• Collision tumor, a metastatic melanoma within a meningioma: a case report
• Tumor-to-tumor metastasis of clear cell renal cell carcinoma to meningioma: illustrative case
• Breast Cancer Metastasis Developed Inside an Angiomatous Meningioma: A Case Report
• Review of metastasis to meningiomas with case examples
• Epithelial differentiation mimicking tumor-to-tumor metastasis in an isocitrate dehydrogenase wild-type glioblastoma
• A Cerebellar Tumor-to-Tumor Metastasis in a Patient With Von Hippel-Lindau Disease
• Glioblastoma with Probable Intratumoral Adenocarcinoma Metastasis: A Rare Report with Review of Literature
• Metastasis infiltrating tumor to meningioma: a case report

Tumor-to-tumor metastasis inside a meningioma

Tumor-to-tumor metastasis (TTM) is defined as the hematogenous metastasis within a primary host tumor from a donor neoplasm. Although the precise mechanism of TTM is still unclear, it has been reported in the literature for over a century ¹⁾

There is a difference between Tumor-to-tumor metastasis and collision tumors. The former implies a recipient role of the host tumor, and the latter refers to a co-localization of two different tumors that grow into one another, both being in the same organ. Tumor-to-tumor brain metastasis is a well-described phenomenon but with unclear pathophysiology. Deeper knowledge could be beneficial for its management ²⁾.

lung cancer and breast cancer are the most common donor tumors in TTM ^{3) 4) 5)}.