Confocal laser scanning analysis of an equine oral mast cell tumor with atypical expression of tyrosine kinase receptor C-KIT.

The research discusses a rare incidence of an oral mast cell tumor in a horse that expressed an atypical form of the tyrosine kinase receptor C-KIT. Using confocal laser scanning microscopy, the study identified an unusual location of the C-KIT receptors in the cell’s Golgi apparatus, which suggests a potential processing error within the tumor’s cells.

Introduction

• This study revolves around a case of a 20-year-old female horse that developed an oral mast cell tumor characterized by an unusual receptor expression.
• The mast cell tumor was nodular, firm and focally ulcerated, located at the right dorsobuccal face of the horse’s tongue.

Research Findings

• The histological examination of the nonencapsulated tumor uncovered that it was composed of well-differentiated mast cells which positively reacted to Cresyl Violet – a stain used in histology to reveal cellular components.
• The mast cells were found in dense aggregates infiltrating the tissue and were accompanied by a large number of eosinophils – a type of white blood cell commonly associated with allergic reactions and inflammation.
• Immunohistochemical analysis, a method used to visually detect the presence of specific proteins in tissues, showed that the cells within the tumor had a strong intracytoplasmic signal for tryptase – an enzyme predominantly used by mast cells, and a faint membrane-associated and perinuclear signal for the tyrosine kinase receptor KIT – a type of protein that regulates cell functions such as growth and division.

Implications of Atypical C-KIT Expression

• Confocal laser scanning microscopy verified a spatial colocalization of the KIT protein in the Golgi apparatus of the cells, which is an unconventional location for this receptor. The Golgi apparatus is a cell organelle that processes and packages proteins, thus its association with KIT signals to a potential defective protein processing within the tumor cells.
• This unusual distribution of tyrosine kinase receptor C-KIT may be responsible for the tumor formation in the horse, and could potentially highlight new insights into the biology of oral mast cells tumors in equines.
• Despite the presence of the tumor, the study indicated that it did not lead to a poor prognosis for the horse.