Small Animal Dermatology, 3rd edition

368 DISEASES/DISORDERS

DIAGNOSTICS

 Laboratory abnormalities: vary depending on the stage and form of cutaneous T cell

lymphoma, and whether disease has disseminated.

 S ́ezary cells: small (8–20μm) neoplastic lymphocytes with convoluted nucleus and

cerebriform appearance are present in peripheral blood of patients with Sezary syn- ́

drome.

 Flow cytometry for detection of T cell lineages in blood.

 Generally unremarkable if only the skin or mucosa is affected.

 Radiographs and ultrasound: not commonly used in the early stages; imaging is even-

tually necessary to confirm systemic disease and/or for tumor staging.

Diagnostic Procedures

 Skin scrapings and fungal culture: rule out demodicosis and dermatophytosis, if appli-

cable.

 Cytology: increased numbers of atypical lymphocytes with large and infolded nuclei

(Figure 24.16).

 Skin biopsy: definitive diagnosis; sample multiple different-appearing lesions, avoid

eroded/ulcerated and infected lesions.

Pathologic Findings

 CnEL:
Sheets of neoplastic lymphocytes produce diffuse and dense invasion of the der-

mis and subcutaneous tissues

Infiltration of the epidermis is lacking.

 CEL:
Hallmark finding: trophism of neoplastic cells for the epithelium (epidermal and

mucosal)

Infiltrate of neoplastic lymphocytes: into epidermis and epithelium of hair fol-

licles and adnexal structures; distributed diffusely or clustered together to form

discrete Pautrier microaggregates within the epithelium

Follicular and adnexal structures can be obliterated by infiltrate

Keratinocyte apoptosis may be mild to marked

Interface dermatitis mimics inflammatory processes in early stages; CEL may be

difficult to distinguish from reactive lymphocytic inflammation; reactive lym-

phocytes migrate throughout the epidermis and are associated with spongiosis

whereas neoplastic lymphocytes tend to accumulate in the lower portion of the

epidermis

Dermal-epidermal junction becomes obscured by neoplastic lymphocytes in

later stages

Tumor cells are typically larger than normal with infolded nuclei and increased

cytoplasm