MMP2 and neoplasm: To further our evaluation of the potential presence of tumor within these 7 HSNs, we additionally examined the expression of genes characteristic of tumor microenvironments including the following: desmoplasia (dense fibrosis around a neoplasm) genes, including those pertaining to the collagen (COL6A1, COL6A2, COL1A2, COL1A1); neutrophil/myeloid-derived suppressor cell infiltration (CXCR1, CXCR2); cell proliferation (MYC, CDK4) and tumor invasion (MMP2, MMP9, MM14), (Additional file 1: Figure S6a-d).