NONFAMILIAL TUMORAL CALCINOSIS ASSOCIATED WITH CHRONIC-RENAL-FAILURE AND SECONDARY HYPERPARATHYROIDISM - REPORT OF 2 CASES WITH CLINICOPATHOLOGICAL, IMMUNOHISTOCHEMICAL, AND ELECTRON-MICROSCOPIC FINDINGS

The clinical and pathological findings, including those of immunohisto chemical and ultrastructural studies, of two cases of tumoral calcinos is-like lesion (TCL) are described. Both cases were associated with ch ronic renal failure and hyperparathyoidism. One case presented as a ra pidly growing 20-cm multiloculated, cystic, calcific gluteal mass on t he sacrum, which was not clinically suspected to be related to hyperpa rathyroidism. The other case presented as a 2.5-cm calcific mass on th e right foot that recurred after surgical excision as a 7-cm mass, whi ch was clinically presumed to be related to secondary hyperparathyroid ism. Light microscopic and immunohistochemical studies on both cases a nd ultrastructural studies on one case indicated that the calcifying p rocess involved histiocytes and osteoclast-like giant cells of histioc ytic origin lining the cystic cavities. Hydroxyapatite crystal formati on and calcification appeared to develop predominantly from intracytop lasmic membrane hound vesicles and also from mitochondria These findin gs are similar to those recently reported for familial tumoral calcino sis, which support its having a mechanism of calcification comparable with that of a TCL. This is a US government work. There are no restric tions on its use.