Diagnosis of malignant cardiac disease by endomyocardial biopsy Among oncology patients, endomyocardial biopsy has been used primarily for the evaluation of anthracycline cardiotoxicity. In addition, however, endomyocardial biopsy may be useful for the detection of malignant cardiac neoplasms. Between 1982 and 1989, metastatic involvement of the heart was diagnosed by endomyocardial biopsy in seven patients at our institution. All except one of these patients were older than 50 years of age and had dyspnea as an initial symptom, and all had a known malignant lesion. Results of endomyocardial biopsy confirmed cardiac involvement by a hematologic malignant lesion in four patients and metastatic melanoma in two patients. In one patient, who had a history of breast cancer and lymphoma, a metastatic neoplasm of uncertain differentiation was observed. Myocyte damage was evident in endomyocardial biopsy specimens from two of the four patients with hematologic malignant disease. Endomyocardial biopsy was performed to confirm the possibility of metastatic involvement in five patients; in the other two, endomyocardial biopsy was performed to determine whether anthracycline cardiotoxicity was present, and metastatic involvement was unanticipated. 