Abstract
Cutaneous Metastases of Breast Cancer During Anti-HER2 Therapy: Diagnostic Challenges
Department of Dermatology, Jagiellonian University Medical College, Krakow, Poland
Doctoral School of Medical and Health Sciences, Jagiellonian University Medical College, Krakow, Poland
Department of Dermatology and Allergology, University Hospital, Krakow, Poland
Student Scientific Group of Dermatology, Jagiellonian University Medical College, Krakow, Poland
Dermatol Rev/Przegl Dermatol 2026, 113, 164–169
Introduction
Cutaneous metastases occur in up to 25% of patients with metastatic breast cancer and may mimic drug reactions or inflammatory dermatoses.
Objective
This case highlights the diagnostic challenges associated with evaluating skin lesions in a patient undergoing HER2-targeted therapy for metastatic breast cancer.
Case report
We present a 52-year-old woman with HER2-positive breast cancer (pT4pN1cM1) who developed recurrent erythematous skin lesions during treatment with trastuzumab and pertuzumab. Initial biopsies showed no evidence of malignancy, and empirical anti-inflammatory treatment was ineffective. Repeated skin biopsies performed after corticosteroid therapy revealed intravascular tumor emboli within cutaneous vessels. Imaging studies revealed progression of visceral metastases. The patient was subsequently treated with trastuzumab emtansine and later trastuzumab deruxtecan.
Conclusions
This case underscores the importance of careful clinical assessment and clinicopathologic correlation in patients receiving anti-HER2 therapy who develop atypical skin lesions, as such lesions may be associated with systemic progression of cancer.
Keywords
breast cancer, cutaneous metastases, trastuzumab, pertuzumab
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