagnosis of thymic rebound after chemotherapy was then retained. The patient is currently in remission, seven years from her original diagnosis of breast cancer. Thymic hyperplasia after chemotherapy can rarely occur in adults. Clinicians should be aware of this unusual presentation to prevent needless investigation and therapy.