INTRODUCTION: Mediastinal glomus tumors are rare, highly vascularized tumors of neuroendocrine origin. They arise from chromaffin cells located most frequently in the aortic and carotid paraganglia. 1 Most are non-secreting; symptoms are typically due to compression of adjacent structures. Surgical resection is the standard treatment. However, surgery may be associated with significant bleeding and often patients are not candidates or refuse to undergo surgery. Conventional radiation has been considered a reasonable less invasive alternative to surgery. Nonetheless, it was seldom used due to concerns of excessive late radiation induced toxicity. Recently, extra-thoracic glomus tumors have been effectively treated using robotic radiosurgery. Such treatment appears as effective as conventional radiation while sparing peritumoral late radiation tissue damage. We present the first case of a mediastinal glomus tumor successfully treated with robotic radiosurgery.
CASE PRESENTATION: A 56 year old male with chronic hypertension presented with fevers and a productive cough. A chest radiograph showed no evidence of pneumonia but a mediastinal mass was noted. Computed tomography of the chest was performed; a 4.9 cm by 3.5 cm anterior mediastinal mass was identified with contrast uptake. The patient reported a history of bilateral neck glomus jugulare tumors. He had been successfully treated with surgery and radiation. He did well despite major bleeding during surgery and severe chronic radiation dermatitis. Given his history and the finding of a vascular mediastinal tumor, the patient was diagnosed with a mediastinal glomus tumor. He was a surgical candidate. However, he was unwilling to accept the risks of surgical and conventional radiation treatment a second time. Alternatively, he pursued robotic radiosurgery treatment with tumor tracking (CyberKnife (r)). He wished to have his tumor aggressively irradiated without severe lung or esophageal toxicity. Gold fiducial markers were placed via flexible bronchoscopy to assist tumor tracking during the respiratory cycle. The patient received a total dose of 30 Gy divided in 5 equal treatments. No complications were identified during or following treatment. CT imaging of the chest at 6 months demonstrated significant response with reduction of the mass to 4.0 by 3.1 cm. The patient remains asymptomatic with stable pulmonary function.
DISCUSSIONS: The differential diagnosis of anterior mediastinal masses includes benign and malignant tumors arising from the thymus, thyroid, lymph nodes or the germ-cell line. Thoracic aortic aneurysms are also included. Neuroendocrine tumors are less common, and glomus tumors are especially rare. Eighty percent are sporadic and twenty percent are inherited in an autosomal dominant fashion. Extra-thoracic tumors are most common, and typically arise from head and neck paraganglia. Imaging is essential to guide the diagnosis as these tumors are highly vascular and have intense contrast enhancement both on CT and MRI. Complete surgical resection is the standard of care. Surgery, however, requires cardiopulmonary bypass given the vascular nature and location of these tumors. The role of robotic radiosurgery as a safer and effective modality of therapy has been published for extra-thoracic glomus tumors. 2.
CONCLUSION: Mediastinal glomus tumors should be included in the differential diagnosis of an anterior mediastinal mass. Although complete surgical resection is the standard of care, robotic radiosurgery is an attractive alternative in non-operative candidates and patients who refuse surgery. Our case demonstrates that mediastinal glomus tumors may be responsive to high doses of focused radiation and this can be done safely and effectively. To our knowledge, this is the first case of a mediastinal glomus tumor being treated with robotic radiosurgery.
DISCLOSURE: Jorge Guerrero Espinosa, No Financial Disclosure Information; No Product/Research Disclosure Information