Specific cutaneous involvement in patients with multiple myeloma is very rare. When it does occur, it is in patients with advanced stages of multiple myeloma and with a large tumorous mass. In this study, we analyzed 40 patients with specific cutaneous involvement from multiple myeloma, with no bony lesions underlying the skin lesions, and we reviewed the related literature.
We were particularly interested in the clinical course of these patients, including survival once skin metastases had developed and the possible influence of the different treatments administered.
The study was completed by determining the histopathological pattern, the immunohistochemical profile, the type of immunoglobulin and immunoglobulin light chain produced by the neoplastic plasma cells that infiltrated the skin, as well as the cytogenetic characteristics of these cells.
From a clinical standpoint, the skin lesions consisted of multiple nodules or plaques with erythematous or violaceous coloration, and variable location. Histopathologically, two patterns were seen: nodular and diffuse interstitial. The plasma cells showed cytological atypia, and in one case they displayed a spindle shape, giving the lesion a sarcomatoid appearance. Immunohistochemically, these neoplastic plasma cells were strongly positive for CD79a, CD138, and EMA, while the immunoexpression of CD38 and CD43 was less intense and constant. In 39 of the 40 patients, the type of monoclonal immunoglobulin produced by the neoplastic plasma cells in the skin lesions was determined: 18 patients had IgA myeloma (5 IgAkappa and 13 IgAlambda), 19 patients had IgG myeloma (15 IgGkappa and 4 IgGlambda) and 2 patients had IgDlambda myeloma. The 22 cases in which immunoglobulin heavy chain gene rearrangement studies by PCR were carried out for the JH gene showed monoclonal rearrangement, while viral studies to try to identify genetic material of the HHV-8 virus and the Epstein-Barr virus gave negative results in all cases. These 22 cases studied using FISH showed the deletion of the rb-1 retinoblastoma gene in the neoplastic plasma cells that infiltrated the dermis. Despite aggressive chemotherapy, all of the patients died a few months after the skin lesions developed.
In our series, a perfect correlation was seen between the findings of serum electrophoresis and the immunohistochemistry of the skin lesions with regard to the type of immunoglobulin and the immunoglobulin light chain restriction produced by the neoplastic plasma cells. Patients with multiple myeloma have a very short survival period once specific skin lesions appear, regardless of the therapy administered. The deletion of the rb 1 gene may be a prognosis marker to identify those patients with especially aggressive forms of multiple myeloma.