A Comparative Report on Intracranial Tumor-to-Tumor Metastasis and Collision Tumors

The incidence of 2 distinct tumor types occupying the same anatomic location is rarely observed and may be accounted for by 2 separate mechanisms: tumor-to-tumor metastasis and collision tumors, where 2 adjacent tumors invade one another. These rare phenomena arise from distinct mechanisms, which may affect their preoperative recognition, surgical approach, and postoperative care. We review 2 cases, highlighting their identification and perioperative management. In case 1, a 71-year-old patient with a history of sphenoid wing meningioma presented with headache, nausea, and vomiting and was found to have a mass with meningioma and glioblastoma (GBM) characteristics. In case 2, a 61-year-old man with worsening dysmetria in the setting of unintentional weight loss presented with multiple masses in the pelvis, abdomen, lung, and brain. The brain masses were classified as meningioma with intratumoral metastatic adenocarcinoma foci. Preoperative recognition of collision tumor and tumor-to-tumor metastasis is imperative for surgical planning, including selecting regions for tissue biopsy and goals of care. Meticulous evaluation of history and imaging and thorough pathologic analysis allow for effective diagnosis and optimal patient outcomes. •Collision tumors represent 2 distinct geographically colocalized tumors growing into one another.•Tumor-to-tumor metastasis involves hematogenous spread of malignancy to the parenchyma of an anatomically distant tumor.•Preoperative identification of these entities aids in surgical planning and successful treatment of these rare tumors.