Follicular lymphoma with prominent sclerosis ("sclerosing variant of follicular lymphoma") exhibiting a mesenteric bulky mass resembling inflammatory pseudotumor. Report of three cases.

We present three cases of follicular lymphoma (FL) exhibiting prominent sclerosis (sclerosing variant of follicular lymphoma), resembling inflammatory pseudotumor (IPT) of the lymph node, arising from mesenteric lymph node. Clinically all three cases represented bulky masses of the mesenteric lymph node. Histologically, the lesions were characterized by neoplastic lymphoid follicles separated by stromal collagenization and sclerotic process, with cellular infiltrate extending into the adjacent adipose tissue. The lesions contained variable cellular spindle cell proliferation and inflammatory infiltrate including numerous reactive T cells and histiocytes. Small capillary proliferation with vascular change was also noted. Immunohistochemical study demonstrated the myofibroblastic nature of the spindle cells. Moreover, neoplastic follicles were composed of intermediate to medium-sized lymphocytes, somewhat resembling reactive lymphoid aggregates. The overall histomorphological findings of the three lesions were similar to those of IPT of the lymph node. However, CD10, Bcl-2 and Bcl-6 immunostaining demonstrated the neoplastic nature of the lymphoid follicles and the lesions were diagnosed as FL grade 1. The present three cases indicate that the sclerosing variant of grade 1 FL should be added to the differential diagnosis from IPT of the lymph node.