What is esophageal cancer? How does it differ from throat cancer?

Esophageal CancerThe occurrence of esophageal cancer in dogs is very rare. It accounts for even less than 0.5% (1 in 2,000) of all canine cancers. The occurrence of esophageal cancer has no sex or breed predilection, however, it’s rarely seen in younger dogs and almost always found in dogs that are aged seven and above.


What types of canine esophageal cancer are there?

The most 5 commonly reported primary esophageal tumors in dogs include:

  • Sarcomas: fibrosarcoma and osteosarcoma occurring in the mesenchymal cells (the body’s connective tissue).
  • Carcinomas: squamous cell carcinoma forms in the epithelial cells (lining of the body’s organs and outer surfaces).
  • Leiomyosarcoma: Also known as LMS, a malignant tumor that grows in smooth muscle fibers of the body (cells within an organ that are hollow).
  • Leiomyomas: The benign form of leiomyosarcoma, occurs in the deep muscle fibers and smooth muscle fibers.
  • Plasmacytoma: A benign tumor that grows with the plasma cells in your dog (bony or soft tissue).

Sadly, metastatic lesions are thrice more common than primary ones. They are usually paraesophageal (besides the esophagus) tumors of the thymus (a lymphoid organ located in the superior mediastinum and lower part of the neck and is necessary for the development of immunological function), heart base, thyroid as well as mammary adenocarcinoma and lymphoma.

Throat and esophageal cancer are very similar in that they occur in the same types of cells in parts of the body right next to one another. The primary distinction between them is that esophageal cancer occurs in the digestive tract below the throat and larynx but above the stomach.


Leiomyosarcomas Vs. Leiomyomas Esophageal Tumors

The core difference between leiomyosarcomas and leiomyomas is that leiomyosarcomas are malignant and pose a much greater health risk. Fortunately, though leiomyomas can become leiomyosarcomas, they can remain benign and are far more common than leiomyosarcoma. Leiomyomas are benign tumors that develop from smooth muscles in the gastrointestinal tract. Unlike leiomyosarcomas, most of them develop from the muscularis propria (deep muscular layer), with a smaller percentage growing from the muscularis mucosae (thin layer of smooth muscle).

Esophageal leiomyomas are solitary, slow-growing tumors, although multiple tumors can occur. In dogs, leiomyomas are most commonly found in the stomach at the gastroesophageal junction (the junction between the stomach and the esophagus). In contrast, leiomyosarcomas can spread faster and are more likely to metastasize.

Leiomyosarcoma and leiomyomas are unusual tumors arising from various sites like the genitourinary tract, gastrointestinal tract, peritoneum, soft tissues, blood vessels, lungs, liver et al. It contributes 1-2% to all malignancies affecting the gastrointestinal tract and is rarely found in the esophagus.


Histology Of Leiomyomas

Histologically, leiomyomas are different from leiomyosarcomas with respect to a lower number of mitotic figures (cell division) as well as the absence of necrosis (premature death of cells and living tissues). Low-grade leiomyosarcomas may behave similarly to leiomyomas in dogs after marginal excision (removal of the entire lesion and only a small margin of surrounding tissue).

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Spirocera Lupi Parasites & Hypertrophic Osteopathy

Spirocerca lupi is a parasite that is one of the primary esophageal nodules causes that eventually form esophageal cancer and has the secondary effect of that cancer commonly spreading to the larger bones of your dog’s body, known as hypertrophic osteopathy. This parasite is classified as a nematode and is typically found in tropical and subtropical regions. Nodular masses and granulomas are formed in the dog’s esophagus and start benight but can undergo a neoplastic transformation to become osteosarcoma or fibrosarcomas.


What are the symptoms of esophageal cancer?

Most symptoms of esophageal cancer can be symptoms of other cancers or conditions with the notable exceptions being pain when swallowing and heart issues. That said, if you notice any of these symptoms you should take your dog to the vet for further diagnosis:

  • Muscle atrophy: The weakening of muscles with few activity or diet changes.
  • Debilitation: Exhibiting lameness or loss of motor functions
  • Weight loss: Body mass changes over around 10% could indicate an underlying issue.
  • Dysphagia: Not wanting to eat and having pain in swallowing or keeping food down.
  • Mitral regurgitation: Reverse circulation of blood in the heart due to defective functioning of the valves.
  • Pneumonia: Fluid build up in the lungs impacting aspiration (secondary effect of the cancer).

These symptoms can occur as leiomyosarcoma cells grow into nodules on your dog’s esophagus. Regular visits to the vet and taking your dog in for examination if they show unusual behavior or health is always the best way to diagnose cancers early.


How is esophageal cancer diagnosed by veterinarians?

There is a battery of tests that may make sense for your veterinarian to use in diagnosing esophageal cancer.

  • Radiographs: A form of x-rays.
  • Positive-contrast esophagogram: A different form of x-rays that better shows tumors or growths.
  • Esophagoscopy: Using a camera to look at the esophagus for signs of cancer.
  • Biopsies: Analysis of tumors taken from the esophagus (if possible).
  • CT or MRI scans: Similar to x-rays but provide even greater detail of the esophagus.

Veterinarians usually go for plain radiographs as the first indicator of an issue in the dog’s esophagus. Due to complete or partial upper-gastrointestinal obstruction, radiographs may reveal retention of gas within the esophageal lumen (a cavity or channel within a tube or tubular organ), a mass or esophageal dilatation (it is the technique used to stretch or open the blocked portion of the esophagus) close to the cancer.

A positive-contrast esophagogram (radiograph of the esophagus) with or without the fluoroscopy will reveal a stricture or mass lesion in the lumen. If x-rays are inconclusive an esophagoscopy may be needed. This allows the vet to get a clear picture of the tumor which is usually ulcerated by using a camera down the dog’s throat.

Biopsies reveal necrosis (premature death of cells) and inflammation. Unfortunately, biopsies of leiomyomas yield minimal results since they are movable, circumscribed submucosal masses. Sometimes advanced CT or MRI may be helpful to determine the extent of the disease. Open surgical biopsy via thoracotomy (incision made into the chest to gain access to the thoracic organs), or cervical exploration is another way of collecting tissue for diagnosis.


How is esophageal cancer treated in dogs?

The metastatic nature of the disease makes many therapeutic options non-viable. Intrathoracic surgeries have been attempted but have not yielded positive results. For tumors located in the caudal esophagus or cardia (opening of the esophagus into the stomach), gastric advancement through the diaphragm can be attempted.

There are different procedures to partially replace the resected esophagus like microvascular transfer of colon or small bowel. However, theories substantiating their efficacy as potential options for treatment remain inadequate.

Chemotherapy has not been attempted properly. Radiation is sometimes used to treat cervical esophageal cancer, but for treating intrathoracic esophageal cancer, it cannot be used because of the intolerance of surrounding normal tissues like the lung and heart.

Short-term relief can be achieved through esophagotomy (making an incision into the esophagus to remove any foreign substance that obstructs the passage) or gastrostomy (construction of a permanent opening from the external surface of the abdominal wall into the stomach for inserting a feeding tube). Thoracotomy or celiotomy (incision of the abdomen) may be attempted in case of benign leiomyomas of the esophagus or the cardia.


What’s the prognosis for canine esophageal cancer?

Sadly, neoplasms of the esophagus are among the most lethal neoplasms your dog can be diagnosed with. Because of its difficult location to access and the esophagus acting as a connection between your dog eating nutrients and ultimately processing them to maintain normal metabolic functions, esophageal cancer is hard to treat if it’s malignant or has metastasized. A resection (removal) of the impacted esophagus is not possible and various other typical cancer treatments may not be good options either, so unless the tumors are non-malignant, the prognosis for advanced esophageal cancer is very grim.

Thank you for utilizing our Canine Cancer Library. Please help us keep this ever-evolving resource as current and informative as possible with a donation.


Withrow and MacEwen’s Small Animal Clinical Oncology– Stephen J. Withrow, DVM, DACVIM (Oncology), Director, Animal Cancer Center Stuart Chair In Oncology, University Distinguished Professor, Colorado State University Fort Collins, Colorado; Research, School of Veterinary Medicine University of Wisconsin-Madison Madison, Wisconsin David M. Vail, DVM, DACVIM (Oncology), Professor of Oncology, Director of Clinical

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