Page 713 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 33 Hematopoietic Tumors 691

Nodal Lymphoma
VetBooks.ir 1. Architecture

Diffuse Nodular

2. Cell
Size Large Intermediate Small Intermediate Small

DLBCL LBL BL SLL LPC MZL MCL FL

3. Phenotype

ALT PTCL – NOS TZL

• Fig. 33.3 The histologic approach toward the classification of canine nodal lymphoma. Using excisional
lymph node sections, lymphoma is initially divided into diffuse (effacing) or nodular (noneffacing) forms of
the disease. Next, using a red blood cell or a small lymphocyte as a guideline, the neoplastic population is
divided into large, small, and intermediate forms of the disease. Finally, using knowledge of additional cellu-
lar and nuclear features, including mitotic rate and immunophenotype (B cell, blue boxes; T cell, red boxes),
a final diagnosis is established. ALT, Anaplastic large cell T-cell lymphoma; BL, Burkitt lymphoma; DLBCL,
diffuse large B-cell lymphoma; FL, follicular lymphoma; LBL, lymphoblastic lymphoma; LPC, lymphoplas-
macytoid lymphoma; MCL, mantle cell lymphoma; MZL, marginal zone lymphoma; PTCL, NOS, periph-
eral T-cell lymphoma, not otherwise specified; SLL, small lymphocytic lymphoma; TZL, T-zone lymphoma.
(Reproduced and modified with permission from Seelig DM, Avery AC, Ehrhart EJ, Linden MA. The com-
parative diagnostic features of canine and human lymphoma. Vet Sci. 2016;3(2). Epub 2017/04/25. https://
doi.org/10.3390/vetsci3020011. PubMed PMID: 28435836; PubMed Central PMCID: PMCPMC5397114.)

occasionally other tissues, characterized by a heterogeneous accu- of treatment protocols, better correlation of prognosis with sub-
mulation of lymphocytes (both B and T cell), neutrophils, plasma type, and better comparative capabilities once larger data sets with
cells, and macrophages, often arranged angiocentrically. 90–94 correlate outcomes are generated. Table 33.1 shows some of the
Clinical signs are related to respiratory compromise, and various WHO categories in three different surveys, including a 2-year sur-
chemotherapeutic protocols have been used with reported results vey (2008–2009) of canine necropsy and biopsy cases at the Uni-
varying from rapid progression to long-term clinical remissions. versity of Wisconsin–Madison Veterinary Care Hospital 29,95,96,98 ;
some of the less common categories in the REAL/WHO system
Histologic Classification Systems were not represented and are not listed. Most canine lymphomas
Lymphomas arise from clonal expansion of lymphocytes with fall into the following categories, in decreasing frequency: diffuse
distinctive morphologic and immunophenotypic features. Many large B-cell lymphoma (DLBCL), peripheral T-cell lymphoma
histologic systems have been used to classify NHL in humans, not otherwise specified (PTCL-NOS), T-zone lymphoma (TZL),
and some of these have been applied to lymphoma in the dog and T-lymphoblastic lymphoma (also called “precursor T-cell neopla-
other species. Histologic classification of lymphoma currently fol- sia”), and marginal zone lymphoma (MZL). The REAL/WHO
90
lows the Revised European American Lymphoma/World Health system provides accurate and consistent reproducible diagnostic
Organization (REAL/WHO) system, which incorporates ana- results similar to the system used in human pathology; agreement
tomic, morphologic (cytology and histology), and immunopheno- among a group of pathologists examining 300 cases was 83%, and
typic criteria (B- and T-cell immunophenotype), with the goal of accuracy in evaluating the six most common diagnoses (80% of the
99
enabling accurate and reproducible diagnosis of specific neoplastic cases) was 87%. It is clear that lymphoma is not a single disease,
entities. 90,95,96 Fig. 33.3 represents an overall histologic approach and classification by subtype will become increasingly important
to the classification of various subtypes in the dog as reviewed by as clinical studies are performed to correlate the various catego-
Seelig et al. 96,97 This theoretically should assist in better tailoring ries of disease with biologic behavior, response to treatment, and