A 9-year-old, spayed female Golden Retriever dog showed lymphocytosis and lymphadenopathy, secondary to suspected chronic lymphocytic leukemia (CLL). Small-to-intermediate lymphocytes were observed from the cytological examination of the right popliteal lymph node via a fine-needle aspirate.
The dog was suspected to have a low-grade lymphoma based on the finding of cytology. Also, ultrasonography reveled thickened lesions in the stomach and small intestine. Histopathology of the popliteal lymph node and small intestine revealed a simultaneous presence of T-zone lymphoma (TZL) and high-grade gastrointestinal (GI) cytotoxic T-cell lymphoma. PCR for antigen receptor rearrangements assay suggested that both lymphomas, though both originated in the T-cells, derived from different genes. The dog died 15 days after diagnosis, despite chemotherapy.
A–C: Cytological images on day 1. (A) Peripheral blood smear. Increased numbers of small lymphocytes. (B) Cytology of the popliteal lymph node biopsy. Most lymphocytes are small-to-intermediate, mature lymphocytes. Some lymphocytes show a “hand mirror” type of cytoplasmic extension (arrowhead) (Wright-Giemsa stain, × 400). (C) Slide preparation of tissue from the small intestine. The lymphocytes are intermediate-to-large, immature cells, and some display azurophilic granules in the cytoplasm (LGLs, arrowhead). D–F: Histological images of popliteal lymph node tissue. (D) Hematoxylin and eosin (H&E) staining. (E) The lymphocytes with fading follicular structures are CD20 positive (asterisk). Immunolabeling with anti-CD20, a hematoxylin counterstain. (F) The nodal capsule (CD3 positive) is thinned without the involvement of the perinodal tissue (asterisk). Immunolabeling with anti-CD3, hematoxylin counterstain. G–I: Histological images of the intestinal tissue. All lymphocytes are positive for CD20 (G), CD3 (H) and granzyme B (I).
(A) Transverse ultrasound image on day 1 showing a thickened intestinal wall (approximately 9.0 mm, arrowhead). (B) Post-contrast transverse CT image on day 2 also showing a thickened intestinal wall (arrowheads). The intrathoracic and abdominal lymph nodes are enlarged.
PARR analysis. (A) The peripheral blood sample shows TCRγ gene rearrangement. (B) The intestinal tissue sample also shows TCRγ gene rearrangement. The two tumors demonstrate clonal expansions from different primers.