Primary Cutaneous Plasmacytoma Treated with Palliative Radiotherapy: A Case Report and Literature Review

Introduction: Primary cutaneous plasmacytomas (PCP) are very rare plasma cell neoplasms present in the skin or subcutaneous tissue without underlying multiple myeloma (MM). Case Report: A 78-year-old man was referred to dermatology by wound care for a three-year history of non-healing, enlarging, bleeding lesions on the right lower extremity. Examination revealed multiple firm, tender, slightly mobile erythematous to violaceous nodules ranging from 1 to 5 cm in size, some with erosion and heme crusting. Histopathologic analysis of skin biopsies showed an expansile nodular plasmacytic infiltrate in the dermis. A diagnosis of PCP was made based on clinical and histopathological features. Our patient underwent palliative radiation and responded to the therapy with decrease in size of all lesions Conclusion: We present a case of PCP presenting as multiple erythematous nodules as opposed to a solitary neoplasm, which likely represents a spectrum of variation of one tumor. To diagnose PCP, patients should not meet criteria for MM. All patients with new solitary plasmacytoma should be evaluated with skeletal survey or computed tomography, MRI, and PET/CT to rule out additional lesions. PCPs are usually indolent but 10% to 30% progress to MM within 10 years. Radiation therapy is considered the standard treatment, and additional clinical trials are underway to test the role of adjuvant chemotherapies.