Lymphoma is a systemic tumor of the lymphoid system that can involve multiple anatomic sites. Etiology is often unknown but retroviral infection such as FIV and FeLV can increase risk. The anatomic site of origin is important for prognosis and organ involvement includes gastrointestinal (GI), renal, central nerve system (CNS), nasal, mediastinal, extranodal or multicentric. Renal, CNS, mediastinal, multicentric lymphoma are usually seen in young FeLV-positive cats, and GI and nasal lymphomas are often seen in older FeLV-negative cats. The incidence of FeLV-positive lymphoma continues to decline due to continued vaccination. In this lecture, feline GI lymphoma, the most commonly encountered feline lymphoma recently, will be discussed.

Classification by Clinical and Sonographic Features

The author thinks that feline GI lymphoma is classified into 3 types clinically and ultrasonographically:

1.  Type-1 lymphoma (Figure 1) represents a focal abdominal mass as a result of partially thickened intestine. The mass is usually hypoechoic and has lost the normal layered appearance. The key feature of this type is the thickened intestine is making a mass and intestinal gas can be identified ultrasonographically in the center of the mass. Type-1 lymphoma is typically high-grade (also called large-cell or lymphoblastic) lymphoma and can be diagnosed by cytology in many cases. Surgical intervention can be a treatment option if the mass is localized and the intestine is partially or completely obstructed.

Figure 1. Type-1 lymphoma Thickened intestine is making a mass and it is often palpable.

2.  Type-2 lymphoma (Figure 2) represents a diffuse mild thickening of the muscularis propria layer in the small intestine with or without a jejunal lymphadenopathy. Type-2 lymphoma is difficult to distinguish from inflammatory bowel disease (IBD). Endoscopic biopsy or surgical biopsy is required for definitive diagnosis. Type-2 lymphoma is typically associated with low-grade (also called small-cell or lymphocytic) lymphoma.

Figure 2. Type-2 lymphoma Diffuse and mildly thickened intestine is present. No palpable mass is identified.

3.  Type-3 lymphoma (Figure 3) represents a focal abdominal mass as a result of a jejunal lymphadenopathy with or without intestinal involvement. Although Type-3 lymphoma is similar to Type-1 lymphoma by palpation, Type-3 lymphoma can be distinguished from Type-1 lymphoma by finding the cranial mesenteric artery in the mass by ultrasound. Type-3 lymphoma can be high-grade or low-grade lymphoma. Surgical resection of the enlarged jejunal lymph node is not indicated because the cranial mesenteric artery is almost always involved.

Figure 3. Type-3 lymphoma The jejunal lymph node is enlarged with (right) or (left) intestinal involvement.

Classification by Pathological Features

Feline lymphoma can be classified based on histologic type (primary cell size: small cell vs. large cell), immunophenotype, and architecture. Moore and others have classified feline GI lymphoma into 3 types based on immunophenotype, infiltration patterns with the WHO classification scheme, as well as documenting anatomic location, cell size, presence of epitheliotropism, clonality, and survival data.¹ The mucosal type was defined as a lymphoma confined to the mucosa and lamina propria layers with minimal submucosal extension. The transmural type was defined as a lymphoma with significant extension into the submucosa and muscularis propria layers. The results of the study are summarized in Table 1.

Table 1. Characteristics of feline GI lymphoma

Data modified from Moore PF. Vet Pathol. 2012.

Feline GI lymphoma

Treatment of Feline GI Lymphoma

COP or CHOP based protocols provide extended remission and median survival time ranging from 5 to 8.2 months for high-grade lymphoma. Low-grade GI lymphoma is usually an indolent neoplasm and best treated with oral chlorambucil (4–6 mg/m² PO initially q24h for up to 2 weeks and then q48h) and prednisone (2.5–5 mg/cat q12–24h). Overall response rate for low-grade lymphoma treated with chlorambucil and prednisone was 95% (CR = 56%, PR = 39%) and median survival was 704 days (95% CI: 383–1,237 days).²

Large Granular Lymphocyte Lymphoma (LGL Lymphoma)

This is also known as a tumor of globular leucocyte lymphoma. The neoplastic cells are originated from natural killer (NK) cells or cytotoxic T-cells. LGL lymphomas typically arise in the small intestine and the jejunal lymph node. LGL lymphoma is an aggressive neoplasm and rapidly infiltrates various other organs. Median survival time for cats with LGL lymphoma treated with chemotherapy was 57 days (0–267 days).³ Unfortunately, whatever protocol is selected, the majority of cats will relapse.

Suggested Reading

Vail DM. Feline lymphoma and leukemia. In: Withrow SJ, Vail DM, Page RL, eds. Withrow & MacEwen's Small Animal Clinical Oncology. 5th ed. St. Louis, MO: Elsevier Saunders; 2013.

References

1.  Moore PF, Rodriguez-Bertos A, Kass PH. Feline gastrointestinal lymphoma: mucosal architecture, immunophenotype, and molecular clonality. Vet Pathol. 2012 Jul;49(4):658–668. doi: 10.1177/0300985811404712. Epub 2011 Apr 19.

2.  Kiselow MA, Rassnick KM, McDonough SP, Goldstein RE, Simpson KW, Weinkle TK, Erb HN. Outcome of cats with low-grade lymphocytic lymphoma: 41 cases (1995–2005). J Am Vet Med Assoc. 2008 Feb 1;232(3):405–410. doi: 10.2460/javma.232.3.405.

3.  Krick EL, Little L, Patel R, Shofer FS, Sorenmo K, Clifford CA, Baez JL. Description of clinical and pathological findings, treatment and outcome of feline large granular lymphocyte lymphoma (1996–2004). Vet Comp Oncol. 2008 Jun;6(2):102–110. doi: 10.1111/j.1476-5829.2007.00146.x.