chapter
24
Epitheliotropic
(Cutaneous) Lymphoma
DEFINITION/OVERVIEW
Cutaneous T-cell lymphoma (CTCL), both epitheliotropic and nonepitheliotrophic,
is an uncommon cutaneous neoplasia affecting many species, including dogs and cats.
Heterogeneous group of diseases with a prevalence of less than 1% of skin tumors in
dogs.
The majority of CTCL cases are epitheliotropic (CEL) characterized by infiltration of
the epidermis and adnexal structures with malignant T cells.
ETIOLOGY/PATHOPHYSIOLOGY
Cutaneous nonepitheliotrophic lymphoma (CnEL): caused by either B cells or T cells;
more often T cell in cats.
Most often associated with CD3+lymphocytes.
CnEL: large cell lymphoma characterized by infiltration of the dermis and subcutis
with heterogeneous groups of malignant cells; may be associated with FeLV in cats.
Cutaneous epitheliotropic lymphoma, or “classic” MF (mycosis fungoides): most
common T cell lymphoma in dogs.
Caused by epitheliotropic gamma delta T cells in 70% of cases (100% in pagetoid
form).
Most often associated with CD4−/CD8+cytotoxic T cells: differs from disease of
human beings (predominantly CD4+/CD8−helper T cells).
COX-2 is not expressed by neoplastic infiltrates in CEL; differs from disease in human
beings (significant expression of COX-2 by neoplastic lymphocytes).
In one study, dogs with atopic dermatitis were at 12 times higher risk of developing
CEL than dogs without atopic dermatitis.
Allergic skin disease producing chronic T cell activation and proliferation leading to
clonal expansion of neoplastic cells may be a cause; initial lesions often develop in
areas associated with atopic dermatitis.Peripheral lymphocytes with skin-homing receptors may be preferentially
sequestered in skin lesions.
Spread of malignant cells to lymph nodes and organs occurs in the late tumor stage.
Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Dermatology, Third Edition.
Karen Helton Rhodes and Alexander H. Werner.
©2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc.
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