Malignant soft tissue tumors of the biceps muscle mistaken for proximal biceps tendon rupture.

Tears of the proximal long head of the biceps tendon are among the most common tendon tears in the body. In most cases, the diagnosis is easily determined based on the history and physical examination. However, malignant soft tissue tumors can simulate proximal biceps tendon tears. Although tumors simulating tears of the distal biceps tendon at the elbow have been reported, to the authors' knowledge, no previous cases of tumors simulating or being mistaken for proximal biceps tendon tears have been reported.This article describes 2 cases of malignant sarcomas initially mistaken for tears of the long head of the biceps tendon. In the first case, a 62-year-old woman developed swelling in her arm after feeling a twinge in her shoulder. A magnetic resonance imaging scan was misread as a biceps tendon tear and not treated by the examining physician. In the second case, a mass appeared with little trauma in the brachium of a 70-year-old man. On physical examination, the mass was hard to palpation. In each case, biopsy revealed a soft tissue sarcoma. Both patients underwent wide excision with radiation and are currently disease free. These 2 cases emphasize the importance of obtaining a good history and of performing a thorough shoulder and arm examination in patients with deformities consistent with tears of the long head of the biceps tendon.