Glioblastoma, -Wild Type With Fusion: When Morphology May Reliably Predict the Molecular Profile of a Tumor. A Case Report and Literature Review.

It has been reported that in-frame fusions confer to glioblastomas, -wild type (GBMs, wt) some unusual morphologic features, including monomorphous rounded cells with ovoid nuclei, nuclear palisading, endocrinoid network of "chicken-wire" vessels, microcalcifications and desmoplastic stroma, whose observation may predict the molecular profile of the tumor. We herein present a case of recurrent GBMs, wt, exhibiting some of the above-mentioned morphological features and a molecularly-proven fusion. A 56-year-old man presented to our hospital for a recurrent GBM, wt, surgically treated at another center. Histologically, the tumor, in addition to the conventional GBM morphology, exhibited the following peculiar morphologic features: (1) monomorphous neoplastic cells with rounded nuclei and scant pale cytoplasm; (2) thin capillary-like vessels with "chicken-wire" pattern; (3) nuclear palisading; (4) formation of vague perivascular pseudorosettes; (5) spindled tumor cells embedded in a loose, myxoid background. Based on this unusual morphology, molecular analyses were performed and an exon17- exon 10 fusion was found. The present case contributes to widening the morphologic spectrum of -fused GBM, IDHwt and emphasizes that pathologists, in the presence of a GBM, wt with unconventional morphology, should promptly search for this fusion gene.