Pathological complete response with cocktail chemotherapy in mediastinal seminoma

A mediastinal mass can present a diagnostic challenge, especially when symptoms necessitate urgent treatment. Mediastinal seminoma, a rare extragonadal germ cell tumour, shares clinical features with testicular seminoma, such as slow growth and high sensitivity to chemotherapy and radiotherapy. This case is of a man in his 40s presenting with cough and chest discomfort, with imaging revealing a large anterior mediastinal mass that was causing left diaphragmatic paralysis due to phrenic nerve involvement. Urgent CT of chest, abdomen and pelvis and tissue biopsy supported the diagnosis of mediastinal seminoma, prompting the immediate initiation of chemotherapy with an induction dose of etoposide and cisplatin, followed by the cisplatin, vincristine, methotrexate, bleomycin alternating with actinomycin D, cyclophosphamide, etoposide regimen. This approach led to significant tumour reduction, facilitating complete surgical resection and sparing of the right phrenic nerve. Despite early fluorodeoxyglucose-positron emission tomography suggesting residual activity, resection histopathology confirmed no malignant cells. The patient achieved a favourable outcome, underscoring the importance of rapid treatment initiation, effective chemotherapy regimens and multidisciplinary management in mediastinal seminoma cases.