Benign thymic hyperplasia (BTH), more commonly reported in children, can also occur in adults with various cancers concurrently or following chemotherapy.(1) It is thought to be an immunological rebound phenomenon either related to the malignancy or the chemotherapy administered.(2) To our knowledge, this is the first report of BTH following chemotherapy for metastatic uterine leiomyosarcoma.
In March 2001, a 47-year-old woman with pelvic pain was diagnosed with high-grade leiomyosarcoma of the uterus and underwent radical hysterectomy followed by local radiation therapy. A chest CT scan at this time was unremarkable. 3 months later, surveillance CT scans detected bilateral lung nodules, and one measuring 1.1-cm in the right upper lobe. She had no respiratory symptoms at that time. A CT-guided needle aspirate of a right upper lobe nodule confirmed the metastatic nature of her uterine sarcoma. Between September 2001 and March 2002, she received chemotherapy consisting of doxorubicin, ifosfamide, carboplatin and paclitaxel with almost complete resolution of the lung nodules. PET scan in October 2002 did not show any hypermetabolic foci but a CT scan of the chest (Fig 1B) obtained in June 2003 showed a new anterior mediastinal mass measuring 4.3 cm x 3.7 cm not seen in a CT scan from September 2002 (Fig 1A). In July 2003, she underwent a median sternotomy and resection of the mass. The specimen weighed 41 grams and was diagnosed to be BTH (Fig 2). She had an uneventful post-operative course.
Appearance of an anterior mediastinal mass in a patient with malignancy most often is an ominous finding that leads to further invasive tests or surgery to exclude recurrence of disease or a new primary cancer. BTH was described in children recovering from thermal burns and later on recognized as thymic rebound in children following chemotherapy. It is rare in adults and is reported after chemotherapy for lymphomas, testicular germ cell tumors, and sarcomas. BTH can present and co-exist with lymphoma and newly diagnosed testicular germ cell tumors. BTH usually occurs within the first year after chemotherapy, but it can present even 5 years later. Data on nuclear imaging of BTH is limited. BTH can have positive uptake of F-18 fluorodeoxyglucose (FDG) on PET scan (3) and uptake of gallium-67 citrate scintigram, but usually negative on thallium-201 imaging. Tissue confirmation of cancer relapse should be obtained prior to initiating further chemotherapy to avoid the morbidity of unnecessary treatment.(4)
Chest physicians should consider BTH in patients who present with a new anterior mediastinal mass after completion of chemotherapy for a variety of malignancies including metastatic leiomyosarcoma of uterus. Before resorting to median sternotomy and resection, in appropriate patients whose primary cancer is in remission and the CT imaging is suggestive of BTH, nuclear imaging studies could be considered to further evaluate the anterior mediastinal mass. Clinical or radiographic suspicion of BTH in adult cancer patients may allow for a minimally invasive tissue procurement and diagnosis, and obviate the need for surgical resection.
S.K. Vora, None.