First Department of Pathology, Kansai Medical University, Osaka, Japan.
A case of malignant ameloblastoma with hypercalcemia in a 67-year-old Japanese woman is presented. The tumor of the maxilla was removed and diagnosed as a follicular ameloblastoma. The tumor recurred in the lower orbita-zygoma region, and multiple tumors of the lungs and hypercalcemia were detected eight months after the second operation. The recurrent tumor resembled the primary tumor but was less well differentiated. Autopsy revealed widespread lung metastasis of the malignant ameloblastoma, nephrocalcinosis, and sigmoid colon cancer. Histologic examination showed the metastatic ameloblastoma to be composed of nests and strands of basaloid and spindle-shaped cells surrounded by columnar cells arranged in palisade formation, with focal areas of squamous differentiation and occasional cystic degeneration. Only two cases of malignant ameloblastoma with hypercalcemia have previously been reported. This is the first case of malignant ameloblastoma with hypercalcemia and sigmoid colon cancer. In addition, prostaglandin E2 assay revealed that ameloblastoma produces prostaglandin E2, which results in hypercalcemia.