Clear-cell renal cell carcinoma and glioblastoma multiforme coexistence: Double primary malignancy, does it have a causal relationship?

Background: Multiple primary malignancies (MPMs), especially coexistence of renal cell carcinoma (RCC) and glioblastoma multiforme (GBM), are rare. The most likely clinical diagnosis in patient with tumor in another organ is metastatic brain tumor. Although GBM is the most common brain tumor, it is rarely coexistent with other malignancies. Case Description: A 64-year-old female presented with headache and dizziness, along with abdominal pain for 2 weeks before being admitted. The abdominal computed tomography (CT) scan showed a kidney tumor. The patient developed left hemiplegia, and the brain CT scan showed an intracranial tumor. The patient suggested for radical nephrectomy and craniotomy tumor removal. Histopathology of the kidney and brain tumor revealed two different features, which showed RCC and GBM. Immunohistochemistry result confirmed the diagnosis of GBM and IDH1 wild type; coexistent with clear cell RCC. Conclusion: The coexistence of carcinoma and glioma should be regarded as coincidental cases if it did not accomplish the criteria for tumor-to-tumor metastasis or proven to be a genetic syndrome. This case report provides an addition to the literature about double primary malignancy in a single patient. More studies are needed to confirm whether they have causal relationship or merely coincidental findings.