Focal cortical dysplasia is a frequent coexistent pathology in patients with Rasmussen's encephalitis.

INTRODUCTION: Rasmussen's encephalitis (RE) is a rare, predominantly pediatric epilepsy disorder of unknown etiology. It classically affects one of the cerebral hemispheres and histologically shows cortical chronic inflammation, gliosis, and neuronal loss. The etiopathogenesis of RE remains unknown, with genetic, infectious, and autoimmune factors all speculated to play a role. Although the histologic findings in RE are well described, few studies have investigated a large cohort of cases looking for the coexistence of RE with focal cortical dysplasia (FCD). DESIGN: The study is a retrospective review of RE patients who underwent surgical resection of brain tissue between 1979 and 2021. Relevant patient history was retrieved, and available histologic slides were reviewed. The histologic severity of RE was described according to the Pardo criteria. In cases where FCD was present, the observed patterns of FCD (namely Ia, Ib, IIa, IIb, etc.) were described using the International League Against Epilepsy (ILAE) classification. RESULTS: Thirty-eight resection specimens from 31 patients formed the study cohort. Seventeen patients (54.8 %) were male; average age at surgery was 8 years (range: 2-28 years). Twenty-seven resection specimens (71.1 %) from 23 patients (74 %) showed evidence of coexistent FCD. Most cases with FCD resembled the ILAE type Ib (n = 23) pattern. Cases of RE that did not show FCD were either Pardo stage 1 (n = 5) or 4 (n = 6), with all Pardo stage 2 and 3 cases demonstrating FCD. CONCLUSIONS: FCD was found in most patients with RE (74 %). The most observed pattern of FCD was ILAE Ib.

Tumor-to-tumor metastasis of an adenocarcinoma to a glioblastoma with review of the literature on tumor-to-tumor metastasis to gliomas.

Tumor-to-tumor metastasis (TTM) is a process where one tumor metastasizes to another tumor. It is an exceedingly rare phenomenon, particularly in the central nervous system, where it most commonly occurs with meningiomas as the recipient. Herein, we present a case of tumor-to-tumor metastasis of an adenocarcinoma to a glioblastoma in a 75-year-old female. The patient had a history of high-grade ductal carcinoma in situ of the breast 8 years prior, treated with lumpectomy and radiation. She presented with a left fronto-parietal mass. Histologically, the lesion showed a glioblastoma, IDH-wildtype, WHO grade 4, associated with a metastatic adenocarcinoma (positive for estrogen receptor, progesterone receptor, and mammaglobin), suggesting a breast primary. The patient passed away 5 months after surgery. Involvement of glioblastoma by TTM is especially rare; only 1 case of TTM to glioblastoma is thus far reported in the English literature. The mechanism by which TTM occurs is poorly understood. TTM may be the first presentation of an occult malignancy and warrants thorough clinical, laboratory, and imaging investigation.