Morphometric characteristics of Malassezia sp. stained with picrosirius.

The genus Malassezia has been considered an emergent pathogen [4] and could be found in seborrheic dermatitis lesions as spherical yeast cell shapes and in pityriasis versicolor forming short hyphae with yeast cells [3]. Picrosirius is used in histology to stain collagen [5] and has been also used to stain Cryptoccoccus spp. and Paracoccidioides brasiliensis [1,2]. However, there are not studies using this technique to stain Malassezia sp. and determining the dimensions of the fungus in human tissue material. This study describes the staining of the yeast from the genus Malassezia sp. by picrosirius and the morphometry of this fungus in tissue samples from ten cases of autopsies made in the year 2000. The autopsied people were 26 to 91 years old, seven of which were men. The samples were collected, paraffin embedded, and stained using the hematoxylin and eosin, Grocott and picrosirius techniques. The interactive morphometry analysis of Malassezia sp. was made from picrosirius stained slides under polarized light by the automatic image analyzer system KS 300 Carl-Zeiss (Germany). The area, maximum and minimum diameters were quantified in 96 fungi samples defined by the accumulated mean test. The dimensions were expressed in mean or median according to the Kolmogorov-Smirnov normality test. Malassezia sp. was found as spherical or oval structures with staining varying from orange to pink after picrosirius staining and analysis under light microscopy (Figure A). The yeasts with a single bud and filamentous forms were frequent (Figure A). Most of the fungi showed spherical structures or “Maltese cross” shape and the color varied from golden to copper under polarized light analysis (Figure B). The glow was less intense or absent in 82 Rev Iberoam Micol 2007; 24