At low power (original magnification ×10; Figure 2), the lesion consists of circumscribed, nonencapsulated collections of small and medium-sized dermal vessels and variable inflammatory cells. The overlying epidermis is relatively normal. On examination at a higher power (original magnification ×40; Figure 3), these vessels are lined by plump endothelial cells with large nuclei and abundant eosinophilic cytoplasm that protrude into the lumen, resulting in a “tombstone” or “hobnail” appearance. The inflammatory cells consist mainly of lymphocytes and eosinophils.
CARRIE ANN RC, SENAIT ANN WD, MOLLY AH, VINCENT L. Multiple Papules and Nodules of the Scalp—Diagnosis. Arch Dermatol. 2010;146(8):911-916. doi:10.1001/archdermatol.2010.173-b