Embryonal Rhabdomyosarcoma Arising from a Mediastinal Teratoma: An Unusual Case Report
A 46-yr-old man presented with chest trauma as a result of an accident on 10 September 2011. On chest X-ray, an anterior mediastinal mass was detected (). To obtain further information, chest computed tomography (CT) with contrast enhancement was performed, revealing a 9.5-cm-sized anterior mediastinal mass (). The initial radiological diagnosis was thymoma. The radiological differential diagnoses were germ cell tumor and mediastinal sarcoma. Clinical and ultrasonography examination of the testicles were normal. Complete surgical excision was performed and entire specimen was evaluated. Grossly, the specimen showed a well-circumscribed 9.5 × 8 × 6-cm-sized round firm mass that was covered with normal thymic and perithymic soft tissue (). The cut surface was flesh-colored and pale tan appearances (). Microscopically, tumor demonstrated two different areas, including mature teratoma and sarcomatous area. In the teratoma area, the tumor demonstrated mature squamous epithelium, hair, skin appendage, adipose tissue, and other mesenchymal tissue (). Immature components were not identified. There is also intermingled areas compact cellular and loose and myxoid area (). In the sarcomatous area, there is some histological architecture resembled embryonic muscle, which forms aggregates of myoblasts amid loose, myxoid mesodermal tissue. The myoblastic tumor showed sheets of rhabdoid cells, which were small and spindled in appearance, and demonstrated moderate to poor differentiation. The cell also demonstrated deeply eosinophilic cytoplasm, and small eccentric oval-shaped nuclei (). Immunohistochemical (IHC) analysis revealed a strong positivity to anti-myogenin and anti-desmin antibodies in the rhabdomyosarcoma component (). The surgical resection margin was clear. After surgical excision, two cycles of dactinomycin-based chemotherapy were performed. Lung metastasis was detected on follow up CT on September 2012, and wedge resection was performed. Pathological finding of lung lesion showed same feature with that of primary rhabdomyosarcoma.