Image Quiz: Itchy plaques in a German shepherd

Obtain a fine-needle aspirate of one of the lesions is correct!

A fine-needle aspirate of one of the lesions was collected, air-dried, and stained with a modified Wright's-Giemsa stain. Cytologic examination of the aspirate revealed a collection of relatively mature-appearing, small lymphocytes that were consistent with but not pathognomonic for cutaneous T-cell lymphoma, also known as canine epitheliotropic lymphoma or mycosis fungoides (see below).

A skin biopsy sample was obtained by using a 6-mm punch and submitted for histologic examination, which confirmed the diagnosis. Interestingly, the dog also had a lesion on its cornea (see below), which is uncommon but has been reported.1

In people, mycosis fungoides is a slowly progressive disease that can be present for decades. Treatment is palliative, ranging from topical agents (corticosteroids, chemotherapeutic agents) to oral retinoids (bexarotene) to systemic chemotherapy.2 Phototherapy and total skin electron beam therapy are also used in people. In dogs, CCNU (lomustine) and corticosteroids will frequently result in disease remission for several months. Eventually the dog succumbs to the disease.

There are three stages to the disease in people and dogs. In the earliest stage, patients exhibit exfoliative erythroderma. In dogs, it appears as large sheets of scale lifting off the skin. The next stage is the patch and plaque stage in which the lesions are erythematous, alopecic, and thickened, as in this case. Finally, there is the tumor and nodule stage.

Eventually the disease can metastasize, but many times affected dogs are euthanized because of the numerous ulcerated tumors. In a recent study in 30 dogs with cutaneous epitheliotropic T-cell lymphoma, diffuse erythema was noted in 86.6% with scaling (60%) and focal hypopigmentation (50%).3

REFERENCES

1. Risbon RE, de Lorimier LP, Skorupski K, et al. Response of canine cutaneous epitheliotropic lymphoma to lomustine (CCNU): a retrospective study of 46 cases (1999-2004). J Vet Intern Med 2006;20(6): 1389-1397.

2. Girardi M, Heald PW, Wilson LD. The pathogenesis of mycosis fungoides. N Engl J Med 2004;350 (19):1978-1988.

3. Fontaine J, Heimann M. Day MJ. Canine cutaneous epitheliotropic T-cell lymphoma: a review of 30 cases. Vet Dermatol 2010;21(3):267-275.