Skin metastasis of breast cancer clinically undistinguished from amyopathic dermatomyositis.

We report a 65-year-old woman who consulted us on May 25, 1998, showing pruritic, partially flagellate erythema on the back and upper extremities, livedo lesions with erythema on the loins, and erythematous papules on the dorsal finger joints for 2 months. Histopathological findings of erythema on the back showed mononuclear cell infiltration around capillaries and marked edema in the dermis. Laboratory data were within normal range except for positive anti-nuclear antibody. She had undergone total left mastectomy on June 2, 1997 for breast cancer. Supraclavicular lymph node metastasis was found at the beginning of May, 1998. A diagnosis of amyopathic dermatomyositis associated with breast cancer was made. Erythema with itching gradually subsided from the end of August, 1998. Treatment with radiation and chemotherapy reduced lymph node swelling, but complete remission was not obtained. Erythema similar to the previous lesion but without itching re-appeared on the back from January, 2000. Histological findings of erythema showed many carcinoma cells similar to the primary lesion of left breast cancer in the whole dermis. A diagnosis of skin metastasis of breast cancer was made. These findings suggest that skin metastasis should be taken into account for patients with erythema on the trunk similar to dermatomyositis.