Urticaria Pigmentosa

Comments:
Sheets of uniform-appearing mast cells in reticular dermis from a case of urticaria pigmentosa. The neoplastic mast cells are histologically similar to normal mast cells. They are oval, polygonal, or spindle shaped and have moderately abundant eosinophilic or amphophilic cytoplasm with faintly visible granules. The nuclei are round to oval with clumped chromatin and inconspicuous nucleoli. Binucleated or multinucleated cells may be present. Cytologic atypia is not a common feature.