Objective: The purpose of this study is to compare the capsular structure appearing in follicular adenoma and papillary thyroid carcinoma to differentiate the benign and malignant thyroid nodules. Methods: Second Harmonic Generation (SHG) Microscopy was used to image collagen distribution in the capsules of several types of nodules. The tissue fragments were formalin-fixed, paraffin-embedded but without H&E staining, with 4-5 microns thick sections. From the same sample, two consecutive sections were made. The first was colored with H&E and capsule images were acquired with an optical microscope. The second was not colored with H&E. On the uncolored sample, type I collagen from the capsule was visualized by SHG microscopy. In addition, a parameter was used to study the orientation of collagen fibers, obtained from the Fast Fourier Transform (FFT) analysis of 2D-images. Results: SHG microscopy images were acquired to assess the collagen organization of tumoral capsular thyroid nodules previously diagnosed as benign or malignant by conventional H&E staining. Different degree of collagen fibers orientation was observed from the two kinds of capsules and quantified using FFT analysis. Conclusion: These above described microscopy method can be used to distinguish between benign and malignant thyroid nodules, based on different degree of the capsular collagen fibers orientation.
