[Thymic hyperplasia following treatment for nephroblastoma]

Thymic hyperplasia in response to stress is a well known phenomenon. Thymic hyperplasia has also been described after chemotherapeutic treatment for malignancies in children.

A three-year-old girl was followed up from the age of 18 months for a left kidney nephroblastoma treated by combination of chemotherapy (vincristin, actinomycin and adriamycin) and surgery. Assessment at the end of treatment was normal. Four months after the end of treatment, pulmonary radiography showed mediastinal enlargement, which was shown to originate in the thymus at thoracic CT scan. A recurrence of the disease was suspected. Biopsy showed thymic hyperplasia without evidence of tumor cells. Mediastinal enlargement then disappeared spontaneously 2 months later.

Thymic hyperplasia occurring during remission of a cancer treated by chemotherapy is a diagnostic dilemma as it suggests mediastinal reccurence of the disease. Needle aspiration cytology is an appropriate investigation in thymic hyperplasia. No steroid therapy should be used before histologic diagnosis of thymic hyperplasia.