Background: The association between dermatomyositis and breast carcinoma has not been fully evaluated yet. The aim of the study was to clarify characteristics of the association between these two diseases.
Methods: The medical records of 128 patients with dermatomyositis or polymyositis from 1990 to 1998 were retrospectively reviewed. Eight patients (6.3%) were identified with dermatomyositis which was associated with an underlying breast carcinoma. Clinical features, laboratory data, electromyograms, muscle biopsies, and the prognoses of these patients were assessed.
Results: The mean age of the 8 patients with breast carcinoma and dermatomyositis (62.1 +/- 6.7 years) was larger than that of patients with breast carcinoma without dermatomyositis (48.5 +/- 11.8 years). Dermatomyositis preceded breast carcinoma in 2 patients, was concurrent with breast carcinoma in 5 patients, and followed breast carcinoma in 1 patient. Of these 8 patients, 4 had TNM classification stage IV (M1) breast cancer, 1 had IIIA (T2N2M0) breast cancer, and 3 had IIB (T2N1M0) breast cancer. The follow-up period ranged from 2 to 79 (median, 21) months. Five patients died of recurrence or distant metastasis, and the remaining 3 patients had disease-free survival, with a follow-up period ranging from 11 to 28 (median, 20) months. Four of 5 patients had parallel improvement in dermatomyositis after surgical treatment of breast carcinoma.
Conclusion: In Taiwan, dermatomyositis is associated with an increased incidence of breast carcinoma. The mean age of the 8 patients with breast carcinoma and dermatomyositis was significantly larger than that of patients with breast carcinoma without dermatomyositis. If present, breast carcinoma can precede, occur concurrently with, or follow the diagnosis of dermatomyositis. Surgical treatment of breast carcinoma may alleviate the course of dermatomyositis and eliminate the need for steroids in some cases.