T cell-rich B cell lymphosarcoma in the tongue of a horse.

The article focuses on a rare case of lymphosarcoma that developed in a horse’s tongue and spread to nearby lymph nodes. The study highlights the composition of the tumor as T cell-rich B cell lymphosarcoma.

Background of Lymphosarcoma in Horses

• Lymphosarcoma, the most common tumor in the equine haemopoietic system, is typically seen in horses aged between five and ten years.
• There are four recognized types of this disease: multicentric, thymic, alimentary, and cutaneous, with the multicentric form being the most common.
• The prognosis is usually poor, except for cutaneous lymphosarcoma that often has a prolonged clinical course and responds well to treatment.
• Other reported primary sites for the lymphosarcoma include the palatine tissues, spleen, meninges, and urinary bladder.

Case Description

• The paper focuses on a Shetland pony mare that showed symptoms of nasal discharge containing food material for a month, as well as nasopharyngeal collapse causing larynx and oesophagus obstruction.
• An oral examination revealed a mass in the back part of the left side oropharynx. The enlarged submandibular lymph nodes revealed neoplastic mass composed of variant lymphoid cells, which led to the diagnosis of lymphosarcoma.
• Due to the condition, the horse was euthanized and subsequent postmortem examination found significant abnormalities in the oropharyngeal region. A mass was observed at the base of the tongue and along with that, enlargement of the left retropharyngeal lymph node.
• The bone marrow seemed fatty and inactive, giving no gross evidence of lymphadenopathy elsewhere in the body.

Investigation and Findings

• On histological examination, there was a clear invasion by a diverse population of lymphocytes. The presence of lymphoid cells, cells with larger oval and pale staining nuclei, and some histiocytic cells highlighted the heterogeneity of the tumor.
• The retropharyngeal nodes showed similar invasion with almost complete replacement by neoplastic lymphoid cells. But, there were no significant pathology identified in the other examined organs, including the peripheral and deep lymph nodes.
• The primary tumor and the retropharyngeal node were studied by immunohistochemistry, confirming the phenotypes of the cells involved in the tumor which designated it as a T cell-rich B cell lymphosarcoma.