[Skin location of multiple myeloma mimicking a vascular tumor]

Cutaneous location of multiple myeloma is rare, and generally develops as a consequence of direct spread from an underlying bony focus of the disease. Metastatic skin lesions without adjacent bone involvement are uncommon. The prognosis is very poor.

A 74-year-old man consulted for a hemorrhagic cutaneous nodule localized on the left inguinal area. This patient had been treated for five months for a stage I IgG lambda multiple myeloma. The histopathologic examination of the lesion showed a predominantly nodular configuration made up of masses of atypical cells with numerous hemorrhagic areas. The diagnosis of cutaneous metastasis of multiple myeloma was confirmed by the positivity of the cells for anti-IgG lambda antibodies.

Cutaneous involvement in multiple myeloma without extension from underlying bony focus is exceptional. The lesions generally consist of firm, erythematous nodules involving the neck and lower extremities. To our knowledge, we present here the first case mimicking clinically and histologically a malignant vascular proliferation.