Histoplasma capsulatum can be identified on GMS stain
of a variety of tissues, including bone marrow, lymph node, skin lesion biopsy, liver biopsy, and transbronchial lung biopsy specimens.
Do the black particles on the GMS stain represent fungi?
Although some laboratories additionally perform a periodic acid-Schiff stain for fungi, the GMS stain is preferable, primarily because periodic acid-Schiff provides less contrast between fungi and background debris.
It is also important to note that, on occasion, a poorly performed GMS stain may yield falsely negative results; thus, it is important to check standard tissue controls in every case.
With a GMS stain, Histoplasma yeasts are small, uniform, and oval (Figures 1, F, and 2, B).
Both organisms are highlighted by the GMS stain, whereby the main differentiating features are the uniform size, oval shape, and occasional tapered forms of Histoplasma as opposed to the nonuniform size, round shape, and lack of tapering of Cryptococcus (Figure 2, B and D).
7,52) As with other fungi, the GMS stain reveals more organisms than initially appreciated on H&E-stained sections.