Extraskeletal myxoid chondrosarcoma in pineal region

Abstract

Objective To report the diagnosis and treatment of a case of extraskeletal myxoid chondrosarcoma (EMC) in the pineal region misdiagnosed as chordoid glioma of the third ventricle, and to summarize the clinicopathological features, diagnosis and differential diagnosis of this rare tumor. Methods and Results A 42⁃year⁃old male patient with head MRI showed a space⁃occupying lesion in the pineal region and moderate enhancement on enhanced scan. After the first surgery, the histological morphology showed the boundary between tumor and brain tissue was not clear, spindle or stellate tumor cells were bunched, braided or scattered, the nuclei were small and deeply stained, and the interstitium was rich in collagen fibers and a large number of basophilic myxoid matrix. Immunohistochemical staining showed vimentin (Vim) expression in the cytoplasm of tumor cells, some of which expressed glial fibrillary acid protein (GFAP), CD34, CD99, but not cytokeratin (CK), epithelial membrane antigen (EMA) and S⁃100 protein (S⁃100). The pathological diagnosis was "chordoid glioma of the third ventricle". The tumor recurred 7 months after the first surgery, and the histological morphology of the second surgery showed obvious epithelioid features of the tumor cells, which were arranged in a cord, bundle or braided shape, with enlarged nuclei and easy to see mitotic images (up to 8/10 high magnification field). Some tumor cells were rich in cytoplasm and nuclear deviation, which were rhabdoid. The immunophenotype was the same as before, maintaining the diagnosis of "notochord glioma". The patient died of tumor progression 5 months after the second surgery. Combined with the literature, supplemental immunohistochemical staining showed that the tumor cells did not express Brachyury, thyroid transcription factor 1 (TTF⁃1), and SMARCB1/INI⁃1 proteins. Fluorescence in situ hybridization (FISH) test was positive for NR4A3 (9q22.33) gene rupture, and finally confirmed the diagnosis of EMC. Conclusions EMC in the pineal region is extremely rare, and attention should be paid to distinguishing it from the frequent mucinous tumors in the pineal region, such as chordoma, chordoid meningioma and chordoid glioma. Definite diagnosis depends on histological morphology, immunohistochemical staining and molecular detection.

doi：10.3969/j.issn.1672⁃6731.2022.12.010