Tumors harboring CIC-NUTM1 fusion are a newly recognized rare sarcoma, but the documented cases are still limited. It is unclear whether it is the same as classic CIC-DUX4 sarcoma in terms of its clinical, pathologic, and behavioral aspects.
To further explore the clinicopathologic characteristics of CIC-NUTM1 sarcoma.
The cases were diagnosed based on immunophenotype, next-generation sequencing, and fluorescence in situ hybridization tests and compared with the reported CIC-NUTM1 sarcomas in the literature.
Three cases of CIC-NUTM1 sarcomas involving the spine in adults were described. They were 2 men and 1 woman, aged 38 to 61 years. Two tumors were located in thoracic vertebrae and 1 in a cervical vertebra. All were locally advanced lesions destroying the bone and soft tissues without spinal cord involvement or metastasis. The tumors were composed of monomorphic small to medium-sized cells with round to epithelioid appearance. The architecture was lobulated and solid with diffuse or multifocal myxoid stroma. Next-generation sequencing revealed an in-frame fusion between CIC (exon 16 or 17) and NUTM1 (exon 5 or 6) in 3 cases. Fluorescence in situ hybridization confirmed CIC and NUTM1 breaks, and immunohistochemistry showed NUT staining in the nucleus. The patients died of disease 8 to 15 months (mean, 10.7 months) after presentation. Of the CIC-NUTM1 sarcomas reported in the literature along with our cases (n = 11), 8 cases developed in axial bone (5 spine, 3 skull base).
CIC-NUTM1 sarcomas showed distinct anatomic tropism for the axial skeleton and unfavorable behavior compared with classic CIC sarcoma.
The authors have no relevant financial interest in the products or companies described in this article.