Granulomatous inflammation in pineal germinoma. A cause of diagnostic failure at stereotaxic brain biopsy.

We report four patients with pineal germinoma in whom the initial procedure for obtaining a tissue diagnosis was a stereotaxic biopsy. In all four cases, the biopsy showed granulomatous inflammation with epithelioid cells and lymphocytes. In one case, the granulomatous inflammation was accompanied by classical germinoma. Another case exhibited malignant cells considered nondiagnostic for a specific neoplasm. Two cases had no evidence of a malignant tumor; they were composed entirely of granulomatous inflammation. In two of the three cases where the diagnosis was not established by the first biopsy, a second stereotaxic biopsy showed pineal germinoma. Tissue obtained at resection in the third patient revealed large areas of granulomatous inflammation accompanying the germinoma. Immunoperoxidase stains for ferritin and placental alkaline phosphatase did not increase diagnostic yield. We conclude that a finding of granulomatous inflammation in a stereotaxic biopsy specimen of a pineal mass should suggest a diagnosis of germinoma, followed by sampling from several different target points within the lesion.