Imaging of calcific tendinopathy around the shoulder: usual and unusual presentations and common pitfalls.

Rotator cuff calcific tendinopathy (RCCT) is a very common condition, characterized by calcium deposition over fibrocartilaginous metaplasia of tenocytes, mainly occurring in the supraspinatus tendon. RCCT has a typical imaging presentation: in most cases, calcific deposits appear as a dense opacity around the humeral head on conventional radiography, as hyperechoic foci with or without acoustic shadow at ultrasound and as a signal void at magnetic resonance imaging. However, radiologists have to keep in mind the possible unusual presentations of RCCT and the key imaging features to correctly differentiate RCCT from other RC conditions, such as calcific enthesopathy or RC tears. Other presentations of RCCT to be considered are intrabursal, intraosseous, and intramuscular migration of calcific deposits that may mimic infectious processes or malignancies. While intrabursal and intraosseous migration are quite common, intramuscular migration is an unusual evolution of RCCT. It is important also to know atypical regions affected by calcific tendinopathy as biceps brachii, pectoralis major, and deltoid tendons. Unusual presentations of RCCT may lead to diagnostic challenge and mistakes. The aim of this review is to illustrate the usual and unusual imaging findings of RCCT that radiologists should know to reach the correct diagnosis and to exclude other entities with the purpose of preventing further unnecessary imaging examinations or interventional procedures.