Presentation of malignant lymphoma in the rectum.

Because of their rarity, rectal malignant lymphomas are generally included in the group of large intestine lymphomas. A study of eight cases of rectal lymphomas revealed distinctive clinicopathologic correlations. Using the Lukes-Collins classification of malignant lymphomas, the authors interpreted all the cases as B-cell lymphomas, supported by immunologic studies in four cases. Seven cases were classified diffuse follicular center cell (FCC) lymphomas; four as small cleaved FCC; and three as small noncleaved FCC. One case was interpreted as plasmacytoid lymphocytic lymphoma. Monoclonality was demonstrated by immunoperoxidase staining of cytoplasmic immunoglobulin in three cases and by immunologic surface marker studies in another case . The small noncleaved follicular center cell lymphomas presented as localized tumors (clinical Stage I), so-called primary lymphomas. The small cleaved follicular center cell lymphomas, by contrast, were part of a generalized lymphomatous process in three of the four cass with demonstrated involvement of the gastrointestinal tract elsewhere in two cases.