Neoplastic conditions of the esophagus

Ann E. Hohenhaus

Introduction

Esophageal tumors represent less than 0.5% of all canine tu­mors.¹ Both dogs and cats can develop esophageal tumors, which are typically malignant in both species.

Table 3.1: Clinical signs attributed to esophageal neoplasia in the dog

Histopathology

Many histological types of primary esophageal tumors have been described, including squamous cell carcinoma, adeno­squamous carcinoma, adenocarcinoma of the esophageal glands, neuroendocrine carcinoma, plasma cell tumor, and osteosarcoma.^1-11 Benign esophageal tumors such as leiomy­oma have been reported in the dog.^12-13 Secondary esopha­geal tumors originate from locally invasive tumors such as thyroid carcinoma or gastric carcinoma, or via distant metas- tasis.^1,14 In one study, tumors metastatic to the esophagus were three times more common than primary esophageal tumors (Figure 3.16).¹

Clinical signs

The clinical signs of esophageal tumors in the dog and cat have been summarized in Table 3.1. Most of the clinical signs as­sociated with esophageal neoplasia can be explained by ob­struction of the esophageal lumen by tumor or because of pain during swallowing. An association has been made between chronic upper respiratory signs and papillomatous esophagitis in a cat.¹⁵ This cat was believed to have had chronic reflux into the pharynx and nasal passages resulting in the chronic upper respiratory signs.

Diagnosis

Physical examination findings and routine blood tests are not typically contributory to the diagnosis of esophageal neoplasia unless a cervical mass is present. Diagnostic imaging is re­quired to localize the esophageal tumor and determine the best approach for biopsy and treatment.¹⁴

Figure 3.15:

Esophageal tumor in a cat. This contrast esophagram demonstrates a filling defect secondary to an esophageal tumor in a cat.

Plain radiographs are of limited utility in the diagnosis of esophageal neoplasia unless a soft tissue mass associated with the esophagus is seen. Thus, the value of plain radiographs is in eliminating other esophageal disorders, such as foreign bodies and megaesophagus. As a sequela of vomiting and regurgita­tion, air may be present in the esophagus. Also, pulmonary infiltrates consistent with aspiration pneumonia may be seen. A contrast esophagram will frequently show esophageal dila­tion proximal to a tumor, a filling defect in the area of the tumor, or leakage of contrast material from an esophageal de­fect caused by the tumor (Figure 3.15). When interpreting contrast esophagrams, it is important to remember that the

Figure 3.16:

Appearance of striated muscle in a cat esophagus. This Figure shows a metastatic renal sarcoma in the esophagus (arrows) of a cat. Note the normal striated muscle of the distal feline esophagus on the right.

Figure 3.17:

Esophageal squamous cell carcinoma in a dog. This Figure shows an endoscopic view of a squamous cell carcinoma in the esophagus of a dog.

distal portion of the feline esophagus consists of striated mus­cle and will normally have a regular herringbone appearance (Figure 3.16). Fluoroscopic evaluation of the esophagus is not always necessary for a diagnosis of an esophageal tumor unless an evaluation of esophageal motility is required.

Esophageal tumors are typically intraluminal. Esophagoscopy allows a biopsy to be taken from the luminal surface and is a less invasive procedure than thoracotomy (Figure 3.17). Con­sequently, esophagoscopy is typically the procedure of choice to obtain a sample for histopathological evaluation of an esophageal tumor. Multiple tissue samples should be obtained with the biopsy forceps to ensure adequate tissue for histo­logical evaluation.

Treatment

Although surgical resection of esophageal tumors has been the treatment modality of choice, rarely is an esophageal tumor amenable to complete resection because the esophagus is in­capable of longitudinal stretching and heals poorly under ten­sion. Reconstruction of the esophagus has been attempted by microvascular colon transfer and also by use of a vascular skel­etal muscle graft.^16-17 Currently, neither procedure is being widely used.

Only single case reports of other treatment modalities, such as chemotherapy, radiation therapy, and photodynamic therapy for esophageal tumors have been reported. Except for lym­phoma, chemotherapy is unlikely to be of benefit in the treat­ment of esophageal neoplasia. The utility of radiation therapy for the treatment of esophageal tumors is limited by the poor tolerance of normal structures in the thoracic cavity for radia­tion-induced side effects. Photodynamic therapy, utilizing a photosensitizing dye activated by a laser light source, was ad­ministered to a dog with esophageal squamous cell carci- noma.¹⁸ The tumor underwent a partial remission and the dog survived for 9 months before recurrent regurgitation and as­piration pneumonia resulted in euthanasia.

Supportive care

Oral alimentation is compromised by esophageal tumors and a gastrotomy tube should be placed to provide adequate nutri­tion and decrease the risk of aspiration pneumonia from re­gurgitation. Naso-esophageal or esophagotomy tubes are not appropriate in patients with esophageal tumors.

Systemic complications of esophageal neoplasia

Paraneoplastic syndromes are sequela of cancer occurring re­mote from the site of the primary tumor.

Passive congestion of the liver causing ascites and hindlimb edema has been attributed to caudal vena cava compression by an esophageal leiomyoma ofthe caudal esophagus.²⁰Two other complications of esophageal tumors reported include tracheal invasion and aspiration pneumonia. ^1,6

Survival

Typically, esophageal tumors are too advanced at the time of diagnosis to allow successful treatment. Most cases have a re­ported survival of less than 1 month. An exception is a single reported case of esophageal plasma cell tumor treated with surgery with a survival in excess of 18 months.⁵

O Key Facts

■ Esophageal tumors are rare in both dogs and cats.

■ Tumors metastatic to the esophagus are more common than primary esophageal tumors.

■ Spirocerca lupi is a known cause of esophageal tumors in dogs.

■ Clinical signs are most frequently related to esophageal obstruction.

■ Resection of the esophageal tumor is rarely possible because the tumor is advanced at the time of diagnosis, leading to short survival times.