Polymorphous low-grade neuroepithelial tumor of the young

The patient underwent resection of the temporal lesion. Imaging and pathological features confirmed the diagnosis of a polymorphous low-grade neuroepithelial tumor of the young (PLNTY).

Pathology report

Tumor fragments contain only occasional microcalcifications and are composed of cells with mildly pleomorphic oval nuclei and small to indistinguishable nucleoli. A number of these cells demonstrate intranuclear inclusions. There is vacuolation of the background fibrillary cytoplasm with microcystic change. Probable macrocystic change is also present with scattered hemosiderin laden macrophages in the adjacent tumor. There are readily identifiable entrapped neurons, none of which show dysmorphic features. No specific glioneuronal elements typical of DNETs are identified in the tissue examined. A delicate vascular pattern is present and demonstrates no evidence of endothelial proliferation. There is no necrosis and mitoses are not seen.

There are no high-grade features and no evidence of malignancy.

Immunohistochemical stains:

• GFAP: positive, particularly in plump spindled cells in areas of dense microcalcification, with diffuse staining of cortex and white matter, and some staining of cells with oligodendroglial appearance
• Synaptophysin: essentially negative with weak staining of oligodendroglial-like cells and highlighting infiltrated neural tissue
• NF-κB: negative, demonstrating infiltrated neural tissue
• NeuN: patchy weak staining of nodular areas of tumor cells
• S100: positive nuclear and cytoplasmic staining of tumor cells
• CD34: positive in lesional cells, except in areas of extensive microcalcification. This stain also demonstrates an extensive, blush-type pattern in the adjacent abnormal cortex and white matter, highlighting nodular areas
• Ki67: rare positive nuclei, consistent with <1%. 
• 1p19q codeletion not detected
• IDH1 negative
• BRAF mutant