Mediastinal germ cell tumors

Abstract

Mediastinal germ cell tumors are rare malignancies that originate from the reproductive cells of the ovaries or testicles. They typically occur in the gonadal region, but can also develop outside of the gonads in 1 to 5% of cases. These tumors arise from remnants of mislocated primordial germ cells along the midline of embryonic migration and are referred to as \"extragonadal germ cell tumors.\" The most common sites for extragonadal GCTs are the mediastinum, retroperitoneal region, suprasellar region, and pineal gland. Tumors that arise in the mediastinum are called primary mediastinal (PM) GCTs and are the most frequently seen type of extragonadal GCT. These tumors are typically located in the anterior compartment, around the thymic lobe, but lesions originating from the posterior mediastinum, pericardium, and aortic adventitia have also been reported. While benign germ cell tumors are more commonly seen in females and children, the majority of malignant mediastinal germ cell tumors occur in late adolescence and adult males. It has been reported that nearly 90% of PMGCTs are diagnosed in males in their 3rd to 5th decades of life, and the tumors are typically located in the anterior mediastinum. PMGCTs are a group of tumors that exhibit a wide variation in histopathology, clinical features, and treatment approaches. It is typical to categorize these tumors into two main categories: seminomas and non-seminomatous GCTs. Seminomas are malignant germ cell tumors that primarily affect the testicles or, less commonly, the mediastinum, retroperitoneum, or other extragonadal regions. Seminomas are the second most common type of PMGCT, typically occurring in males between the ages of 20 and 45, and are not found in prepubertal patients. Seminomas often grow slowly, reaching a considerable size (5-20 cm) and sometimes appearing as lobulated masses before symptoms arise. Symptoms occur as the mass compresses adjacent anatomical structures and can include chest pain, dyspnea, dysphagia, dysphonia, cough, weight loss, and superior vena cava syndrome. In 60-70% of patients, metastasis to the bone, liver, lymph nodes, lungs, or brain, which indicates a poor prognosis, is detected at the time of diagnosis. The diagnosis of seminoma is definitively excluded. The treatment approach for primary mediastinal seminoma has been standardized, with systemic chemotherapy being the primary approach. Surgery has a limited role in the treatment of mediastinal seminomas. Salvage surgery is recommended in the presence of a residual tumor larger than 3 cm after chemotherapy.