Epitheliotropic T-cell lymphoma

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Generalized distribution of raised plaque overlying scale in abdomen of a dog with mycosis fungoides variant epitheliotrophic lymphoma[1]
Erythema multiforme secondary to epitheliotropic T-cell lymphoma in a Maltese[2]

Epitheliotropic T-cell lymphoma is a variant cutaneous lymphoma of older dogs involving epithelial tissue[3], with a predilection for the buccal cavity and oral commissures.

The disease is characterized by an indolent infiltration of neoplastic lymphocytes in the skin with a specific tropism for the epidermis and adnexal epithelium[4]. Progression of disease may take years in some dogs[5].

Dogs often present with ulcerative stomatitis with no significant or only minor abnormalities on haematology and serum biochemistry panels[6]. The skin shows varying degrees of erythematous, scaly and alopecic macules, patches or plaques. Lymphadenopathy is a rare accompanying presentation. no buccal lesions appear as multifocal flaccid bulla lesions filled with proteinaceous fluid that spontaneously rupture[7].

Diagnosis is usually based on presenting clinical signs and histopathological analysis of biopsied skin. Early-stage epitheliotropic T-cell lymphoma can clinically and histologically mimic a large range of inflammatory dermatoses and exclusion of other diseases is important before establishing a definitive diagnosis.

The histological appearance often takes on the forms of mycosis fungoides, pagetoid reticulosis or Sézary syndrome[8].

Immunohistochemistry is often employed to further characterize the tumor[9] and distinguish it from erythema multiforme, and PCR assays are currently available for detection of T-cell receptor gamma (TCRgamma) rearrangements[10].

A differential diagnosis would include sarcoptic mange, lupus erythematosus, pemphigus, squamous cell carcinoma, drug reactions and food allergy.

Treatment usually requires prednisolone or lomustine (60 mg/m2)[11][12]. Short-term responses are usually noted, but relapses are common after 4 - 6 months.

Buccal forms of this disease can progress rapidly and aggressively, leading to violent, uncontrollable pruritus, which may be disturbing for the owner[13].

The prognosis is considered to be poor, with survival times from few months to 2 years.

Dogs are usually euthanized in cases that progress to high-grade lymphoma or have poor quality of life.

References

  1. Bhang DH et al (2006) Epitheliotropic cutaneous lymphoma (mycosis fungoides) in a dog. J Vet Sci 7(1):97-99
  2. Wikipedia
  3. Moore PF et al (2009) Canine epitheliotropic cutaneous T-cell lymphoma: an investigation of T-cell receptor immunophenotype, lesion topography and molecular clonality. Vet Dermatol 20(5-6):569-576
  4. Chimura N et al (2011) Gene transcription analysis in lesional skin of canine epitheliotropic cutaneous lymphoma using quantitative real-time RT-PCR. Vet Immunol Immunopathol 144(3-4):329-336
  5. Affolter VK et al (2009) Indolent cutaneous T-cell lymphoma presenting as cutaneous lymphocytosis in dogs. Vet Dermatol 20(5-6):577-585
  6. Nemec A et al (2012) Erythema multiforme and epitheliotropic T-cell lymphoma in the oral cavity of dogs: 1989 to 2009. J Small Anim Pract 53(8):445-452
  7. Bizikova P et al (2009) Canine cutaneous epitheliotropic T-cell lymphoma with vesiculobullous lesions resembling human bullous mycosis fungoides. Vet Dermatol 20(4):281-288
  8. Fontaine J et al (2010) Canine cutaneous epitheliotropic T-cell lymphoma: a review of 30 cases. Vet Dermatol 21(3):267-275
  9. Shiomitsu K et al (2012) Cutaneous epitheliotropic lymphoma with dual CD3 and c-kit expression in a dog. Vet Clin Pathol Oct 19
  10. Chaubert P et al (2010) Improved polymerase chain reaction-based method to detect early-stage epitheliotropic T-cell lymphoma (mycosis fungoides) in formalin-fixed, paraffin-embedded skin biopsy specimens of the dog. J Vet Diagn Invest 22(1):20-29
  11. Williams LE et al (2006) CCNU in the treatment of canine epitheliotropic lymphoma. J Vet Intern Med 20(1):136-143
  12. Risbon RE et al (2006) Response of canine cutaneous epitheliotropic lymphoma to lomustine (CCNU): a retrospective study of 46 cases (1999-2004). J Vet Intern Med 20(6):1389-1397
  13. Magnol JP et al (1996) Clinical, morphologic and immunophenotypic data based on 10 cases of canine muco-cutaneous epidermotropic T-lymphoma (analogous to Mycosis Funcgoïde). Important of an animal model of spontaneous pathology. Bull Acad Natl Med 180(2):449-462
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