22. Sclerosing variant of follicular lymphoma exhibiting a mesentric mass resembling inflammatory psuedotumour; a distinct entity

Abstract

Some degree of sclerosis is common in follicular lymphoma, particularly in those involving the retroperitoneum and groin; however, the term ‘sclerosing variant of follicular lymphoma’ is applied when the sclerosis is prominent. We report an extremely rare case of follicular lymphoma with prominent sclerosis resembling inflammatory pseudotumour (IPT) of the lymph node from a 67-year-old man. Clinically he presented with the mesenteric lymphadenopathy. Histologic examination revealed a patchy and dense lymphoid infiltrate associated with complete disruption of the nodal architecture with extensive sclerosis by bands of collagen subdividing the infiltrate. The infiltrate consists predominantly of lymphocytes and includes a population of small lymphocytes, with irregular, convoluted nuclei, together with larger lymphoid cells with oval nuclei, more vesicular chromatin, small prominent nucleoli and rim of pale cytoplasm. In some areas, the lymphoid elements show a suggestion of a follicular arrangement. There was no evidence of residual lymph node and the process showed extracapsular extension into the adjacent fatty tissue. The lymphoid cells showed positive immunoreactivity for B-cell markers with co-expression of CD20, Cd79a, CD10 and Bcl2. Flow cytometry also confirmed the presence of a monoclonal population of B-cells consistent with a B-cell non-Hodgkin lymphoma. The overall features were interpreted as diffuse large B-cell lymphoma arising within a grade 1 follicular lymphoma with prominent sclerosis. There are only three cases of sclerosing variant of follicular lymphoma resembling IPT reported in the literature. This case emphasises the importance of considering the sclerosing variants of follicular lymphoma as a differential diagnosis of IPT of the lymph node.