S1C20P10-2: This distribution of mast cells, as seen in this field of a mastocytoma, is common; the relationships suggest that this is a preferential site of residence for mast cells.

S1C20P10-4: The infiltrates of this area are loose; they are both perivascular and interstitial. The epidermis shows hyperplasia of the basal unit with elongation of rete ridges. There is some widening of spaces among collagen bundles, a feature that might be cited as evidence of dermal edema. On the other hand, collagen bundles are slightly coarsened; the lesion has a sclerotic quality.

S1C20P10-5: Interstitial infiltrates are prominent. The infiltrate could easily be dismissed as lymphoid at this magnification (too high to qualify as “pattern analysis?). On closer inspection, some of the nuclei are elongated and show uniform chromatin patterns. The widened spaces among collagen bundles are evidence of dermal edema.

S1C20P10-6: The nuclear characteristics of many of the cells are not those of a lymphocytic infiltrate. In addition, many of the cells have lavender cytoplasm; this tinctorial quality is more evident on this digital photograph than on visual examination of the histologic section.

S1C20P10-7: With a giesmsa stain, many of the cells of the dermal infiltrates contain lavender, metachromatic granules in the cytoplasm; these cells are mast cells.