Mixed Germ Cell Tumor (Stage IV): Clinical Case of Tumor Regression and Recovery

Approximately one year prior, Fauzan presented with a very large thoracic malignancy, with imaging documenting a pulmonary mass measuring up to 18 cm. Clinically, he had severe, persistent cough and orthopnea, rendering him unable to lie supine and requiring a semi-recumbent position for rest. He also experienced significant cancer-associated cachexia, with an unintentional weight loss of 15 kg over six months.

CT of the thorax demonstrated a massive space-occupying lesion involving the entire left lung, causing marked mediastinal shift with displacement of the heart, trachea, and esophagus toward the contralateral (right) hemithorax. There was evidence of bilateral pulmonary involvement with metastatic nodules in the right lung, as well as hepatic metastases. Histopathological evaluation via biopsy confirmed a malignant mixed germ cell tumor. A bone scan further revealed osseous metastasis involving the skull, indicating disseminated (stage IV) disease.

Given the advanced tumor burden, the risk of complications related to rapid tumor necrosis was a concern. During consultation in September 2024, the ECCT team explained that while electric field–based therapy may induce tumor cell death, the patient’s physiological capacity to clear necrotic cellular debris could be limited. This raises the theoretical risk of exaggerated inflammatory responses, including tumor lysis–related complications or cytokine-mediated systemic effects. Therefore, a combined modality approach was advised, with standard systemic chemotherapy forming the backbone of treatment, alongside ECCT as a complementary modality.

The patient initiated systemic chemotherapy in January 2025, approximately three months after commencing ECCT therapy. Germ cell tumors are generally considered highly chemosensitive malignancies, particularly to platinum-based regimens. Following the first cycle of chemotherapy, interval CT imaging demonstrated a marked reduction in tumor size, from approximately 16 cm to 7.6 cm, consistent with a strong treatment response. Subsequent imaging showed continued, albeit slower, reduction in residual mass.

Post-treatment reassessment, including repeat biopsy, indicated that the residual lesion consisted predominantly of fibrotic tissue without viable malignant cells, suggesting a radiographic residual mass rather than active disease, a known outcome in treated germ cell tumors due to fibrosis or necrosis replacing tumor tissue.

From a pathophysiological perspective, this reflects effective cytotoxic therapy leading to tumor cell apoptosis/necrosis, followed by reparative fibrosis. In such cases, residual masses may persist radiologically despite complete pathological response.

The patient continued ECCT use in a maintenance/preventive context. At one-year follow-up from initiation of therapy, he demonstrated significant clinical recovery, including return to functional baseline and resumption of work. Serial imaging showed stability of the fibrotic residual in the left lung, with no evidence of progression.