Neoplasm

Neoplasm Part 2 is to be read in conjunction with Neoplasm Part 1.

Meat inspectors may encounter various neoplasms for which they must determine a disposition. As discussed in Neoplasms Part 1, a key consideration is distinguishing whether a neoplasm has systemically spread or is localised. This often relates to a tumour being malignant (metastasis) or benign respectively, but without microscopic diagnosis, this cannot be confirmed.

In export abattoirs if an inspector suspects a neoplasm, they are to retain the carcase and its parts and inform the on-plant veterinarian who will perform a detailed inspection and determine their disposition.

In non-export abattoirs the inspector is responsible for performing a detailed inspection and determine their disposition.

The following are examples of benign and malignant neoplasms in food animals.

Benign Neoplasms

Neurofibroma

A neurofibroma is a benign (non-cancerous) tumour that grows on nerve tissue. Neurofibroma in cattle particularly in older females can occur in various locations. They are often found in the brachial plexus (network of nerves that originates from the spinal cord and branches out to the nerves that supply the muscles and skin of the forelimb), heart (Photo 1), and intercostal nerves (Photo 2).

Neurofibroma lesions can be trimmed and condemned together with an adequate margin of healthy tissue. The remainder of the carcase and its parts can be judged on their merits.

Renal adenomas

Renal adenomas are benign tumours arising from the kidney's tubular epithelium appearing as well-defined masses in the cortex (Photo 3). Note the smooth, regular, and well-defined border between normal issue and the tumour.

Kidneys are to be condemned, and the carcase and its parts judged on their merits.

Lipoma

    Lipomas are generally benign, slow-growing tumours composed of adipose tissue (fat cells). They can occur in various locations but are often found subcutaneously (under the skin) in the neck, head, and shoulder regions (Photo 4). Lipomas are generally not malignant however, there are rare cases of infiltrative lipomas, which can behave aggressively by invading surrounding tissues.

Lipoma tumours can be trimmed and condemned together with an adequate margin of healthy tissue. The remainder of the carcase and its parts can be judged on their merits.

This tumour is fully circumscribed; it has a good blood supply and there is no evidence of secondary tumours.

Note: benign tumours rarely metastasise.

Condemn the organ (heart) and judge the carcase and its parts on their merits.

Malignant Tumour

Bovine ocular squamous cell carcinoma (eye cancer)

Eye cancer occurs in older cattle, particularly in Herefords and Friesians with unpigmented eyelids and eyeballs. Ultraviolet (UV) radiation is thought to predispose cattle to cancer eye.

At ante-mortem inspection, animals with epitheliomas only affecting the eye (see photo 6) are to be categorised as a “suspect animal”. If at post- mortem inspection, the tumour has not invaded the osseous tissue, the parotid lymph node is not enlarged and no other tumours are found, the head is to be condemned, and the carcase and remaining parts judged on their merits.

Animals presenting with ocular epitheliomas that have invaded the osseous structures of the head are classified as "not fit to load" and should not be transported to the slaughter facilities. If an animal exhibiting epitheliomas like those illustrated in Photo 7 arrives at a slaughter premise, this occurrence should be reported as an animal welfare incident and is reported to the state/territory jurisdiction in accordance with described procedures. On animal welfare grounds, such animals should be processed immediately as " emergency slaughter animal” (also known as an “emergency kill”).

Should post-mortem inspection reveal no additional tumours, the affected head must be condemned, while the carcase and remaining parts judged on their merits. However, if significant tumour spread around the eye (observed after skin removal) is detected, or metastasis to lymph nodes of the head region (including parotid [Photo 8], retropharyngeal, or Atlantal lymph nodes), both the carcase and associated parts must be condemned. The lungs should also be examined for evidence of metastasis (Photo 9).

Research (ref. 1) indicated that 11% of cows with invasive carcinoma of the eye or eyelids exhibited metastases. Additionally, a study (ref. 2) found that 61% of animals with an enlarged parotid lymph node had regional lymph node metastases, and among these, 28% also demonstrated lung metastases.

1.Hamir AN, Parry OB. An abattoir study of bovine neoplasms with particular reference to ocular squamous cell carcinoma in Canada. Vet Rec 1980;106:551–3

2. Klein WR, Bier J, Van Dieten JS, et al. Radical surgery of bovine ocular squamous cell carcinoma (cancer eye) complications and results. Vet Surg 1984; 13:236–42.

Lymphosarcoma

Lymphosarcoma also known as lymphoma) are cancers that affect lymphocytes which are a type of white blood cell that plays a crucial role in the immune system.

Lymphosarcoma is a malignant tumour affecting lymphoid tissue including lymph nodes and other tissues like the spleen and bone marrow.

Thymic and multicentric lymphoma represent distinct forms of lymphosarcoma in animals, differing primarily in their primary location and subsequent spread patterns. Multicentric lymphoma involves multiple lymph nodes and organs throughout the body, while thymic lymphoma originates in the thymus gland in the chest cavity.

Lymphosarcoma in cattle may arise spontaneously (referred to as "sporadic") or result from infection with bovine leukemia virus (BLV), also called bovine leukosis virus; the latter is often referred to as an enzootic bovine leukosis. Sporadic lymphosarcoma in cattle is unrelated to infection with BLV. Bovine leukemia virus is classified as a retrovirus, meaning it integrates its genetic material into the host cell and uses the host cell machinery to replicate itself.

Sporadic lymphosarcoma is typically observed in younger animals, while enzootic leukemia predominantly affects older animals (4+ years).

Clinical signs associated with development of lymphosarcoma are highly variable, because the affected organ(s) will dictate the predominant clinical signs. Tumours may appear as yellow-tan, discrete nodular masses or a diffuse tissue infiltrate.

The disposition is carcase and carcase parts are to be condemned.

Intestinal adenocarcinoma

Intestinal adenocarcinoma is a common malignant tumour of the small intestine, in older sheep (Photos 15, 16 & 17)

 Intestinal adenocarcinoma can spread to the mesentery, regional lymph nodes, and even the peritoneum (abdominal lining). In rare cases, metastasis to the liver and lungs can occur.  

 The disposition is carcase and carcase parts are to be condemned.   

Adrenal carcinoma

Adrenal carcinomas are the most common tumour found in cattle. They are malignant and often invade the vena cava and metastasise to the lungs and liver (Photo 20).

The carcase and its parts are to be condemned.

The liver, lungs, and kidneys are filter organs composed of small blood vessels. When tumour cells break away from the primary tumour they regularly end up in these organs which has likely occurred in these cases. Livers, lungs and kidneys should always be inspected when determining if a neoplasm is benign or malignant.

Disposition.

In an export plant retain carcase and all parts for the OPV.

Domestic or tier one plants with no OPV

Photo 21 is malignant neoplasms, and it is likely that more tumours would be found in others organ in particular the lungs and kidneys (filter organs) so would be judged by the section of schedule 3 which states;

Multiple tumours (evidence of metastasis or multiple lesions in different organs) carcase and all parts condemned.

If no further tumours are found condemn the liver and judge carcase on merits.