Abstract
Multiple myeloma is a malignant plasma cell proliferation producing a monoclonal immunoglobulin. The typical organ manifestations are summarized under the acronym CRAB, HyperCalcemia, Renal insufficiency, Anemia, lytic Bone lesions. Multiple myeloma accounts for approximately 20% of hematologic malignancies. Cutaneous involvement of multiple myeloma is very rare with fewer than 100 cases described in the literature so far. We report a 70-year-old man with history of multiple myeloma type IgG kappa and skeletal involvement. He was treated with radiotherapy, chemotherapy and autologous stem cell transplantation. Nearly complete remission was achieved under therapy. The patient presented in our outpatient clinic with 3 indolent, indurated, livid-erythematous nodules - on the left thigh, scrotum and in the gluteal region. A punch biopsy showed beneath a grenz zone in the dermis densly packed enlarged pleomorphic cells with prominent nucleoli and bright cytoplasma. Immunohistochemistry showed diffuse expression of CD 138, CD79 and light chain kappa, but negative for S100, CD3, CD20 and CD30. Molecular pathology showed evidence of B-cell clonality confirming the diagnosis of cutaneous manifestation of multiple myeloma. The patient was referred to the department of clinical hematology, where a therapy with revlimid/dexamethasone was reinduced. Histology usually shows nonencapsulated, diffuse, dense infiltrates mostly within the reticular dermis but sometimes involving the subcutis. The cells retain some features of conventional plasmacells (e.g. perinuclear hof, eccentric nucleus). In most cases there is immunohistological expression of CD38, CD138 and CD79a, whereby most B-cell associated markers and leukocyte common antigen (CD45) are negative.