Neurofibromata are tumour like manifestations produced by the diffuse overgrowth or dysplasia of the nerve sheaths and their supporting connective tissue, which leads to an expansion of the parent nerve with consequent distortion of its nerve bundles and their neuroaxons. Both the Schwanatan elements and the fibroblastic cells of the endoneurium and perineurium take part in the tissue proliferation.
Neurofibromata are not infrequently found in cattle slaughtered at abattoirs. The present study indicates that either the disease is more prevalent than commonly supposed or that the incidence is increasing in New South Wales. Some 110 cases have been examined in a period of three months and others have been reported from country abattoirs.
LOCATION OF TUMOUR
The tumours occurred most frequently in the superficial nerves of the ventricles of the heart, around the aorta from the base of the heart onwards for considerable distances, in the brachial plexus and its branches and in the thoracic nerves including the intercostals. Lesions have also been found involving intra-abdominal nerves, lumbosacral plexus as well as cervical nerves, ganglia and plexuses, nerves of the striated muscles including the tongue. Skin lesions similar to those seen in neurofibromatosis (van Recklinghausen's disease) in man were encountered in a 6 year old Hereford cow.
Due to the thorough examination of the heart in meat inspection for tapeworm cysts, it is likely that a higher percentage of cases involving this organ would be found than in the brachial plexus or musculature, where great care has to be taken not to disfigure areas from which the commercial cuts of meat are derived. A statistical evaluation of this tumour in regard to either incidence or location would therefore be difficult to obtain.
These tumours produce tortuous and nodular enlargements of the nerves. The nodular or knotty thickening of the nerve is often shiny or glistening. Other tumours, usually encapsulated, when attached to or replacing portion of a nerve were greyish white firm neoplasms with areas of softening and liquefaction. Many of the tumour masses in the heart, mediastinum and abdomen were soft, greyish tumours and were thinly encapsulated or non-encapsulated. On section, they were often lobulated and frequently a lobule or an entire lesion would have a slightly gelatinous consistency. Areas of haemorrhage, necrosis and mucoid change occasionally gave the tumours a mottled appearance.
The tumour cells were elongated and spindle shaped with oval or long cylindrical nuclei. Distinct palisading of the nuclei in some tumours as well as the characteristic alignment of cells in interlacing bundles and whorls. Intercellular fibres similar to a fine reticulum or to connective tissue collagen (in the more solid or compactly organised tumour) were present. In many of the tumours studied, the whorling and palisading were not seen, instead a more diffuse and haphazard arrangement of Schwann cells, connective tissue elements and isolated neurites. Areas of necrosis, haemorrhage, mucoid degeneration and infiltration with lymphocytes were observed in some of the tumours examined.
The lesions grow slowly as indicated by a very low mitotic rate but may reach large proportions as shown in the illustrations (Kodachrome transparencies).
The majority of cases of neurofibromata in cattle are detected at slaughter. Specific clinical signs of neurofibromata are not yet determined. Because of the location of tumour masses on the nerve trunks in the thoracic cavity, namely cardiac,recurrent laryngeal vagus and intercostals, abnormal functions of cardiac and respiratory systems could be expected. Cardiac arrythmias as well as inspiratory dyspnea which remain undiagnosed following detailed clinical examination would be suspicious symptoms of neurofibroma.
The tumours are seen quite often in the nerves of the brachial plexus, often with bilateral involvement. Unexplained lameness, particularly of the forelimbs could also constitute a possible case of neurofibroma. These suspicions would be strengthened if there is a previous history of neurofibromata on the property or if in fact nodular lesions were palpated along the peripheral nerves during clinical examination.
Work is proceeding to investigate the aetiology of this disease. There is a tendency for groups of cases to occur on particular farms and in geographic localities throughout New South Wales. It is imperative that, where possible, all cases of neurofibromata detected in cattle at slaughter are traced back to the property of origin using the tail-tag identification system
I am indeed grateful to the Veterinary Inspectors for their past co-operation in this matter and look forward to the same co-operation in the future.