Cardiac tumors of mice.

Of the 7 primary tumors of the mouse heart, accessed at the Registry of Experimental Cancers, 3 were mesenchymal cell sarcomas, 3 were hemangioendotheliomas, and 1 was a mesenchymoma. The mesenchymal cell sarcomas metastasized via the bloodstream to lungs, kidneys, and spleen. Five of the tumors arose in mice treated with ionizing radiation. Previously, only 3 primary cardiac tumors of mice have been reported. Tumors of the heart as part of multifocal neoplasms of a single histologic type were observed in 3 mice; 2 of these tumors were type B reticulum cell sarcomas, and 1 was a reticulum cell sarcoma not otherwise specified. Of the metastatic tumors of the heart, 12 were from alveologenic carcinoma, squamous cell carcinoma, or carcinosarcoma of the lung, 4 were from sarcoma of the subcutaneous soft tissue, and 1 each was from a subcutaneous transplant of a malignant schwannoma and from an alveologenic tumor of the lung.