Alveolar soft part sarcoma of the thyroid gland in a child☆

Background: Soft tissue sarcomas, including rhabdomyosarcomas (RMS) and non-RMS (NRSTS), are rare in children with less than 1000 new cases diagnosed yearly in the United States. RMS is the most common soft tissue sarcoma in young children and NRSTS is more common in adolescents and young adults. Alveolar soft part sarcoma (ASPS) is a form of NRSTS. ASPS is an extremely rare malignancy, comprising less than 0.1% of head and neck sarcomas. In children, ASPS has a tendency for the head and neck region (27%), with most cases involving the orbit and the tongue. Methods: A 2-year-old boy presented with respiratory distress. Imaging revealed a 5.5cm×4.0cm×2.5cm mass arising from the thyroid gland compressing the trachea and bilateral pulmonary metastases. Results: The patient underwent tracheostomy, thyroid lobectomy, and excision of paralaryngeal/paratracheal tissue. Pathology revealed positive margins and extensive lymphovascular permeation. Discussion: Cases of ASPS of the larynx, buccal space, paravertebral space, orbit, and tongue have been described. This is the first case of primary ASPS of the thyroid gland. Surgery is the mainstay of treatment for NRSTS, and radiation and chemotherapy are reserved for the subset of NRSTS that are high grade or unresectable. Median survival time of patients with ASPS is 3 years if metastatic disease is present at the time of diagnosis and 11 years if there is no metastatic disease at presentation. Our patient survived 2 years after diagnosis. Conclusion: Even though very rare, ASPS should be considered in the differential diagnosis of thyroid tumors.