Cutaneous plasmacytosis with atypical clinical behavior in two dogs.

Cutaneous plasmacytosis (CP) is a rare condition characterized by multiple cutaneous plasmacytomas without multiple myeloma. While no pruritus or spontaneous regression occurs in typical CP, the clinical behavior is limitedly understood due to its low incidence. This case report describes atypical cases of CP. Case 1 had skin nodules on the face and limbs and pruritus, whose pruritus kept progressing. After the diagnosis of CP, the dog died on Day 170 despite the treatment with prednisolone and melphalan since Day 157. Case 2 had multiple skin nodules on the back and abdomen. After the skin biopsy, the nodules regressed without treatment on Day 28. These cases suggest the variation of CP's clinical behavior, which helps further understand the disease.