Unusual histiocytic reaction to Monsel's solution.

Monsel's solution for hemostasis was applied to a wound produced at the site of a punch excision biopsy from the wrist of a 51-year-old white man. The biopsy specimen showed an incompletely excised basal cell carcinoma. Thirty days later, the residual carcinoma was excised. Adjacent to a basal cell carcinoma in the second biopsy specimen was an intradermal nodule composed of large polygonal cells and multinucleated histiocytic giant cells containing granules and clumps of dark brown and black pigment. This pigment was strongly positive for iron when stained by Perl's method. This unusual histiocytic reaction to topically applied ferric subsulfate must be differentiated from malignant melanomas and from histiocytic neoplasms with siderosis.