GLI1-Altered Mesenchymal Tumor with ACTB Fusion and Somatostatin Receptor 2A (SSTR2A) Immunopositivity

Glioma-associated oncogene (GLI1)-altered mesenchymal tumors are a newly described entity of neoplasms with very few case reports published in the literature. GLI1-altered neoplasms have a moderate degree of variability as they are seen in a broad range of anatomic sites and amongst people of all ages. A common feature that most GLI1-altered tumors share is the histologic makeup of monomorphic ovoid cells organized in distinct nests and an arborizing vascular blood supply. While previously thought to be benign entities, more recent studies have highlighted metastatic potential within this group of tumors, further emphasizing the variability within this class of disease and the necessity to further understand the behavior of these tumors. Here, we report a 36-year-old male presenting with a palpable mass centered within the right gluteus maximus muscle. The mass was excised and measured 6.3 cm in the greatest dimension, with histologic findings and molecular workup confirming the diagnosis of a GLI1-altered mesenchymal tumor with beta-acting gene (ACTB) fusion. Interestingly, the tumor stained positive for somatostatin receptor 2A (SSTR2A), a stain that has yet to be elucidated as a potential diagnostic tool for this rare entity.