Russula densifolia produces a white to pale yellow spore print. Spores are oval to elliptical to roughly spherical, hyaline (translucent), amyloid, and measure 7.6–9.5 by 6.7–7.5 µm. They have a rough, reticulate surface marked by ridges and low, isolated warts that are 0.2–0.5 μm high. The cystidia in the hymenium are thin-walled and hyaline, with shapes ranging from club-shaped with broad tips to somewhat fuse-shaped with short and narrow appendages at the tip; cystidia have dimensions of 30–80 by 5–10 µm. Under the hymenium, the subhymenium is starkly differentiated. There are abundant sphaerocysts (fragile, spherical cells common in the Russulaceae) present in the gill tissue, and the cap tissue has clusters of these cells. The cap cuticle, typically 125–200 µm thick, is embedded in a gelatinous layer, and is differentiated into two layers: the epicutis, which consists of interwoven hyphae, and the underlying subcutis. Shaffer attempted to differentiated several forms of the mushroom by differences in cap cuticle thickness and morphology, although these forms are now not considered to have taxonomic significance.
