Composite Small Lymphocytic Lymphoma/Chronic Lymphocytic Leukemia and Follicular Lymphoma: A Clinicopathological Study of Six Cases

Background: Composite small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) and follicular lymphoma (FL) is extremely rare, and only 13 cases have been reported previously. Methods: We identified 6 cases of composite SLL/CLL and FL in our database and studied their clinical, histologic, immunophenotypic, and cytogenetic features. A literature review of the existing cases was also conducted. Results: The patients included 4 males and 2 females, with a median age of 72 years. Four patients presented with lymphadenopathy and 2 with extranodal diseases. Lymphocytosis was seen in 2 cases. Serum lactate dehydrogenase levels were within normal range in all but one case. There were 2 histologic patterns: SLL/CLL predominant pattern (type I) and FL predominant or mixed pattern (type II). The type I pattern was exclusively associated with in situ follicular neoplasia (ISFN). The SLL/CLL showed typical morphology and immunophenotype in all the cases. The FL component included low grade (n = 3), ISFN (n = 2), and primary cutaneous FL (n = 1). Four cases had staging bone marrow biopsies including 3 cases with involvement by SLL/CLL and 1 case with involvement by SLL/CLL and FL. Four patients received treatments, one was under clinical surveillance, and one had no available information. All patients were alive after a median follow-up of 22 months. Conclusions: This is the largest case serial of composite SLL/CLL and FL. The CL affects elderly individuals, presents with advanced clinical stage, and appears to have a relatively indolent clinical course.