Nine cases of chromophobe cell renal carcinoma are reported, 2 in pregnant women. One neoplasm progressed and the patient died of disease, and this tumor presented the highest mitotic index and focal positivity to Ki-67 antibody. DNA flow-cytometric study discovered 89% of aneuploidy, with 3 tetraploid cases. We conclude that chromophobe cell renal carcinoma is a relatively indolent but clearly malignant neoplasm. We suggest that the mitotic index could be the best method to predict malignant behavior. The high incidence of aneuploid cell lines may be due to structural anomalies; it is not indicative of malignant behavior.

A cas e of primary ma lignant myxoid fibrous histio cytoma of th e lung presenting as a solitary lung nod ule in a 61-year-o ld man is presented. This tumor aro se in a patient with a t ranslt iona l-cell carci noma of the urinary bladder and a well differ e ntiated squa mous-cell ca rcinoma of t he lar ynx. The differe nt ial d iagnosis between a primary lung tu mor versus a solita ry metastas is is difficult a nd was supported by histological features and t he lack of epit helial prop erties proved by lmrnunohlstochernistr y. Tobacco was th e only etio logic facto r know n in t he patien t.