Primary CNS lymphoma: Survival after craniotomy with resection versus stereotactic biopsy and the clinical impact of the "vanishing tumor" phenomenon.

OBJECTIVE: Primary central nervous system lymphoma (PCNSL) is a rare malignancy in which neurosurgical management is usually limited to stereotactic biopsy, while resection is considered in selected cases. Pre-diagnostic corticosteroids may cause radiological regression ("vanishing tumor"), potentially delaying diagnosis and treatment. METHODS: We conducted a single-center retrospective cohort study of adults (≥18 years) with histopathologically confirmed PCNSL treated between January 2015 and April 2023 at the Institute of Psychiatry and Neurology (Warsaw). Patients were grouped by neurosurgical strategy (stereotactic biopsy vs craniotomy with resection). Vanishing tumor was defined as marked radiological reduction prior to histopathological confirmation. Diagnostic interval was defined as time from index hospital admission to neuropathological diagnosis. Overall survival (OS) was calculated from index hospital admission to death or last contact and analyzed using Kaplan-Meier estimates and log-rank tests. RESULTS: Fifty-six patients were included (mean age 66 years, range 23-82); 40 (71%) underwent biopsy and 16 (29%) resection. Median OS was longer after resection than biopsy (465 vs 149.5 days; log-rank p = 0.029). Vanishing tumor occurred in 12 patients (21%) and was associated with a longer diagnostic interval (median 82 vs 9 days; p < 0.001). Median OS was shorter in patients with vanishing tumor (149.5 vs 356 days), but the difference was not significant (p = 0.313). CONCLUSIONS: In selected, surgically accessible PCNSL cases, resection was associated with longer OS than stereotactic biopsy, although residual confounding cannot be excluded. Vanishing tumor was common and associated with substantial diagnostic delay; corticosteroids should be restricted to clear clinical necessity in suspected PCNSL.