[Calcifying tendinosis of the pectoralis major muscle with intraosseous migration]

Calcifying tendinosis is characterized by macroscopic deposits of hydroxyapatite within the tendon. Most cases involve the tendons of the rotator cuff, fundamentally the supraspinous tendon, and less frequently other tendons in practically any location. Cortical erosion with intraosseous migration of calcium deposits is rare. An atypical location combined with bone involvement can often lead to confusion with other processes like an infection or malignant tumor resulting in unnecessary biopsies or interventions. We present the case of a man who presented with pain and loss of function of the shoulder. Plain-film X-rays showed an erosion of the anteromedial cortex of the proximal diaphysis of the humerus with extra- and intra-osseous calcifications that made us suspect an infectious or malignant process. The findings at computed tomography, together with the clinical and radiological course, were key in enabling us to recognize this atypical presentation of calcifying tendinosis of the pectoralis major muscle.