Histologic diagnosis of lymphoproliferative diseases of the digestive tract

The pathologic diagnosis of lymphoproliferative diseases of the gastrointestinal tract is sometimes very difficult or even impossible. In the majority of cases the gross appearance of the lesion is not helpful. Three histological criteria, when present, justify a definite diagnosis: cellular anaplasia and nodal involvement in malignant lymphomas, and the presence of germinal centers in pseudolymphomas. All other histological criteria, including transmural extension of the lesions, are of only relative diagnostic value. The definite diagnosis of these diseases is based on histological examination of the entire lesion. Only a diagnosis of probability is generally possible on endoscopic biopsies. The demonstration of different chains of immunoglobulins by means of immunohistochemistry may help in revealing malignant lymphomas with secretory activity and a polyclonal pattern in reactive lesions.