Helical CT of skeletal muscle metastases from primary carcinomas

To determine the clinical and helical CT findings in patients with skeletal muscle metastases from carcinoma, we reviewed the cases of 15 consecutive patients who had muscle metastases diagnosed by contrast-enhanced helical CT.

Between February 1992 and August 1997, 15 patients (30 lesions) had metastatic disease to muscle from primary carcinoma diagnosed by helical CT in our institution. Patient data and imaging findings were retrospectively reviewed.

Ten of 15 patients (67%) were known to have a malignancy at the time of CT. Patients complained of pain at the site of skeletal muscle metastases in five (17%) of 30 lesions, and in 11 (37%) of 30 lesions a mass was palpable. Lesion size averaged 3.2 cm (range, 0.7-7.8 cm). Thirteen of 15 patients had metastatic disease elsewhere at the time of skeletal muscle metastasis diagnosis. Muscles and other structures most commonly involved by metastatic disease included erector spinae (n = 9), psoas (n = 4), rotator cuff (n = 4), gluteal (n = 3), and abdominal (n = 3). The most common appearance of metastatic disease to muscle on contrast-enhanced helical CT was that of a rim-enhancing mass with central hypoattenuation in 25 (83%) of 30 lesions.

Metastatic disease to skeletal muscle tends to be found in people with advanced-stage neoplasms. It may be an incidental finding on CT because pain is an uncommon feature; a minority of lesions were palpable in our series. The most common appearance on contrast-enhanced helical CT is a rim-enhancing intramuscular lesion with central hypoattenuation.