Middle Eastern intestinal lymphoma: a morphological and immunohistochemical study.

A total of 31 cases of Middle Eastern gastrointestinal lymphoma (from Mosul, Iraq) has been analysed by conventional histology, and also by immunoperoxidase staining of trypsinised paraffin sections with anti-Ig and anti-J chain antisera. Histologically these neoplasms fell into three categories: undifferentiated lymphoma of Burkitt type (8 cases); follicle centre cell (FCC) lymphoma, resembling European lymphomas of FCC origin (15 cases); and Mediterranean lymphoma (MTL) (3 cases). Immunohistological staining of the FCC neoplasms showed that these tumours resembled their European counterpart in that cytoplasmic Ig and J chain could be demonstrated in a proportion of cases. However there was a striking difference in that alpha chain alone, light chain alone, or J chain alone were detected in several cases (in contrast to the predominance of mu plus kappa or lambda light chains found in European cases). Furthermore, prominent intracellular inclusions of alpha chains were found in two cases. Staining of the MTL cases revealed that the characteristic mucosal plasma cell infiltrate was positive for alpha chain (weakly) and J chain (strongly) but that the invasive cells which morphologically resembled FCCs were negative for both constituents. It is argued that these three histological categories constitute the major types of gastrointestinal lymphoma in the Middle East; and that in MTL the invasive lymphoma is of FCC type.