Multiple, resolving, cutaneous histiocytoma in a dog

Mycosis fungoides was initially diagnosed in a 7.5-year-old German Shepherd Dog with generalized canine cutaneous histiocytoma. Lesions resolved without treatment over approximately 16 weeks. The final diagnosis of histiocytoma with 2 histopathologic patterns was obtained by use of a special staining technique for the detection of lysozyme found in histiocytes.