Primary cardiac lymphoma presenting as an atypical type of hypertrophic cardiomyopathy.

Primary cardiac lymphoma (PCL) is a very rare malignancy although cardiac involvement with the disseminated disease is not uncommon. We present a case of a 43-year-old man with PCL that initially presented as marked thickening of all cardiac walls and was mistakenly diagnosed as an atypical type of hypertrophic cardiomyopathy. The diagnosis of PCL was made with a delay of 9 months after the initial presentation, when atypical lymphocytes staining positive for CD79a and CD20 were demonstrated in the rapidly growing mediastinal and neck mass. Anthracycline-based chemotherapy and anti-CD20 immunotherapy resulted in a remarkable reduction in cardiac wall thickness and mediastinal mass. The first lesson to be learnt from this case is that PCL can present as a diffuse infiltrative disease without a mass. The second lesson is that prompt exploratory thoracotomy should not be delayed when the diagnosis is elusive.