Feline alimentary lymphoma: 2. Further diagnostics, therapy and prognosis

Abstract

Practical relevance: Accurate diagnosis of the distinct subtypes of alimentary lymphoma (AL) that occur in cats is important as there are major differences between them in clinical presentation, treatment and prognosis. Unlike intermediate- and high-grade alimentary lymphoma (I/HGAL) and large granular lymphocyte lymphoma (LGLL), which can often be diagnosed by aspiration cytology, full-thickness intestinal biopsies are usually required for the diagnosis of low-grade alimentary lymphoma (LGAL).

Clinical challenges: LGAL is an increasingly recognised clinical problem and it can be challenging to differentiate from inflammatory disease. Where there is ambiguity on histology, further diagnostics (immunophenotyping and clonality analysis) may be required. The diagnosis of LGLL requires an index of suspicion as it may be missed with routine diagnostics. While cats with LGAL typically achieve durable remissions with oral prednisolone and chlorambucil, I/HGAL runs a more aggressive clinical course and requires multi-agent chemotherapeutic protocols. Information on the treatment of LGLL is limited and this form of AL has the poorest prognosis. Preliminary studies suggest that abdominal irradiation may potentially be of benefit in cats with AL and further investigations are warranted.

Evidence base: The evidence supporting this review is derived from grade II, III and IV prospective studies, retrospective case series, reviews, extrapolation from other species, pathophysiological justification and the combined clinical experience of those working in the field.

Figure 1

Modified Wright-Giemsa stained smear of an ultrasound-guided fine-needle aspirate from the mesenteric lymph node of a cat with low-grade alimentary lymphoma (LGAL). While there is a preponderance of small lymphocytes, it is not possible to distinguish between LGAL and benign lymphoid hyperplasia on cytology. Courtesy of Dr Patricia Martin, Veterinary Pathology Diagnostic Services, University of Sydney

Figure 2

(a) Ileocaecocolic high-grade alimentary lymphoma (HGAL) and (b) a cut surface from the same specimen. Diagnosis of HGAL can often be based on cytology of ultrasound-guided fine-needle aspirates from a focal intestinal mass or an enlarged mesenteric lymph node. (c) Diff Quik cytology of a concurrent abdominal effusion, showing neoplastic round cells and a mitotic figure. Image (c) courtesy of Dr Patricia Martin, Veterinary Pathology Diagnostic Services, University of Sydney

Figure 3

(a) Diff Quik stained smear of a fine-needle aspirate biopsy from an enlarged mesenteric lymph node (b) and intestinal mass (c) in a cat with large granular lymphocyte lymphoma (LGLL). In (a) neoplastic round cells have a basophilic cytoplasm and contain large purple intracytoplasmic granules (arrows). Image (a) courtesy of Dr Patricia Martin, Veterinary Pathology Diagnostic Services, University of Sydney

Figure 4

Histology and immunohistochemistry of intestinal wall biopsies from a cat with B cell HGAL. Heavy infiltration of the lamina propria and submucosa can be seen, destroying the normal architecture of the intestine. Villous and crypt architecture is also severely altered. (a) HE stain; (b) CD3 (T cell marker) stain; (c) CD79a (B cell marker) stain. Note the heavy staining of the neoplastic B cell infiltrate. Courtesy of Associate Professor Mark Krockenberger (image a) and Dr Katherine Briscoe (images b and c), University of Sydney

Figure 5

T cell LGAL. (a,b) HE-stained section of full-thickness intestinal biopsy. There is severe villous blunting and distension. The lamina propria and submucosa are diffusely infiltrated with monomorphous sheets of small lymphocytes. Intraepithelial lymphocytes (IELs) can be difficult to identify in HE-stained sections, but are easily identified in CD3-stained sections (c). This pattern of epitheliotropism with aggregates of neoplastic IELs is common in LGAL and facilitates differentiation from LPE. Courtesy of Associate Professor Mark Krockenberger (image a) and Dr Katherine Briscoe (images b and c), University of Sydney

Figure 6

Rounded, hypoechoic and mildly enlarged (6.3 and 6.5 mm diameter) mesenteric lymph nodes

Figure 7

Thickened jejunal and ileal walls