B cell lymphoma presenting as carcinoma of the lung.

A patient presented with superior vena caval obstruction caused by a tumour which resembled carcinoma of the lung both clinically and histologically. However, immunologic and cytogenetic analyses carried out on the mediastinal biopsy and on pleural fluid revealed that the tumour was of B cell origin, Burkitt-like in sub-type, and had the t(8;14) translocation. The nature of many poorly differentiated tumours may be more clearly identified with the help of immunological and cytogenetic analyses.