Embryonal rhabdomyosarcoma arising from a mediastinal teratoma: an unusual case report

Genomic profiling of a metastatic anaplastic melanocytic neuroectodermal tumor arising from a mature thymic teratoma as part of a mediastinal germ cell tumor

Following chemotherapy, a mediastinal germ cell tumor can lead to a mature teratoma that is composed of tissues derived from all three germ layers. Although teratoma is usually curable, in rare cases it can give rise to various somatic tumors and exceptionally it undergoes melanocytic neuroectodermal tumor (MNT) transformation, a process that is not well-described. We report a patient with a postchemotherapy thymic teratoma associated with an MNT component who, 10 years later, additionally presented a vertebral metastasis corresponding to an anaplastic MNT. Using exome sequencing of the mature teratoma, the MNT and its metastatic vertebral anaplastic MNT components, we identified 19 somatic mutations shared by at least two components. Six mutations were common to all three components, and three of them were located in the known cancer-related genes KRAS (p.E63K), TP53 (p.P222X), and POLQ (p.S447P). Gene set enrichment analysis revealed that the melanoma tumorigenesis pathway was enriched in mutated genes including the four major driver genes KRAS, TP53, ERBB4, and KDR, indicating that these genes may be involved in the development of the anaplastic MNT transformation of the teratoma. To our knowledge, this is the first molecular study realized on MNT. Understanding the clinicopathological and molecular characteristics of these tumors is essential to better understand their development and to improve therapeutics.

Mediastinal Mature Teratoma With Malignant Carcinomatous Transformation (Somatic-Type Malignancy) With Metastatic Course

We report the case of a 76-year-old patient presenting with an anterior mediastinal heterogeneous mass. Surgical biopsy revealed a solid and cystic lesion filled with hair. Pathological examination showed an atypical papillary epithelial lining without other germ cell tumor or immature teratoma associated. The final diagnosis was a mature teratoma of the mediastinum with somatic-type malignancy (carcinomatous transformation). After 8-month follow-up, subcutaneous and lymph node metastatic lesions of the carcinomatous component were identified. Subtyping of the malignant component within germ cell tumors is an important challenge for therapeutic options and prognosis.