Calcifying Collagenolysis (Tumoural Calcinosis)

In calcifying collagenolysis (tumoural calcinosis) the primary lesion is a digestion of collagen near joints or bones by cells with the morphology and functions of osteoclasts. This is accompanied or followed by calcification in the digestion fluid in the form of minute granules, as the necessary alkalinity and alkaline phosphatases are present. Sequestrated masses of digested collagen in this fluid can usually be recognised by their high content of argyrophilic reticulin and exceptionally by Van Gieson's or other stain for collagen. Calcification is therefore secondary and is not associated with any disturbance of calcium or phosphorus metabolism, though minor increases in serum phosphorus may be found when the lesions are large and active. The process differs from other examples of dystrophic calcification in that it is associated with an increased and not a reduced vascularity, and is progressive and selfperpetuating. The disease is basically the opposite of myositis ossificans, and like it is the result of metaplasia of connective tissue cells and not of disturbed calcium and phosphorus metabolism. The histological picture is typical and diagnostic and is readily differentiated from other chronic inflammatory or degenerative lesions in collagen.