Table 13-7.

Common Lymphoma Diagnoses in Domestic Animals Using the WHO Classification System

Lymphoma Subtype	Pattern	Cell Size	Grade	Postulated Normal Cell Counterpart	Defining Histopathologic Features
DLBCL	Diffuse	Large	Mid to high	Germinal center or post–germinal center (activated) B lymphocyte	Multiple nucleoli (centroblastic variant) or single central nucleoli (immunoblastic variant)
PTCL	Diffuse	Large	Mid to high	Activated mature T lymphocyte	Nuclei of variable size and shape; eosinophils may be present
Burkitt-like lymphoma	Diffuse	Intermediate	High	Either germinal center or post–germinal center (activated) B lymphocyte	Uniform nuclear size with multiple distinct small nucleoli; numerous tingible body macrophages
T-LBL	Diffuse	Intermediate	High	Naïve T lymphocyte	Dispersed chromatin that obscures nuclear detail
TZL	Nodular	Small to intermediate	Indolent	Activated mature T lymphocyte; paracortical	Abundant clear cytoplasm, sharp shallow nuclear indentations; expansion of paracortex with peripheralization of “fading” follicles
MZL	Nodular	Intermediate	Indolent	Post–germinal center marginal zone B lymphocyte	Prominent single central nucleoli; expansion of marginal zone with encircling of “fading” follicles
TCRLBCL	Nodular/diffuse	Large	Indolent to low	Germinal center B lymphocyte	Large irregularly-shaped nuclei with 1-2 prominent nucleoli; numerous small reactive T lymphocytes
EATCL	Diffuse	Small to intermediate	Low	Intestinal intraepithelial T lymphocytes	Hyperchromatic nuclei with dispersed chromatin

DLBCL, Diffuse large B cell lymphoma; EATCL, enteropathy-associated T cell lymphoma; MZL, marginal zone lymphoma; PTCL, peripheral T cell lymphoma; TCRLBCL, T cell–rich large B cell lymphoma; T-LBL, T cell lymphoblastic lymphoma; TZL, T zone lymphoma, WHO, World Health Organization.