Rotator cuff metastases: a report of two cases with literature review.

Context: Distant metastases of primary malignancies to the skeletal muscle tissue are a very rare event. Distant metastases that affect the rotator cuff are even rarer, and only a few of cases have been reported so far.

Case Report: The present article reports two cases that presented to our hospital with the complaint of shoulder pain and had a soft tissue mass affecting the muscles of the rotator cuff and invading the neighboring bone compartments. One of the patients developed mucoepidermoid cancer metastasis of the submandibular gland, and the other was found to have a malignant epithelial tumor metastasized from the lower lobe of the right lung, whose primary origin could not be diagnosed until the imaging examinations were employed. Ultrasound and magnetic resonance imaging findings are presented in this paper.

Conclusion: Metastases to the muscle tissues could be misdiagnosed as primary sarcomas. Because the therapy regiments and prognoses are fairly different for these two entities, the possibility of a metastasis to the muscle tissue must be considered as a differential diagnosis for case of painful soft tissue mass. Ultrasound is very useful in detection of the lesion and acts as a very important tool during guidance for biopsy. Magnetic resonance imaging, however, is a very valuable asset in the evaluation of the borders of the soft tissue mass and its invasive effect on the bony tissues. Particularly when the features such as lobulated contours, peripheral edema, and intratumoral necrosis exist, the possibility of metastases must be considered.