Cytological, Histopathological and Immunohistochemical Studies on Naturally Occurring Cutaneous Melanomas in Cattle in and Around Namakkal, Tamil Nadu, India

Background: Melanomas are tumours that originate from melanoblasts. The studies on bovine tumours are of clinical concern since some melanocytic tumours are congenital and occur in young animals. The present work was carried out to study the pathomorphological characteristics of melanomas in cattle for early diagnosis and intervention. Methods: Tumour samples were collected from suspected cases of neoplasia from four animals during the study period. Data pertaining to the animals were collected. Fine needle aspiration cytology and impression smear were stained with Giemsa stain. Tissue samples were collected in 10 per cent neutral buffered formalin for histopathological examination. Special staining with Fontana silver stain and immunohistochemistry with Melan- A and S- 100 markers for confirmatory diagnosis of melanin pigment was done. Result: Cytology revealed neoplastic cells with vacuolation and pleomorphism. Cytoplasm contained abundant melanin pigments. Microscopically, the cytoplasm contained abundant brown, black coloured melanin pigment granules. Tissue sections stained with Fontana silver impregnation method revealed the presence of black coloured granules. Immunohistochemistry with Melan-A and S-100 revealed strong expression of brown coloured reaction in the cytoplasm of the neoplastic cells.