[1565] In-Situ Follicular Lymphoma: A Case Series with Clinical Characterization and Outcome

Monalisa Sur, Ashwyn Rajagopalan, Cathy Ross. McMaster University, Hamilton Regional Laboratory Medicine Program, Hamilton, ON, Canada

Background: Precursor lymphoid lesions have long been recognized in hematopathology. Monoclonal B-cell lymphocytosis has been established as a precursor to CLL, and NK-cell enteropathy was recently identified as a lymphoproliferative disease mimicking NK/T-cell lymphoma in the digestive tract. Neither of these lesions requires treatment in the absence of transformation to a more aggressive form. The entities of in-situ follicular lymphoma and in-situ mantle cell lymphoma are being more frequently recognized in routine surgical practice. As of yet, there is no established guidelines for treatment of these lesions, with most authors advocating a “watchful waiting” approach.
Design: To report ten cases from this institution (from 2005-2011)of incidental in-situ follicular lymphoma. To describe the morphologic, immunohistochemical, and the clinical significance of this diagnosis.
Results: Nine female patients (ages 55-68 years) undergoing surgery with pelvic lymph node dissection (Seven for endometrial carcinoma, two for colonic adhesions for endometriosis) were noted to have the incidental finding of in-situ follicular lymphoma, one had concomittent follicular lymphoma elsewhere. One male patient (age 56 years) was diagnosed on an enlarged unilateral inguinal lymph node removed during surgery for ruptured femoral artery aneurysm.In the cases with pelvic lymph node dissection, one out of several reactive lymph nodes showed in-situ follicular lymphoma in an otherwise reactive lymph node with no architectural effacement. The neoplastic follicles showed expression of B cell and germinal center cell markers with BCL2 staining and a low Ki67 proliferation index in contrast to the reactive follicles which were negative for BCL2 with high proliferation index. Similar findings were noted in the inguinal and mesenteric lymph nodes from the other three patients. Molecular analysis revealed t(14;18) by FISH testing on representative paraffin tissue. Staging bone marrow in these patients was negative. To date, one patient has demonstrated evidence of progression to overt lymphoma. All patients are alive till date.
Conclusions: In-situ follicular lymphoma is often an incidental finding. Recognition of this entity is important, as no further treatment beyond surgical excision is yet recommended. However, long term follow up to better understand the natural history, the significance and the potential for malignant transformation in this group of diseases is needed.
Category: Hematopathology

Monday, March 19, 2012 1:00 PM

Poster Session II # 212, Monday Afternoon


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