ORIGINAL ARTICLE Oral Pathology Actual proliferating index in oral squamous cell carcinoma and leukoplakia Abhay R. Chandak 1 , Amol Ramchandra Gadbail 2 , Minal S. Chaudhary 2 , Shweta A. Chandak 3 & Ritesh Wadhwani 4 1 Department of Oral and Maxillofacial Pathology and Microbiology, Swargiya Dadasaheb Kalmegh Smruti Dental College and Hospital, Nagpur, Maharashtra, India 2 Department of Oral and Maxillofacial Pathology and Microbiology, Datta Meghe Institute of Medical Sciences, Sharad Pawar Dental College and Hospital, Sawangi (Meghe), Wardha, Maharashtra, India 3 Department of Pediatric and Preventive Dentistry, Swargiya Dadasaheb Kalmegh Smruti Dental College and Hospital, Nagpur, Maharashtra, India 4 Department of Oral and Maxillofacial Pathology and Microbiology, Jamanlal Goenka Dental College and Hospital, Akola, Maharashtra, India Introduction Oral cancer holds eighth position in cancer incidence worldwide. A geographic variation in the incidence of oral squamous cell carcinoma (OSCC) exists. In India, OSCC ranks first among all cancers in males, and third in females. Incidence rates vary from seven to 17/100 000 people annually. Based on cancer registry data, it is esti- mated that 75 000–80 000 new cancer cases develop annually in India. 1 Squamous cell carcinoma is the most common malig- nant neoplasm of the oral cavity, accounting for more than 90% of all oral malignancies. It is usually preceded by premalignant lesions. The identification of these premalignant lesions through clinical, morphological, and molecular means helps in the early detection and treat- ment of OSCC. Leukoplakia is the most common oral premalignant lesion. 2 Oral premalignant lesions are known to represent an increased risk of oral cancer devel- opment, with quoted malignant transformation rates Keywords actual proliferation index, argyrophilic nucleolar organizer region count, Ki-67 labeling index, oral premalignant lesion, oral squamous cell carcinoma. Correspondence Dr Amol Ramchandra Gadbail, Department of Oral and Maxillofacial Pathology and Microbiology, Datta Meghe Institute of Medical Sciences, Sharad Pawar Dental College and Hospital, Sawangi (Meghe), Wardha 442001, Maharashtra, India. Tel: +91-97661-35691 Fax: +91-071-5228-7713 Email: gadbail@yahoo.co.in Received 27 December 2010; accepted 29 January 2011. doi: 10.1111/j.2041-1626.2011.00057.x Abstract Aim: To examine the possible association between epithelial proliferation and disease progression in the oral mucosa using the actual proliferation index. Methods: The actual proliferation index was measured by the Ki-67 labeling index and argyrophilic nucleolar organizer region count per nucleus. Immuno- histochemistry was carried out for Ki-67 by using the molecular immunology borstel-1 clone in 20 leukoplakias, 20 oral squamous cell carcinomas, and 10 normal oral mucosae. Results: The argyrophilic nucleolar organizer region count per nucleus, Ki-67 labeling index, and actual proliferation index were significantly higher in oral squamous cell carcinoma, followed by leukoplakia and normal oral mucosa. Leukoplakia with dysplasia showed a significantly higher Ki-67 labeling index and actual proliferation index, compared to leukoplakia without dysphasia. There was a significant correlation of Bryne’s histological malignancy grading with the argyrophilic nucleolar organizer region count and the Ki-67 labeling index. There was a significant positive correlation between the argyrophilic nucleolar organizer region count and the Ki-67 labeling index among all groups. Conclusions: Leukoplakia or suspected epithelial dysplasia should be stained for argyrophilic nucleolar organizer regions and Ki-67. The actual proliferation index is not only useful as a prognostic factor, but could also be a promising treatment determining modality for patients with premalignant and malignant lesions. Journal of Investigative and Clinical Dentistry (2011), 2, 176–183 176 ª 2011 Blackwell Publishing Asia Pty Ltd