e17008 Background: Germ cell tumors are the most common cancer in men between 15 and 40, with a primary testicular tumor in 95% of cases. In rare instances, this primary tumor may spontaneously regress — a phenomenon known as a “burned-out testicular tumor » (BOTT). It mainly involves pure seminomas, showing clinical and histological regression along with a characteristic appearance on scrotal imaging. We have identified a similar phenomenon of spontaneous regression of lymph node metastases. This newly recognized clinical entity should be acknowledged and considered in treatment and follow-up. Methods: We reviewed retrospectively all new diagnoses of metastatic germ cell tumors between January 1, 2020, and August 31, 2025 in two high-volume French centers. Patients with sequential conventional and metabolic imaging and histological evidence confirming the phenomenon of burned-out lymph nodes (BOLNs) were identified. Data on patient characteristics, treatment, serum tumor markers and lymph node size over time were collected. Results: From January 2020 to August 2025, we identified five cases. The median age was 30.5 years (range 19–49 years). All patients were diagnosed with pure seminoma, histologically confirmed either from the primary tumor (4/5) or from lymph node biopsies. The median lymph node size at diagnosis was 18 mm (range 12–35 mm). In four out of five patients, the lymphadenopathies were ipsilateral retroperitoneal nodes relative to the testicular tumor; in one patient, they were mediastinal nodes, with biopsy confirming the presence of seminoma. All patients underwent baseline CT and 18F-FDG PET scans, repeated at least twice, showing partial morphological regression and complete metabolic response in all cases. Only one patient has so far required chemotherapy. The median follow-up duration for the remaining patients was 13.5 months (range 6–31 months). As of August 2025, no patient showed evidence of active disease on imaging. Conclusions: BOTTs are a well-documented phenomenon, but the concept of BOLNs in testicular cancer, with spontaneous regression observed in retroperitoneal or mediastinal lymphadenopathy without systemic chemotherapy has not been previously described, making this the first case series on the subject.It is important to recognize this entity in order to guide the most appropriate treatment strategy and avoid overtreatment. In case of complete lymph node regression and normalization of tumor markers (if initially elevated), close surveillance with thoracoabdominopelvic CT scans and serum marker testing is indicated. In case of partial regression, a biopsy is necessary to determine whether viable tumor cells remain. If the biopsy is inconclusive, a lymph node dissection may be warranted. Management should be tailored based on pathology, imaging evolution, and tumor marker dynamics.
Pierre et al. (Thu,) studied this question.