Primary splenic lymphoma in a horse.

This research article revolves around a unique case of primary splenic lymphoma in a 4-year-old Thoroughbred stallion. Despite the lymphoma’s high mitotic index, the growth was not invasive and there was no evidence of metastasis.

Key Findings

• The horse had a solitary splenic mass. The mass was well-delineated and measured 20 x 20 x 15 cm. It had hemorrhagic and necrotic foci within it.
• Upon histological examination, it was found that the mass was composed of lymphoma cells of the diffuse large non-cleaved type. These cells had a high mitotic index and were scattered among macrophages, which collectively created a “starry sky” pattern.
• The lymphoma cells showed positivity for various substances. They tested diffuse positivity for acid phosphatase and alpha naphthyl butyrate esterase. Additionally, they tested positive for intracytoplasmic IgM, albeit occasionally. However, they were primarily positive for proliferating cell nuclear antigen.
• At the ultrastructural level, the lymphoma cells exhibited moderately-developed rough endoplasmic reticulum with occasional dilation of the cisternae.

Diagnosis

• Based on the collective findings, a diagnosis of primary splenic lymphoma of B cell origin was made.

Unresolved Questions

• The research article concluded on an ambiguous note as the reason behind the absence of invasive growth or metastasis, despite the high proliferation activity of the lymphoma, was unclear.

Implications

• The study highlights an unusual occurrence of a solitary splenic lymphoma without any invasive growth or metastasis, despite the cells’ high proliferative activity.
• The findings, particularly the characteristics of the lymphoma cells, could prove useful in further research or when diagnosing other cases of lymphoma in horses.