A 58-year-old woman with a history of metastatic uterine leiomyosarcoma presented with a 1-month history of a nonpruritic rash on her arms.
On examination, hyperpigmented plaques were observed on the dorsa of both hands at the sites of previous intravenous access. The darkened skin extended up the arms in a linear pattern along the network of superficial veins; the lesions were palpable but non-tender.
What is the most likely diagnosis?