Lymphoproliferativ Lesions of the Orbit and Conjunctiva: Histopathologic Study on 20 cases including 5 cases analyzed by Immunophenotyping

Kim, Chul Woo; Myong, Na Hye; Chi, Je G

Abstract

Lymphoid lesions of the orbit and conjunctiva may be divided histologically into three groups: monomorphous and cytologically atypical malignant lymphomas, benign reactive follicular hyperplasia or inflammatory pseudotumor, and borderline lymphoid lesions mainly composed of small, non-atypical lymphocytes with or without evidence of plasmacytic differentiation or germinal centers which are difficult to clarify its nature by histologic criteria alone. From 1984 to 1992 at Seoul National University Hospital, 20 cases of orbital lymphoid infiltrates were reviewed to find out histopathologic characteristics of malignant lymphomas and try to classify them properly. Also, we sought histologic findings helpful for differential diagnosis between malignant and borderline cases. Histologic examination of malignant lesions usually revealed the features of low-grade B cell lymphomas of mucosa-associated lymphoid tissue(MALT) origin, which predominantly consist of centrocyte-like(CCL) cells. Among 13 primary orbital lymphomas, six cases were classified as MALT lymphomas of Isaacson, six were more apt to be the type of immunocytoma by kiel classification, and remaining one showed mixed pattern of both types in areas. The one case of malignant lymphoma with diffuse large cell type was confirmed by secondary involvement of intestinal lymphoma. Five cases were confirmed by immunoglobulin k-light chain monoclonality on flow cytometry and immunofluorescence study. The histologic findings such as Dutcher bodies, hemosiderin, deposits and polykaryocytes tended to be more frequently encountered in malignant lymphoma rather than indeterminate lesions and were thought to be helpful ones in making differential diagnosis between malignant and benign lesions. With above findings, we assume that the principal neoplastic cells in the low grade lymphoma arising in the orbit and conjunctiva are CCL cells, which might be originated from the localized memory B cells, and also several kinds of B lymphocytes in on-going differentiation stages such as medium-sized monocytoid B cell, lymphoplasmacytoid cell, plasma cell, and mature small lymphocyte also contribute to the tumor progression.