Their presence in collagen-rich regions raised a critical challenge: how to reliably distinguish tumor from stroma when FOXL2 and other tumor-associated markers are also detected in COL1A1+ areas, or how to differentiate COL1A1+ fibromatous tumor tissue from stromal regions containing FOXL2+ stromal elements (both classified as FOXL2+COL1A1+). The gene discussed is COL1A1; the disease is neoplasm.