A 61-year-old woman with leukemia abruptly develops an intensely itchy rash. Physical examination demonstrates multiple erythematous patches of the distal arms and legs, some of which involve the palms and soles. Some of the patches show central clearing with surrounding erythematous
rings. Which of the following is the most likely diagnosis?
a. Erythema migrans chronicum
b. Erythema multiforme
c. Kaposi's sarcoma