Pulmonary pseudolymphoma.

Pseudolymphomas of the lung are extremely rare with approximately 30 cases reported in the literature. Histologically it may be impossible to distinguish a benign pseudolymphoma from a malignant lymphoma. Immunoperoxidase staining has been proposed to help predict the benign or malignant potential of these conditions. Results thus far have been inconclusive, but a monoclonal pattern has tended to predict malignant potential. We have reported a pulmonary pseudolymphoma that failed to stain with the immunoperoxidase technique due to improper tissue fixation. After four years of clinical follow-up, the patient remains disease free.