Tumoral calcinosis: a clinicopathological study of 111 cases with emphasis on the earliest changes.

AIMS: To study the pathogenesis of tumoral calcinosis (TC), we investigated 111 cases registered in Zaire over 30 years. METHODS AND
RESULTS: The patients were 108 black Africans and three Caucasians between 3 and 74 years of age (mean, 37.7; median, 39). The gender was known in 33 males and 46 females; in 79 the gender was unknown. All but three were healthy and one had tuberculosis. The majority presented with a painless swelling in single or multiple periarticular regions. The hip was the most commonly affected (57%). Seven recurrences after surgical removal of the mass were reported. On microscopic examination, lesions were classified as follows: 24% stage I, 16% stage II and 60% stage III depending on the cellular activity at the border of the cysts. In five stage I cases only, and in no advanced stage II/III lesions, were exuberant cellular proliferative changes seen adjacent to the classical cystic form. These consisted of either ill-defined reactive-like perivascular solid cell nests admixed with mononuclear and iron-loaded macrophages, or well-organized variably sized fibrohistiocytic nodules embedded in a dense collagenous stroma. These immature changes indicated newly appearing lesions and were assumed to represent the earliest discernible stages in the evolution of TC. The unique well-defined fibrohistiocytic nodules have not been described previously.
CONCLUSIONS: These findings have thus described the full spectrum of lesions occurring in TC. We believe that the adjacent findings are potentially important either in recognizing early stages of the disease or in understanding its pathogenesis.