Characteristics of Collagen to Differentiate Fibrous Hyperplasia from Mesenchymal and Mixed Odontogenic Tumors: A Polarized Microscopic Study

Context: Mesenchymal odontogenic tumors arise from the remnants of the mesenchymal portion of tooth germ. Central odontogenic fibroma (COF), odontogenic myxoma (OM) and Ameloblastic fibroma (AF) are closely related and show varied clinical presentation and overlapping histopathology. They are differentiated by their collagen quantity, maturity and distribution. Diagnostic difficulties are posed when compared with enlarged dental follicle (EDF) as it closely resembles them. Aim: To analyze the collagen in COF, OM, AF and EDF both quantitatively and qualitatively to choose the best attributes which characterize them. Settings and Design: Polarized microscopy and picro-sirius red staining to visualize every collagen bundle in birefringent state was employed. Material and Methods: 22 tissue sections of EDF, COF, OM and AF were studied for mean collagen bundles in 100 μm2 areas, the maturity of 50 bundles each of thin, thick and intermediate sizes and the number of mature, immature and intermediately mature bundles in 100 μm2 irrespective of thickness. Statistical analysis used: ANOVA, Tukey and Scheffe test were used to find the significance. Results: COF showed maximum number of collagen bundles in 100 μm2 area (P value<0.001). For every 50 intermediately thick bundles, the most red were EDF 20(3); the most green were COF 28(7) and the most yellow were OM 23(4). For every 50 thick bundles, the most red were OM 31(5) and the most green were COF 33(5). Conclusions: Among these lesions maturity of intermediate and thick bundles varied significantly. We conclude that the study of thick fibres is best suited to differentiate them.