Histologic examination of the biopsy specimen showed a perivascular and interstitial mast cell infiltrate involving the papillary and middle dermis. The mast cells were round and oval, with abundant granular cytoplasm and a central nucleus. The cytoplasmic granules of the mast cells stained metachromatically with Giemsa stain (Figure 3). These findings were consistent with the diagnosis of cutaneous mastocytosis.
Brownish Reticulate Maculopapular Eruption on the Flexures—Diagnosis. Arch Dermatol. 2003;139(3):381-386. doi:10.1001/archderm.139.3.381-a