Malignant retroperitoneal paraganglial tumour in a cow.

A large primary retroperitoneal sublumbar neoplasm was identified in an 11-year-old Holstein cow, with metastases to the lungs, kidneys and lymph nodes. The tumour cells proliferated in a characteristic endocrine pattern, were argyrophilic and positive for neuron-specific enolase, and had membrane-bounded intracytoplasmic granules. In addition, the cells were occasionally positive for cytokeratin and had desmosome-like intercellular junctions. The primary tumour mass was diagnosed as a malignant paraganglial tumour of the aortico-sympathetic ganglion (organ of Zuckerkandl), and was considered to contain primitive cells with epithelial differentiation.