Dear Editor, Richter's transformation occurs in 2–8% of patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and usually involves transformation to diffuse large B-cell lymphoma (DLBCL) or rarely (0.4% of cases) Hodgkin lymphoma [1]. Both transformations may involve nodal or extranodal sites and both could locate in separate or in the same tissue (composite lymphoma). Molecular and immunophenotypic evidence indicates that the transformed cells usually, but not always, derive from the same clone as the original CLL/SLL [1, 2]. The vermiform appendix, naturally rich in gut-associated lymphatic tissue, is often involved in patients with nonHodgkin lymphoma. However, there have been only 13 cases of classical Hodgkin lymphoma and 1 of nodular lymphocyte-predominant Hodgkin lymphoma reported in the appendix [3–5]. To our knowledge, a composite CLL/ SLL with Hodgkin transformation heralded by acute appendicitis has not been reported. Here, we document this rare case below. A 64-year-old woman presented to our facility with bilateral axillary adenopathy and splenomegaly and was subsequently diagnosed with CLL/SLL. Sixteen months after this initial diagnosis, she presented with acute appendicitis. The appendectomy specimen showed acute serositis associated with two zonal atypical lymphoid infiltrates composed of: (1) a monotonous population of small, mature lymphoid cells with clumped nuclei and scant cytoplasm that expanded the lamina propria (Fig. 1a 1 and 2) and (2) multiple nodular proliferations consisting of numerous Reed-Sternberg (RS)like cells or Hodgkin cell variants in a matrix of polymorphous inflammatory cells, including predominantly histiocytes, small lymphocytes, and few granulocytes throughout the wall of the appendix (Fig. 1c 1 and 2). Immunohistochemical stains and in situ hybridization demonstrated two distinct phenotypic features: (1) PAX5+/CD5+/ CD23+/cyclin D1-neoplastic B cells, compatible with SLL (Fig. 1b 1 and 2) and (2) CD30+/CD15+/CD45-/ EBER+atypical large cells, compatible with classical Hodgkin lymphoma (Fig. 1d 1 and 2). Immunostains also confirmed that the small lymphocytes surrounding the RSlike cells were T cells. According to the literature, the infiltrate distribution is consistent with so-called type 2 transformation, where the RS-like cells are found in a polymorphous inflammatory background, characteristic of primary classical Hodgkin lymphoma, and separate from SLL cells. In contrast, in type 1 transformation, the RSlike cells are distributed among clonal B cells, that is, SLL cells [1]. The patient received a matched related peripheral blood stem-cell transplant 21 months after her initial diagnosis. Although Hodgkin lymphoma is among the most common malignancies to secondarily involve patients with CLL/SLL [6], Hodgkin transformation of CLL/SLL is a B. Quigley (*) Department of Pathology and Cell Biology, University of South Florida College of Medicine, 4105 W Coachman Ave, Tampa, FL 33611, USA e-mail: bquigley@health.usf.edu