Evaluation of collagen in canine tumours using picrosirius red staining

The collagenous tissue in the stroma gives strength to a tumour by giving a skeleton to the tumour cells, thus playing a vital role in tumour progression. In the present study, pattern of collagen distribution in spontaneous canine tumours was studied using picrosirius red stain and then examining under polarizing microscope. Immunohistochemical expression of PCNA was also studied. The PCNA index was minimum for mast cell tumour (25.0) and maximum for complex adenocarcinoma (70.0). Among different canine tumours, in fibroma immature collagen was predominant with moderate amount of mature fibres. Fibrosarcoma, carcinoma of hepatoid gland and mast cell tumour showed predominantly the presence of mature collagen and slight amount of immature collagen. In carcinosarcoma and complex adenocarcinoma, mature collagen was predominant although immature collagen was present in moderate amount. Osteosarcoma showed presence of both mature and immature fibres in high amount.