Intestinal Small Cell Lymphoma: Are Dogs Big Cats?

Abstract

Previously T-cell lymphomas of the gastrointestinal tract in human were classified as enteropathy-associated T-cell lymphoma (EATL) type I and type II. Type I is associated with celiac disease and characterized by large lymphocytes, whereas type II is not associated to enteropathies and characterized by small lymphocytes. In view of these differences, the nomenclature has been changed and EATL currently refers only to type I and type II has been renamed monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL).1 EATL has an aggressive clinical course and tumor cells most commonly have an αβ T-cell receptor phenotype. In comparison MEITL tumour cells express CD8, CD56, and megakaryocyte-associated tyrosine kinase.

T-cell lymphoproliferative disorder (TLPD) is another type of small cell lymphoma described in the intestinal tract. This lymphoma has typically an indolent clinical course and commonly express CD8 and is negative for CD4 and CD56,

Markers of T-cell lymphomas of the gastrointestinal tract have been much less extensively studied in cats and dogs and for this reason for the purpose of this lecture small cell lymphoma (SCL) will be used for neoplastic cells with nuclei smaller than 2 red blood cells in diameter and large cell lymphoma (LCL) for larger neoplastic cells.

SCL characterized by infiltration of the intestinal mucosa by mature T-cells with variable epitheliotropism has been described for more than 10 years in cats. SCL has better outcome than other types of lymphoma in this species, with median survival times over 1.5 years.3 Although criteria have been described in cats to diagnose SCL, these are not as well defined in dogs. However, several recent studies support that SCL is also present in dogs and the clinical findings and outcome will be described in this presentation.