Extra-nodal subcutaneous Hodgkin's-like lymphoma and subsequent regression in a cat

Abstract

Hodgkin's-like lymphoma is a slow growing neoplasm, usually affecting the lymph nodes of the head and neck, which has been sporadically described in veterinary patients. This report describes the clinical and histopathological features in a 9-year-old male neutered Siamese cat that presented with a 6 week history of mid-dorsocranial swelling. Immunohistochemistry demonstrated positive staining for CD79a, paired box protein and B lymphocyte antigen-36, with variable, weak-to-moderate cytoplasmic staining for human leukocyte antigen-DR and CD18, and negative staining for antimacrophage antibody. The diagnosis based on incisional biopsy was Hodgkin's-like lymphoma; however, no evidence of neoplasia was found following wide surgical excision. This case report demonstrates two unreported items of note: the novel extranodal site of Hodgkin's-like lymphoma in a cat and tumour regression following initial biopsy. It is hypothesised that the surgical trauma of biopsying the lesion or the introduction of foreign material may have caused the regression of the neoplastic cells through induction of an anti-tumour immune or inflammatory response.

Figure 1

Presurgical resection with the mass outlined for surgical planning. The mass measured approximately 20 mm × 10 mm

Figure 2

Picture taken prior to suture removal 21 days postsurgical resection

Figure 3

Haematoxylin and eosin section at high power (x 400) demonstrating the neoplastic cells (arrowed) from the initial wedge biopsy. Larger arrows indicate neoplastic cells. Smaller arrows indicate clusters of small reactive lymphocytes

Figure 4

Immunohistochemistry demonstrating the atypical cells (arrowed) staining positive for CD79a (B-cell marker) from the initial wedge biopsy

Figure 5

Immunohistochemistry demonstrating the atypical cells (arrowed) staining positive for paired box protein (B-cell marker) from the initial wedge biopsy. Small arrows indicate positively staining neoplastic cell nuclei. Larger arrows highlight a cluster of reactive small B lymphocytes

Figure 6

Immunohistochemistry demonstrating the atypical cells staining positive for B lymphocyte antigen (B-cell marker) from the initial wedge biopsy