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.

• Klíčová slova
• GLI1::FOXO4 fusion, GLI1-altered tumors, Kidney, Soft tissue,
• MeSH
• dospělí MeSH
• forkhead transkripční faktory * genetika   MeSH
• genová přestavba * MeSH
• imunohistochemie MeSH
• lidé středního věku MeSH
• lidé MeSH
• nádorové biomarkery * genetika   analýza   MeSH
• nádory ledvin * genetika   patologie   MeSH
• protein Gli1 * genetika   MeSH
• proteiny buněčného cyklu * genetika   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH
• Názvy látek
• forkhead transkripční faktory * MeSH
• FOXO4 protein, human MeSH Prohlížeč
• GLI1 protein, human MeSH Prohlížeč
• nádorové biomarkery * MeSH
• protein Gli1 * MeSH
• proteiny buněčného cyklu * 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
• amplifikace genu * MeSH
• časové faktory MeSH
• dospělí MeSH
• fenotyp MeSH
• genetická predispozice k nemoci MeSH
• genová přestavba * MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• nádorové biomarkery * genetika   MeSH
• nádory měkkých tkání genetika   patologie   mortalita   MeSH
• protein Gli1 * genetika   MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH
• Názvy látek
• GLI1 protein, human MeSH Prohlížeč
• nádorové biomarkery * MeSH
• protein Gli1 * MeSH

Mesenchymal neoplasms with GLI1 alterations have recently been reported in several anatomic locations. Their morphology and immunohistochemistry (IHC) are nonspecific, making their recognition a true challenge. To assess the diagnostic value of GLI1 and p16 IHC for identifying GLI1-altered neoplasms, we evaluated 12 such neoplasms (6 GLI1-amplified and 6 with GLI1-fusions) using the GLI1 IHC. Additionally, we evaluated some of their morphological and molecular mimickers, including glomangiomas, Ewing sarcomas (ES), myxoid liposarcomas, and MDM2/CDK4-amplified sarcomas (well-differentiated liposarcoma/WDLPS, dedifferentiated liposarcoma/DDLPS, and intimal sarcoma). All successfully tested GLI1-altered tumors (11/11) demonstrated at least moderate/strong nuclear and/or cytoplasmic GLI1 IHC positivity. GLI1-amplified tumors exhibited a moderate/strong predominantly nuclear staining, compared to a moderate, patchy, and predominantly cytoplasmic GLI1 positivity in GLI1-fusion tumors. Among their mimics, GLI1 immunoreactivity, either cytoplasmic or nuclear, was observed in intimal sarcoma (3/3) and WDLPS/DDLPS (22/25). GLI1 IHC demonstrated 92% sensitivity and 90.8% specificity in diagnosing GLI1-altered neoplasms. Strong/moderate nuclear/cytoplasmic p16 immunoexpression was noted in all GLI1-amplified tumors compared to none of fused cases. Overall, the GLI1/p16 combination demonstrated a sensitivity and specificity of 100% and 93% for GLI1-amplified tumors. In conclusion, we confirm that GLI1 IHC represents a good, quick, and cheap helpful screening tool. The inclusion of p16 may aid in pre-screening for potential GLI1-amplified neoplasms and provide insights on which tumors warrant further molecular testing.

• Klíčová slova
• GLI1-altered neoplasm, GLI1-amplified neoplasms, GLI1 IHC, IHC, Sensitivity, Specificity, p16,
• MeSH
• Ewingův sarkom diagnóza   patologie   MeSH
• glomangiom diagnóza   patologie   MeSH
• imunohistochemie * MeSH
• inhibitor p16 cyklin-dependentní kinasy * metabolismus   analýza   MeSH
• lidé MeSH
• nádorové biomarkery * analýza   metabolismus   genetika   MeSH
• nádory z pojivové a měkké tkáně * diagnóza   patologie   MeSH
• protein Gli1 * analýza   metabolismus   genetika   MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• CDKN2A protein, human MeSH Prohlížeč
• GLI1 protein, human MeSH Prohlížeč
• inhibitor p16 cyklin-dependentní kinasy * MeSH
• nádorové biomarkery * MeSH
• protein Gli1 * MeSH