Eleven years after undergoing right modified radical mastectomy, a 61-year-old woman develops raised red and purple nodules over the right arm. What is the most likely diagnosis?

Lymphangiosarcoma is a rare complication of long-standing lymphedema, most frequently described in a patient who has previously undergone radical mastectomy (Stewart-Treves syndrome). It usually presents as blue, red, or purple nodules with satellite lesions. Early metastasis, mainly to the lung, may develop if it is not recognized early and widely excised. Lymphedema is a complication of radical mastectomy and presents as diffuse swelling and nonpitting edema of the limb. Lymphangitis and hyperkeratosis are complications of lymphedema.