Evaluation of Proliferative Marker Ki-67 in Adenoid Cystic Carcinoma: A Retrospective Study

Abstract

Adenoid cystic carcinoma (ACC) is a malignant tumor of salivary gland origin. Although the histologic appearance of ACC is low grade, management of this malignancy is a distinct therapeutic challenge because of its tendency for perineural involvement and potential for distant metastasis. Ki-67 antigen is expressed during the G1, S, G2 and M phases in the cell cycle but is absent in the quiescent G0 phase in tissue sections. Aim of the study was to review hematoxylin and eosin stained slides in order to confirm the previous histopathological diagnosis as per the criteria given by World Health Organisation (WHO) and to evaluate the expression of cell proliferation marker, Ki-67 antigen in Adenoid cystic carcinoma and correlate the expression of Ki-67 antigen histopathologically with different grades in Adenoid cystic carcinoma. Tissue samples of 32 cases (12 males and 20 females) were selected from minor salivary glands with age range from 21 to 70 years. Two paraffin-embedded sections of these total 32 cases each of 4 µm thick were cut on a rotary microtome. One section was stained using hematoxylin and Eosin (H&E) and the other was used for Immunohistochemical staining with Ki-67 antigen. Among these 32 cases of Adenoid cystic carcinoma, Histologically 14 (43.75%) tumors were classified in grade I, 8 (25%) were in grade II, and 10 (31.25%) were in grade III. The average percentage of Ki-67 expression was 27.12% in grade I, 34.43% in grade II and 38.45% in grade III. Ki-67 immunoreactivity increased with increase in histopathological grades of ACC. Since Ki-67 is a useful marker for assessing the proliferative potential of tumors, the prognosis of patients can definitely be predicted.