Extraosseous extension of multiple myeloma: A cutaneous herald to systemic disease
Authors: Chante Karimkhani, Christopher Smith
Journal: Journal of the American Academy of Dermatology (2014)

To the Editor: Cutaneous involvement of multiple myeloma is an extremely rare manifestation, typically presenting as an extraosseous extension to the skin.1Damaj G. Mohty M. Vey N. Dincan E. Bouabdallah R. Faucher C. et al.Features of extramedullary and extraosseous multiple myeloma: a report of 19 patients from a single center.Eur J Haematol. 2004; 73: 402-406Crossref PubMed Scopus (105) Google Scholar Presentation of these cutaneous lesions occurs more often in late stage multiple myeloma with a high tumor burden.2Requena L. Kutzner H. Palmedo G. Calonje E. Requena C. Perez G. et al.Cutaneous involvement in multiple myeloma: a clinicopathologic, immunohistochemical, and cytogenetic study of 8 cases.Arch Dermatol. 2003; 139: 475-486Crossref PubMed Scopus (96) Google Scholar A single-center retrospective study reported a 2.3% incidence of extramedullary and extraosseous tumor at the time of multiple myeloma diagnosis. Furthermore, cutaneous appearance and histopathology do not predict systemic disease and should alert the dermatologist to a need for further evaluation.3Torne R. Su W.P.D. Winkelmann R.K. Smile J. Karl H. Clinicopathologic study of cutaneous plasmacytoma.Int J Dermatol. 1990; 29: 562-566Crossref PubMed Scopus (53) Google Scholar We report a case of multiple myeloma presenting as an extraosseous extension mimicking a cutaneous mass. A previously healthy 62-year-old woman presented with an asymptomatic left forehead mass of 1 month's duration. On examination, the 3.5- to 4-cm mass was nontender and nonfixed, and appeared subcutaneous. Two days later, the patient presented for excision of the left forehead mass. Blunt dissection uncovered a deeper subfrontalis grayish mass that was slightly firm and 3.5 to 4 cm in diameter. Careful dissection at the periosteal plane of the left frontal bone demonstrated a ragged 1.5-cm outer table bony defect. Biopsy specimen of the mass was obtained and the wound was closed. Because of the potential for intracranial involvement, the patient was sent for immediate magnetic resonance imaging (MRI) of the left frontal soft tissue bone and brain (Fig 1). The MRI scan revealed a large expansile enhancing mass anteriorly in the left frontal bone and several smaller enhancing masses in the calvarium. Pathology of the biopsy specimen revealed a monomorphous proliferation of medium to large neoplastic-appearing plasma cells, strongly positive for CD138, CD38, and lambda light chain, but negative for kappa light chain (Fig 2). Lambda-positive cutaneous plasmacytoma was diagnosed and the patient was referred to an oncologist for further workup. Bone marrow biopsy demonstrated a 50% cellular bone marrow comprised of approximately 25% plasma cells, all with a 46XX karyotype. Subsequent computed tomography and positron emission tomography scan showed osseous lesions in the axial and appendicular skeletons, lytic lesions in the skull and distal right humerus, multiple rib fractures, and scattered lucent lesions in the bilateral third ribs, left fifth rib, right seventh rib, and left clavicle. Lambda light chain−restricted multiple myeloma was ultimately diagnosed. She underwent initial radiotherapy to the forehead, followed by aggressive induction chemotherapy with lenalidomide and dexamethasone. Eight months after her initial dermatologic presentation, the patient underwent stem cell collection followed by high-dose melphalan autologous stem cell transplantation. She recovered all cell counts following the transplant and was maintained on prophylactic antimicrobials per protocol. A 15-month course of lenalidomide maintenance therapy was initiated in addition to zoledronic acid at tri-monthly intervals for the prevention of skeletal fractures. At her 3-month bone marrow biopsy and 1-year follow-up following stem cell transplantation, the patient continued to be in a stringent complete first response. She continues to tolerate maintenance treatment well and follows up with her oncologist intermittently.Fig 2Diffuse infiltration of plasma cells with characteristic round oval cells, eccentric nuclei, and moderate cytoplasm. (Hematoxylin-eosin stain.)View Large Image Figure ViewerDownload Hi-res image Download (PPT)