Follicular Lymphoma of the GI Tract - Distinct Entity or Extranodal Manifestation of Nodal Disease?.

Introduction: Primary GI follicular lymphoma is a rare, poorly studied entity. Current discussions in the literature debate whether or not it is a distinct extranodal entity, similar to cutaneous follicle center lymphoma. Like cutaneous follicle center lymphoma, it appears to have a good prognosis and low incidence of t(14;18).

Case History: This is a 74 year old white male who presented for routine screening colonoscopy in May 2003. On evaluation the patient was found to have nodularity of the colon. Biopsies demonstrated several submucosal and mucosal follicles with no distinct mantle zones, composed of a uniform population of centrocytes. No lymphoepithelial lesions or plasma cells were identified. These cells proved to be monoclonal B cells, with a phenotype of CD20+, CD10−/+, bcl-2+/−, bcl-6+, CD5−, CD43−, lambda+ and t(14;18) negative. CD21 stain highlighted the underlying follicular dendritic architecture. No adenopathy was noted at this time. A diagnosis of B cell lymphoma, consistent with extranodal follicular lymphoma, grade I was rendered. As the patient was otherwise asymptomatic, no treatment was given. Four months later, the patient developed retroperitoneal adenopathy and a large pelvic mass. A lymph node biopsy demonstrated numerous large follicles composed of a uniform population of centrocytes, with attenuated to absent mantle zones. The cells were CD20+, CD10+, bcl-2+, lambda+ and t(14;18) positive. There was a comcomitant transitional cell carcinoma of the urinary bladder, which required radical cystectomy. The patient was then initiated on chemotherapy with CVP, for three cycles. He was followed without treatment for 2 years when he developed a tonsillar mass. A biopsy demonstrated a CD10+ diffuse large B-cell lymphoma. Cytogenetic analysis revealed a complex karyotype with a t(14;18). The patient underwent a staging bone marrow, which was positive for follicular lymphoma. The cells were CD20+, CD10−/+, bcl-6+, lambda+, and t(14;18) negative. He was then started on R-CHOP for his B symptoms and extensive adenopathy, and is currently 2 months into therapy.

Discussion: This is an unusual case of almost concomitant presentation of t(14;18) negative extranodal follicular lymphoma of the GI tract and classical t(14;18) positive nodal follicular lymphoma. Possible explanations include that these are two manifestations of the same disease, two separate diseases coincidentally occurring around the same time, or a follicular lymphoma clone which has evolved into nodal and extranodal entities.