Atypical cutaneous relapse of multiple myeloma

A 66-year-old patient, diagnosed κ light chains MM with t(11;14), presented before second cycle with bendamustine-dexamethasone. A complete remission was initially obtained with bortezomib-cyclophosphamide-dexamethasone and autologous HSCT. After relapse, he was successively treated with bortezomib-dexamethasone, carfilzomib-dexamethasone, daratumumab-dexamethasone and benda-mustine-dexamethasone. SFLC measurement indicated a partial response but clinical examination revealed a soft pink skin lesion of four centimeters on the left side of the abdomen (A). Puncture of this lesion showed an infiltration of dystrophic plasma cells, with high nucleus-cytoplasm ratio and immature chromatin (B, May-Grünwald-Giemsa, objective × 100) (Figure 1). Flow cytometry and genetic analysis con-firmed monotypic κ plasma cells with t(11;14). External beam radiation therapy was a partial failure and bone plasmocytomas appeared two month later.

Cutaneous plasmocytoma in the setting of an established MM is very rare but associated with a poor prognosis. Venetoclax monotherapy was initiated but the general health of the patient declined dramatically before the initiation of the treatment.