[PRIMARY MEDIASTINAL GERM CELL TUMOR ARISING IN A PATIENT WITH NEUROFIBROMATOSIS TYPE 1].

Neurofibromatosis type 1 (NF1) is a distinct genetic disorder due to the NF1 gene mutation which induces the aberrant activation of the RAS-signaling. Because RAS-related proteins function as oncogenic factors, NF1 patients frequently develop malignant tumors, especially of neural crest origin, such as peripheral nerve sheath. In addition, malignant tumors of the pancreas, colorectum, and lung have been reported to frequently arise in NF1 patients. However, the association between germ cell tumor and NF1 has not been clarified yet. A 29-year-old male with dyspnea was referred to our hospital because of the large mass in the anterior mediastinum and cervical lymph node swelling. The diagnosis was extragonadal germ cell tumor with cervical lymph node metastasis, and complete remission was obtained by multidisciplinary treatment consisted of combination chemotherapy and surgical resection. To our acknowledgement, this is the first case of extragonadal germ cell tumor in NF1 patients. We discuss the relevance between activation of the RAS-signaling and the development of germ cell tumor.