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).
D. Herpes zoster infection of the skin
Docetaxel-induced skin toxicity has a variety of manifestations, including erythematous reactions, palmar-plantar erythrodysesthesia, plaque-like erythrodysesthesia, erythema multiforme, nail changes, dermatitis, desquamation, and flagellate erythema. The location and nature of this patient’s lesions are not typical for a docetaxel skin reaction.
Trastuzumab and pertuzumab both target HER2/neu, an epidermal growth factor receptor (EGFR) that is overexpressed in breast cancer cells but also present in keratinocytes of the skin. When used as single agents, these two drugs do not induce the classic acneiform rash seen with other EGFR inhibitors such as cetuximab and erlotinib. However, when used in combination, they have been reported to induce a skin reaction histologically similar to that seen with other EGFR inhibitors. The location and smear preparation of the lesions does not support this diagnosis.
Metastases to the skin from breast cancer are possible; however, the nature of the lesions and smear does not support this diagnosis.
Herpes simplex, varicella, and herpes zoster infections can be rapidly and reliably diagnosed by a Tzanck test. The smear shows characteristic multinucleated syncytial giant cells, acantholytic cells, and inclusion bodies. It is not possible to distinguish between these three conditions based on cytodiagnostic features. The patient’s symptoms and clinical findings help to distinguish between these infections. In this case, the distribution of the eruption in the C6 dermatome confirms the diagnosis of herpes zoster infection.
The patient was treated with acyclovir for 2 weeks, with gradual but successful clearance of her skin lesions.
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2. Mortimer J, Jung J, Yuan Y, et al. Skin/nail infections with the addition of pertuzumab to trastuzumab-based chemotherapy. Breast Cancer Res Treat. 2014;148:563-70.
3. Ruocco V, Ruocco E. Tzanck smear, an old test for the new millennium: when and how. Int J Dermatol. 1999;38:830-4.