A novel histochemical method for a simultaneous staining of melanin and collagen fibers.

For the histopathologic diagnosis of melanocytic lesions, it could be necessary to identify the melanin pigment because its visualization is unspecific with hematoxylin-eosin (HE). The Fontana-Masson (FM) technique is used in histopathology in this type of lesion, which allows the identification of the pigment, but it loses all the morphologic parameters. The authors describe a modification to the FM method, for the evaluation of the morphology, the argentaffin reaction of the melanin, and collagens fibers of the extracellular matrix simultaneously, for which they have developed the Fontana-Masson picrosirius (FMPS) method. Biopsies of different melanocytic lesions were used for the performance of the HE, FM, and FMPS methods. The pixel intensity of the reaction for melanin, collagen, and epithelium was determined with ImageJ software. The FMPS method allows the evaluation of morphological characteristics, identifying the melanin pigment and collagen fibers with high intensity simultaneously. This method does not differ significantly from FM in the identification of melanin, maintaining its sensitivity and specificity. In addition, it does not differ in the demonstration of the morphology with HE. However, FMPS is significantly superior in the identification of collagen fibers. The FMPS method combines morphological and histochemical parameters that could be useful in the study of pigmented lesions of melanocytic origin.