Pathogenic alterations, namely, fusions and amplifications, of the GLI1 gene have been identified in various mesenchymal tumors, including pericytoma with t(7;12), plexiform fibromyxoma, gastroblastoma, and other malignant mesenchymal neoplasms arising in the soft tissues, as well as in various visceral organs. However, only three cases of GLI1-rearranged renal tumors have been reported to date, comprising two low-grade spindle cell tumors with GLI1::FOXO4 fusion along with one GLI1-rearranged case with an unknown fusion partner. In this study, we analyzed three cases with GLI1::FOXO4 fusion and overlapping morphology. One of the cases was reported previously, but an extended clinical and immunohistochemical information is provided. The studied cases occurred in 2 female and 1 male patients aged 35, 55, and 62 years (mean 51 years). All three tumors affected the renal parenchyma and grew as unencapsulated but well-circumscribed solid masses containing occasional entrapped and dilated renal tubules. The tumor cells were organized in cords, nests, or fascicles, had a round to spindled shape, and exhibited only mild nuclear atypia and minimal mitotic activity. They had a sparse eosinophilic to clear cytoplasm and were embedded in myxocollagenous stroma. Immunohistochemically, all cases expressed GLI1 (albeit with variable intensity) and harbored GLI1::FOXO4 fusion. All three patients were treated solely by complete surgical excision. Case 1 was alive with unknown disease status, case 2 was alive without evidence of disease, and case 3 died of unrelated causes. Our study doubles the number of reported cases with GLI1::FOXO4 fusion. The so far absolute predilection of this fusion for renal tumors, coupled with the absence of reports of other GLI1 fusions in tumors of the kidney, might indicate the potential existence of a distinct renal subtype with morphological features similar to other GLI1-altered tumors. All four reported cases had an uneventful follow-up which, together with their low-grade morphological features, suggests that these tumors might have a favorable prognosis.

• Keywords
• GLI1::FOXO4 fusion, GLI1-altered tumors, Kidney, Soft tissue,
• MeSH
• Adult MeSH
• Forkhead Transcription Factors * genetics   MeSH
• Gene Rearrangement * MeSH
• Immunohistochemistry MeSH
• Middle Aged MeSH
• Humans MeSH
• Biomarkers, Tumor * genetics   analysis   MeSH
• Kidney Neoplasms * genetics   pathology   MeSH
• Zinc Finger Protein GLI1 * genetics   MeSH
• Cell Cycle Proteins * genetics   MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Case Reports MeSH
• Names of Substances
• Forkhead Transcription Factors * MeSH
• FOXO4 protein, human MeSH Browser
• GLI1 protein, human MeSH Browser
• Biomarkers, Tumor * MeSH
• Zinc Finger Protein GLI1 * MeSH
• Cell Cycle Proteins * MeSH

GLI1 -altered mesenchymal tumor is a recently described distinct pathologic entity with an established risk of malignancy, being defined molecularly by either GLI1 gene fusions or amplifications. The clinicopathologic overlap of tumors driven by the 2 seemingly distinct mechanisms of GLI1 activation is still emerging. Herein, we report the largest series of molecularly confirmed GLI1 -altered mesenchymal neoplasms to date, including 23 GLI1- amplified and 15 GLI1 -rearranged new cases, and perform a comparative clinicopathologic, genomic, and survival investigation. GLI1- rearranged tumors occurred in younger patients (42 vs. 52 y) and were larger compared with GLI1 -amplified tumors (5.6 cm vs. 1.5 cm, respectively). Histologic features were overall similar between the 2 groups, showing a multinodular pattern and a nested architecture of epithelioid, and less commonly spindle cells, surrounded by a rich capillary network. A distinct whorling pattern was noted among 3 GLI1 -amplified tumors. Scattered pleomorphic giant cells were rarely seen in both groups. The immunoprofile showed consistent expression of CD56, with variable S100, CD10 and SMA expression. Genomically, both groups had overall low mutation burdens, with rare TP53 mutations seen only in GLI1- amplified tumors. GLI1 -amplified mesenchymal tumors exhibit mostly a single amplicon at the 12q13-15 locus, compared with dedifferentiated liposarcoma, which showed a 2-peak amplification centered around CDK4 (12q14.1) and MDM2 (12q15). GLI1 -amplified tumors had a significantly higher GLI1 mRNA expression compared with GLI1 -rearranged tumors. Survival pooled analysis of current and published cases (n=83) showed a worse overall survival in GLI1 -amplified patients, with 16% succumbing to disease compared with 1.7% in the GLI1- rearranged group. Despite comparable progression rates, GLI1 -amplified tumors had a shorter median progression-free survival compared with GLI1 -rearranged tumors (25 mo vs. 77 mo). Univariate analysis showed that traditional histologic predictors of malignancy (mitotic count ≥4/10 high-power fields, presence of necrosis, and tumor size ≥5 cm) are associated with worse prognosis among GLI1 -altered mesenchymal tumors.

• MeSH
• Gene Amplification * MeSH
• Time Factors MeSH
• Adult MeSH
• Phenotype MeSH
• Genetic Predisposition to Disease MeSH
• Gene Rearrangement * MeSH
• Middle Aged MeSH
• Humans MeSH
• Adolescent MeSH
• Young Adult MeSH
• Biomarkers, Tumor * genetics   MeSH
• Soft Tissue Neoplasms genetics   pathology   mortality   MeSH
• Zinc Finger Protein GLI1 * genetics   MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Adolescent MeSH
• Young Adult MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Comparative Study MeSH
• Names of Substances
• GLI1 protein, human MeSH Browser
• Biomarkers, Tumor * MeSH
• Zinc Finger Protein GLI1 * MeSH

Classification of tumors of the head and neck has evolved in recent decades including a widespread application of molecular testing in tumors of the sinonasal tract, salivary glands, and soft tissues with a predilection for the head and neck. The availability of new molecular techniques has allowed for the definition of multiple novel tumor types unique to head and neck sites. Moreover, an expanding spectrum of immunohistochemical markers specific to genetic alterations facilitates rapid identification of diagnostic molecular abnormalities. As such, it is currently possible for head and neck pathologists to benefit from a molecularly defined tumor classification while making diagnoses that are still based largely on histopathology and immunohistochemistry. This review covers the principal molecular alterations in sinonasal malignancies, such as alterations in DEK, AFF2, NUTM1, IDH1-2, and SWI/SNF genes in particular, that are important from a practical standpoint for diagnosis, prognosis, and prediction of response to treatment.

• Keywords
• Head and neck, Molecular diagnostics, Next-generation sequencing, Sinonasal, Sinonasal tumor, Soft tissue,
• MeSH
• Humans MeSH
• Biomarkers, Tumor * genetics   analysis   MeSH
• Paranasal Sinus Neoplasms * pathology   genetics   classification   diagnosis   MeSH
• World Health Organization MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Biomarkers, Tumor * MeSH