Esophageal undifferentiated carcinoma displaying marked chondroid differentiation at metastatic foci

A report of an unusual esophageal tumor in an 81-year-old man is presented. The primary tumor was diagnosed as undifferentiated carcinoma at biopsy and had disappeared after irradiation treatment. However, multiple metastases were noted in the brain, lungs, kidneys, adrenals and spleen at autopsy. Histologically, metastases showed marked cartilaginous metaplasia as demonstrated by light microscopy, histochemical and immunohistochemical studies, although the initial biopsy sample did not possess chondroid matrix. Furthermore, an apparent transition could be traced from carcinomatous to chondroid cells, suggesting that the chondroid cells were derived from carcinoma cells. The carcinomatous area partially showed both squamous and glandular differentiation, although they were poorly differentiated. A retrospective immunohistochemical study that used a panel of antibodies suggested a phenotypic relevance between primary and metastatic tumors.