Multiple Skeletal Muscle Metastases from Colon Carcinoma Preceded by Paraneoplastic Dermatomyositis

Skeletal muscle metastases are very rare events in colorectal carcinoma. By contrast, dermatomyositis is an idiopathic inflammatory myopathy with characteristic cutaneous manifestations and a well-recognized association with several human malignancies and, among others, colorectal cancer. Here, we report the case of a 71-year-old woman with paraneoplastic dermatomyositis followed by the development of a metastatic colon cancer. Interestingly, this patient developed multiple skeletal metastases which were preceded by the worsening of systemic symptoms of dermatomyositis. This observation suggests that, while muscle tissue is usually resistant to the development of tumor metastases, the inflammatory and immune response which characterizes and boosts paraneoplastic myopathy may represent a favorable soil for tumor cell invasion and metastasization to skeletal muscles.