Nucleolar Organizer Region Count, PCNA and Ki-67 Indices are Diagnostic Markers of Malignancy and Cell Proliferation Rate in Bovine Lymphosarcoma

Lymphoid tumors comprise one of the most common groups of tumors in domestic animals. Lymphosarcoma is expressed as a specific multicentric form in calvesupto six months of age (sporadic) and in adult cattle (enzootic); and as thymic form in young cattle. Eight calves of both sexes aged below six months were necropsied in the department of veterinary Pathology, college of Veterinary Science, Tirupati. During necropsy impression smears, represented tissue samples were collected for Cytopathology, histopathology, AgNOR count and immunohistochemical studies. Cytological smears revealed lymphocytes, prolymphocytes and lymphoblasts with anaplastic changes. Histopathologically, partial to complete obliteration of architecture due to the replacement of normal tissue by lymphoblastic cells in lymphnodes and other visceral organs. The mean AgNOR count of the lymphosarcoma was 4.25 and it appear as a round to irregular, dark brown to black dots of varying sizes in the nuclei. Positive expression of PCNA and Ki67 was noticed in lymphnode, liver, kidney and lung was observed. The labeling index of PCNA and Ki-67 expression and distribution of immunopositive cells may be helpful in the early diagnosis and prognosis of malignant tumors. Hence, AgNOR, PCNA and Ki-67 indices can be used as reliable markers of cell proliferation and malignancy.