Tumoral calcinosis (TC) is a rare condition characterized by the deposition of calcium phosphate salts in juxta-articular soft tissues, resulting in hard, tumor-like masses. The most common sites of involvement are the extensor aspects of the joints of the upper limbs. The masses may be solitary or multiple and enlarge slowly over time. They are usually painless, although discomfort or pain may develop in cases of inflammation, pressure, or nerve compression. Rarely, TC can affect periarticular ligaments and extend into the joint space. Further complications include limitation of joint function, carpal tunnel syndrome, ulceration, and secondary infection.

TC may be primary (familial) or secondary. It may also be idiopathic.

Primary TC may be hyperphosphatemic (HPTC) or normophosphatemic. It is most commonly reported in people in and descended from Central Africa and the Middle East. Onset is typically in childhood or adolescence in the primary forms. GALNT3, FGF23, and KL mutations have been found in the hyperphosphatemic form and SAMD9 mutations in the normophosphatemic form.

Secondary TC is associated with underlying chronic kidney disease (CKD), wherein secondary or tertiary hyperparathyroidism causes dysregulation of calcium-phosphate metabolism, leading to soft tissue calcifications. TC may also be seen in the setting of an underlying connective tissue disease, including systemic lupus erythematosus (SLE), dermatomyositis, systemic sclerosis, and rheumatoid arthritis.