Comparison of Morphometric Assessment Using Methyl Green Pyronin and AgNOR Staining of Oral Squamous Cell Carcinoma

Oral cancer, a major global health problem holds the sixth position worldwide with a marked variation in its geographic distribution. It is ranked as the third most frequent cancer in the developing world after stomach and cervical cancers. Amongst oral cancers, oral squamous cell carcinoma accounts for over 90% of the cases.

Out of the developing counties, Indo-Pak subcontinent amounts to one third of the global oral cancer burden. Carcinoma of the oral cavity in Pakistan, one of the high-risk countries is the second most frequent cancer in either gender. With differential distribution among sub-populations, it represents 8.8% of all reported cancer cases. The most predominant risk factors include tobacco smoking, betel chewing and alcohol.

Screening and specific diagnostic tools are two innovative approaches for early detection of oral cancer. Conventional oral examination and clinical evaluation remains the foundation of screening approaches whereas surgical biopsy followed by histological analysis is attributed to be the gold standard for diagnosing malignant oral lesions. Furthermore, some adjunctive techniques may contribute to the diagnosis of oral cancer. Of these vital staining, DNA analysis, chemiluminescence, tissue fluorescence, light-based detection systems and biomarkers are now on the forefront.

Biomarkers have been valuable in revealing additional information about tumor pathology, including the inactivation of tumor suppressor genes, angiogenesis, apoptosis and cell proliferation. Aberrations in proliferation kinetics are the most imperative factor during tumor progression. Three main categories of cell proliferation markers include growth fraction markers like Ki67, cycle-specific markers like PCNA(Proliferating Cellular Nuclear Antigen), and cell cycle time markers like AgNOR. During malignancy, proliferation and protein synthesis is mainly controlled by the nucleus.

Nucleolar Organizer Regions (NORs) are loops of DNA on the short arms of acrocentric chromosomes that presumably are associated with cell proliferation. Some of the NOR associated proteins are argyrophilic and can be demonstrated as black dots by the silver staining technique and the structures thus demonstrated are known as AgNORs. The AgNOR quantitative parameters provide information about the velocity of cell proliferation during cell cycle. Neoplastic progression is affected more by the rate of cell proliferation, rather than the proliferative activity per se.