Invasion of poorly differentiated large-cell neuroendocrine tumor of the lung through right pulmonary veins into the left atrium: A very rare case report.

Intracavitary cardiac metastasis is a rare manifestation of primary lung cancer which can be associated with a very poor prognosis. In this condition, the right chambers of the heart are more commonly involved and the invasion of the left atrium (LA) through the venous routes is highly exceptional. Poorly differentiated large-cell neuroendocrine tumors also include only 3% of all primary lung carcinomas which can have adverse outcomes. Therefore, in this report, a rare case of a 72-year-old male patient with poorly differentiated large-cell neuroendocrine carcinoma of the right lung spreading to the LA through the right pulmonary veins was described.