COL1A1-PDGFB gene fusion in dermatofibrosarcoma protuberans: a useful diagnostic tool and clinicopathological analysis.

The PDGFB gene is found at 22q12.3-q13.1, and the COL1A1 gene is located at 17q21.3-q22.1. If the COL1A1 gene of 17q21-22 is fused with the PDGFB gene of 22q13.1, then it forms a new COL1A1-PDGFB fusion gene, one that has been found in dermatofibrosarcoma protuberans (DFSP) and lasts for many years. The expression of PDGFB loses the regulation of upstream inhibitory factors and leads to the mass production of COL1A1-PDGFB chimeric mRNA under the initiation of COL1A1 sequence, a crucial factor in the development of DFSP. In our study, we retrospectively analyzed 2 cases: case 1 is a 25-year-old student with three surgical resections in his right lumbar region. Initially, his diagnosis (from another hospital in 2009) was vascular lymphangioma. When the disease recurred after 6 years, he went to our hospital and the diagnosis was giant cell fibroblastoma (GCF). Molecular pathology (using the fluorescence in situ hybridization, FISH) showed the COL1A1-PDGFB gene fusion, presented as the fusion of 3 or more red and green signals. In 2017, the patient had another recurrence of the disease, and he underwent a third surgical resection. The other case is a 51-year-old woman who had presented with pain in her left lumbosacral, accompanied by left buttock and left thigh numbness for 3 months. The diagnosis was DFSP, which also showed COL1A1-PDGFB gene fusion. Here we review the clinicopathologic features and differential diagnosis of this rare tumor, so that it can be better recognized.