CASE REPORT
A 68-year-old woman with multiple myeloma (MM), refractory
to bortezomib and combination chemotherapy,
presented with a 1-week history of enlarging and tender lesions on the left arm. The patient was diagnosed with multiple myeloma seven months prior to presentation with involvement of multiple skeletal sites, including the left shoulder, spine, and pelvis. Initial pelvic bone biopsy revealed
sheets of lambda light chain-restricted plasma cells.
Physical examination revealed sharply demarcated, 5 mm to 10 mm, red-to-violaceous, smooth-topped firm papules, coalescing
into 1 cm to 3 cm plaques with slight peripheral scale, clustered on the left arm (Figure 1a). A solitary 5 mm red papule
was identified on the right leg (Figure 1b). Skin biopsies obtained from the left arm and right leg both revealed atypical epithelioid cells with prominent nucleoli and numerous mitotic figures, which stained strongly with antibodies against CD138 and lambda light chain, but did not stain with antibodies against kappa light chain (Figure 2a-2e), establishing the diagnosis of cutaneous plasmacytomas.
DISCUSSION
Plasma cell tumors involving soft tissue or the axial skeleton are referred to as plasmacytomas.1 The International Myeloma Working Group classified plasmacytomas into solitary plasmacytomas
of bone, extramedullary plasmacytomas, and multiple plasmacytomas, which can be either primary or secondary depending
on the absence or presence of systemic plasma cell disease, respectively.2-4 Secondary cutaneous plasmacytomas,
OHincluding those observed in the setting of MM, most commonly arise from contiguous extension from an underlying focus of bony disease, or more rarely, from hematologic metastases to the skin.5 In our patient with MM, the presence of cutaneous plasmacytomas involving 2 distinct sites, and malignant plasma cells within the dermis without infiltration into the subcutaneous
fat, suggest a diagnosis of metastatic MM to the skin.4
CONCLUSION
Multiple myeloma metastases are typically seen in cases with high systemic plasma cell tumor burden, and portend a very poor prognosis with death occuring most often within 1 year of diagnosis.
5-8 Treatment is generally targeted at the underlying systemic
