Photos courtesy John Lewis, VMD, FAVD, Dipl. AVDC The disease covered in this month’s column qualifies as rare. Each year, I see perhaps only two or three cases. However, it’s important to understand, as it can mimic other less serious diseases, often delaying diagnosis. One retrospective study noted that median time between onset and diagnosis was five months.1 However, the clinical characteristics of its oral component are nearly pathognomonic, which help raise suspicion of an insidious disease earlier in the diagnostic process. How Lymphoma Presents When lymphoma occurs in the oral cavity, it is usually a manifestation of cutaneous T-cell lymphoma, often referred to as epitheliotropic lymphoma. One variant is referred to as mycosis fungoides, even though it does not involve fungal disease. When involving the oral cavity, epitheliotropic lymphoma can mimic gingivostomatitis and lip fold dermatitis. When epitheliotropic lymphoma affects the attached gingiva, uniformly bright pink/red gingiva is seen. Conventional gingivitis unrelated to a neoplastic process usually causes erythema only along the free gingival margin. When affected by epitheliotropic lymphoma, the gingiva also often exhibits what appear to be petechiae (Figure 1). However, the change in appearance is not usually limited to the gingiva. Mucosa often looks either very pink/red, or if originally pigmented, the mucosa becomes depigmented. This depigmentation also may involve the nasal planum and pigmented skin of the lips (Figure 1). The commissures and the skin around the mucocutaneous junctions also may be involved (Figure 2). Figure 2: Epitheliotropic lymphoma in a different golden retriever. Note the severe erythema of the gingiva and severe changes at the mucocutaneous junctions. One retrospective study of 30 cases found that skin was uniformly involved and 50 percent of cases showed involvement of mucocutaneous junctions.1 The cases I’ve seen had no discernible skin involvement except for skin at the mucocutaneous junctions of the mouth, but this may be a reflection of which cases seek out dentists in comparison to those that see dermatologists. Who It Affects Breed predilection may include the bichon frise, as the breed represented five of 30 cases in one retrospective study.1 The breed that I’ve seen most commonly affected is the golden retriever (Figures 1, 2). Epitheliotropic T-cell lymphoma also can be seen in cats.3 It affects older cats with no apparent sex or breed predisposition. One retrospective study of lesions showed erythematous plaques or patches, scaly alopecic patches and nonhealing ulcers or nodules, which sometimes mimicked an eosinophilic plaque. Pruritus was rare. No lesions affecting the oral mucosa were observed.3 Clinical diagnosis tends to be more challenging in cats than in dogs. As in dogs, final diagnosis must be based on histopathological examination of biopsy samples. Figure 3 shows an example of a cat with epitheliotropic lymphoma affecting the right upper lip and right lower eyelid. Figure 3: Cutaneous T-cell lymphoma affecting the right upper lip and right lower eyelid in a 14-year-old domestic shorthair cat. Unfortunately, survival times with canine epitheliotropic lymphoma are not long. In one study, the median survival time after diagnosis was six months, with a range of three months to two years, and this did not change appreciably with treatment.1 The survival time of cats seems to be more variable than that of dogs. A Different Prognosis A stark contrast from the prognosis of epitheliotropic T-cell lymphoma, low-grade indolent T-cell lymphomas comprise up to 29 percent of all canine lymphoma. A subtype of indolent lymphoma, T-zone lymphoma, represents 61.7 percent of indolent lymphomas. T-zone lymphoma may occur in the oral cavity, as seen in the tounge of a Jack Russell terrier seen in Figure 4. T-zone lymphoma’s overall media survival time was shown to be nearly three years in one study.4 T-zone lymphoma may occur in the oral cavity, as seen in the tongue of a Jack Russell terrier seen in Figure 4. T-zone lymphoma’s overall median survival time was shown to be nearly three years in one study.4 Figure 4: T-zone lymphoma affecting the caudodorsal tongue in a 10-year-old Jack Russell terrier. This patient was diagnosed in 2014 and is still doing very well. Practitioners see diffuse oral inflammation frequently, often daily. Though most cases will be due to a benign process, keep the “zebra” diagnosis of lymphoma in mind next time you see an odd manifestation of oral inflammation or depigmentation. It is always a good idea to biopsy an area of persistent oral inflammation References Fontaine J, Heimann M, Day MJ. “Canine cutaneous epitheliotropic T-cell lymphoma: a review of 30 cases.” Vet Dermatol 2010; 21(3): 267-275. Fontaine J, Bovens C, Bettenay S, Mueller RS. “Canine cutaneous epitheliotropic T-cell lymphoma: a review.” Vet Comp Oncol 2009; 7(1): 1-14. Fontaine J, Heimann M, Day MJ. “Cutaneous epitheliotropic T-cell lymphoma in the cat: a review of the literature and five new cases.” Vet Dermatol 2011; 22(5): 454-61. Flood-Knapik KE, Durham AC, Gregor TP, et al. “Clinical, histopathological and immunohistochemical characterization of canine indolent lymphoma.” Vet Comp Oncol 2013; 11(4): 272-286. Dr. John Lewis practices veterinary dentistry and oral surgery at NorthStar VETS in Robbinsville, N.J.
