Annular erythema as a sign of recurrent breast cancer.

Three women with known breast cancer presented with very similar annular erythemas of their chest walls. All women were in remission from their breast cancer for at least 6 months. Their breast cancers had initially responded well to multi-modality treatment with no clinical or radiologic evidence of recurrence, until the development of the annular erythema. In the first case, the annular erythema was treated unsuccessfully as a dermatitis and then as tinea corporis. In the second case, subacute cutaneous lupus was considered but lupus antibodies were negative. In the third case, the annular erythema was promptly recognized and biopsied. Histology in all three cases revealed identical findings of invasive ductal carcinoma involving the lymphatics of the skin. Immunohistochemical staining of the carcinoma was positive for human epidermal growth factor receptor 2 but negative for oestrogen and progesterone receptors. Annular erythema can pose a wide differential but rarely has it been described as a sign of locally recurrent cancer. These cases highlight the importance of recognizing this entity in the oncologic patient, where prompt skin biopsies can confirm the diagnosis and allow early initiation of therapy.