A case of GLI1-altered mesenchymal pleural tumour with novel gene fusion: a clinical perspective.

This report presents a case of a Glioma-associated homologue-1 (GLI1)-altered mesenchymal tumour with novel gene fusion arising from the pleura in a 25-year-old female undergoing treatment for primary colorectal adenocarcinoma. A pleural nodule was incidentally detected during staging, and biopsy revealed a mesenchymal tumour with a novel NCOR2(exon 7)::GLI1(exon 6) gene fusion. The tumour showed an indolent course over 10 months of surveillance during chemotherapy, with no significant growth. Despite the absence of malignant features, such as high mitotic rate, necrosis, or large size, and a low proliferation index, surgical excision was chosen due to the rarity and uncertain prognosis of this fusion. Histology confirmed a low-grade tumour with unusual SOX10 expression. This case expands the understanding of GLI1-altered mesenchymal tumours, especially in uncommon sites like the pleura, and highlights the importance of multidisciplinary decision-making. Ongoing molecular and pathological analysis is critical to establish robust diagnostic and prognostic frameworks for such rare tumour entities.