Pulmonary lymphomas simulating lymphomatoid granulomatosis.

Twenty cases of malignant lymphoma presenting in the lung and 10 cases with secondary pulmonary involvement were studied. All cases shared the feature of prominent vascular infiltration by lymphoid cells, and in the 20 cases presenting with pulmonary involvement, this feature led to confusion with lymphomatoid granulomatosis. Both the primary and secondary lymphomas showed similar histologic features including vascular infiltration, extensive necrosis, and foci of a histologically polymorphous and benign infiltrate. The diagnosis of lymphoma was based on the identification of monomorphous foci of atypical lymphoid cells except in the cases of Hodgkin's disease. The malignant cells were occasionally focal and microscopic and surrounded by an extensive histologically benign infiltrate. Examination of several blocks was often required in such cases before a diagnosis of lymphoma could be made. The clinical and radiologic findings at presentation were nonspecific. Radiologic findings included unilateral or bilateral nodules and infiltrates. The prognosis of the 20 patients who presented with pulmonary lymphoma was poor; half were dead in less than 2 years.