Eosinophilic inclusions in ependymoma represent microlumina: a light and electron microscopic study

Abstract

A study was undertaken to determine the pathological significance of previously unrecognized intracytoplasmic eosinophilic inclusions (IEIs) in ependymoma. The study group consisted of 58 ependymomas, all of which were pathologically characterized and graded according to the 1993 WHO classification. Electron microscopic studies were performed in 16 cases. The study showed that 33 (57%) ependymomas had IEIs and that in 8 cases these were abundant. Round and eosinophilic, their sizes varied from 10 microns to a tiny dot. Similar eosinophilic bodies were also observed between tumor cells. The inclusions were weakly PAS positive. On immunostains, IEIs were frequently positive for glial fibrillary acidic protein, less often for S-100 protein, and for epithelial membrane protein and CAM 5.2. They were negative for AE1/AE3, carcinoembryonic antigen and Ber-EP4. Ultrastructurally, IEIs represented intracytoplasmic lumens containing microvilli and cilia. These microlumina also frequently contained granulo-tubular materials. With reference to tumor subtypes, IEIs occurred most frequently in ordinary and clear cell ependymomas. IEIs were also present in 4 of 6 anaplastic ependymomas studied. In conclusion, IEIs represent microlumina and occur in more than a half of ependymomas including malignant examples. Their finding is a helpful diagnostic feature of ependymoma.

Highly anaplastic extraventricular ependymoma arising in an adult, mimicking metastatic adenocarcinoma with heavy stromal inflammation and emperiporesis

“…They conform to microlumens with microvilli and cilia recognized ultrastructurally, representing the epithelial differentiation of ependymomas. The eosinophilic inclusions are frequently positive for GFAP, and less often for EMA 15 . A few eosinophilic inclusions detected in the recurrent tumor of the present case were also positive for EMA with autoclave pretreatment.…”

History of allergies among adults with glioma and controls

“…It is intriguing in this context to note the apparent efficacy of T‐helper 2 cytokines IL‐4 and Il‐13 in inducing antiglioma response in animal models 31–33. IL‐4 also induces recruitment of eosinophils and macrophages to tumor sites, inducing tumor cell death and formation of microlumina, or high endothelial venules, which allows further immune response against tumor‐derived antigens 34, 35. The exact nature of what constitutes “protective” immune function against brain cancer and how this might be exploited for therapeutic and preventative measures warrant further study.…”

Intramedullary Clear Cell Ependymoma in the Thoracic Spinal Cord: A Case with Its Crush Smear and Ultrastructural Findings

“…Here, we carefully examined ultrastructural details to find different features of clear cell ependymoma from classic ependymoma. Intracytoplasmic lumen is one of the histological characteristics and ultrastructural feature of ependymoma that corresponded to microlumina with or without microvilli-lining under electron microscopy (8). Regardless of the type of ependymoma, the intracytoplasmic lumen is one of the common findings.…”

“…Regardless of the type of ependymoma, the intracytoplasmic lumen is one of the common findings. One case frequently containing granulo-tubular materials has been reported, which were regarded as degraded microvilli of the tumor cells (8). …”