Primary Colorectal Follicular Lymphoma in 3 Dogs

Primary colorectal follicular lymphomas are rare indolent lymphoid neoplasms in humans that have not been reported in dogs. We describe 3 cases of primary colorectal follicular lymphoma in dogs with histologic and immunohistochemical features similar to their human counterpart. Initial clinical signs in all dogs included tenesmus, hematochezia, and a palpable rectal mass. Two dogs were castrated males and 1 an intact female, between 9 months and 2 years of age, and of varied breeds. All 3 cases of colorectal follicular lymphoma were characterized by proliferation of follicular germinal centers with no polarity or mantle zone and were composed of centrocytes admixed with fewer centroblasts. By immunohistochemistry, lymphoid cells expressed CD20, BCL2, and BCL6 and lacked expression of CD3, CD5, and cyclin D1. Polymerase chain reaction for rearrangements of the immunoglobulin heavy chain confirmed a monoclonal population in all cases. In 2 of the 3 cases, a solitary nodular colorectal mass was excised and appeared curative; however, the third case had multiple colorectal masses and the animal developed multicentric lymphoma. This case series immunohistochemically characterizes and distinguishes colorectal follicular lymphoma from atypical lymphoid hyperplasia.

Severe Gastritis Secondary to Epstein-Barr Viral Infection

Infectious mononucleosis is usually a self-limited clinical syndrome caused by primary Epstein-Barr virus infection. It is occasionally compounded by severe complications involving many different organ systems. Predominant gastrointestinal involvement is rarely documented. We present an unusual case of acute Epstein-Barr virus infection–associated gastritis with diffuse atypical lymphoid hyperplasia in gastric mucosa. The clinical, radiographic, histopathologic, immunohistochemical, and in situ hybridization features needed for accurate diagnosis and differentiation from gastric malignancies are discussed.