Skin Lesions in Patient With Metastatic Breast Cancer

December 3, 2017

A 57-year-old woman with metastatic HER2/neu-positive breast cancer started treatment with a combination of docetaxel, pertuzumab, and trastuzumab. On the fourth cycle the patient complained of mild irritation and a skin rash on her left upper extremity. What is your diagnosis?

A 57-year-old woman with metastatic HER2/neu-positive breast cancer started treatment with a combination of docetaxel, pertuzumab, and trastuzumab. On the fourth cycle the patient complained of mild irritation and a skin rash on her left upper extremity. She denied significant pain and pruritus. She did not report fever, fatigue, headache, or flu-like symptoms. On exam, the right upper arm revealed an erythematous patch along the C6 dermatome. A cluster of punctate hemorrhagic vesicles with crust and scale was noted centrally (left). A Giemsa stain of the scrape and smear obtained from the lesion is shown below (right).

Based on the images shown, what is your diagnosis?