Page 471 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 23 Cancer of the Gastrointestinal Tract 449

this is a marginal excision. However, the degree of tumor encap- Pathology and Behavior
sulation will help guide whether or not adjunctive RT is indi- It is postulated that with spirocercosis-associated sarcomas, a
cated. Regional LNs should be sampled for staging purposes.
VetBooks.ir salivary gland is generally straightforward. If the parotid salivary parasitic esophageal granuloma undergoes malignant transfor-
The surgical approach to the affected mandibular or parotid
mation leading to the development of an esophageal sarcoma,
gland is removed, care must be taken to identify and protect the typically in the caudal thoracic portion of the esophagus. 234
facial nerve. If this is not possible, facial nerve paralysis may occur. Histologic types of spirocercosis-associated sarcomas include
In rare cases of zygomatic salivary neoplasia, 214,215 the zygomatic OSAs, fibrosarcomas, and undifferentiated sarcomas. 239 Metas-
salivary gland is approached via an orbitotomy and removal of the tasis to the lungs was reported in 5 of 11 dogs at necropsy. 234
zygomatic arch. 214 Additional metastatic sites included kidneys, adrenals, stom-
ach, regional LNs, tongue, and the heart. 234 Complicating fac-
Prognosis tors include the presence of megaesophagus and hypertrophic
osteopathy. 234
In one retrospective study of dogs and cats with salivary gland Plasmocytoma, 240 adenomatous polyp, 241 leiomyosarcoma, 242
neoplasia, the median survival times were 550 days and 516 days carcinoma, 243 adenocarcinoma, 243 adenosquamous carcinoma, 244
for dogs and cats, respectively. 204 In that study, patients were and squamous cell carcinoma 245 have also been reported in dogs,
treated with surgery alone or in combination with RT or chemo- but these are rare. Squamous cell carcinoma is the most common
therapy. 204 The small number of patients treated with adjunctive esophageal tumor in cats, typically occurring in the middle third
therapy in that study makes it difficult to make a general recom- of the esophagus just caudal to the thoracic inlet. 246,247
mendation for adjunctive therapy. Postoperative RT is generally Leiomyomas are benign tumors of the muscularis of the esoph-
recommended, especially in cases where the tumor is invasive agus. They have been reported in the distal esophagus near the
and has extended beyond the capsule. 216 Recommendations for gastroesophageal junction in dogs. 238,248 In some cases, multiple
chemotherapy are less defined due to the paucity of information leiomyomas can occur in the distal esophagus and the stom-
in the literature, but may be indicated in cases with evidence ach. 232,233 Leiomyomas do not invade the esophageal mucosa. In
of metastatic disease and with highly malignant histopathology. contrast, low-grade leiomyosarcomas occasionally penetrate the
esophageal mucosa. 242
Comparative Aspects Paraesophageal tumors, such as thyroid, thymic, or heart base
tumors, can invade the esophagus. 249,250
Salivary gland adenocarcinoma has been reported in many other
mammalian species other than dogs and cats. 217–225 History and Clinical Signs
Treatment of salivary carcinoma in humans is commonly surgery
followed by RT. 226–229 Factors that have been associated with a neg- Clinical signs are usually related to obstruction of the esophagus,
ative prognosis in one study included male sex, perineural invasion, leading to regurgitation and weight loss. The presence of ulcer-
high risk pathology, and late stage. 226 Another study found that age, ation of the mass can cause melena and secondary anemia.
sex, stage, site, and skin or bone invasion were significantly associ- Respiratory signs can occur if aspiration pneumonia or meta-
ated with survival. 227 The use of postoperative RT has been shown static disease develops.
to improve locoregional control. 227 Local control has been shown Leiomyomas often are an incidental finding but can occasion-
to be significantly associated with tumor stage and treatment type, ally cause signs associated with esophageal obstruction. 232,233,243
with the combination of RT and surgery being superior to surgery
alone. 228 Tumor stage was significantly associated with survival. 228 Diagnostic Tests and Workup
Five- and 10-year survival rates are 68% 229 and 50%, respec-
tively. 227 A 20-year actuarial rate of local control of 57% was Diagnostic tests for esophageal masses usually include survey
reported in one study with a 12-year probability of distant metas- thoracic radiographs, contrast esophagram, esophagoscopy (Fig.
tasis of 40%. 227 23.12), and CT scan (Fig. 23.13). 242 Survey radiographs may show
retention of gas within the esophageal lumen, a mass, or esopha-
geal dilatation proximal to the mass (Fig. 23.14). Spondylitis on
SECTION C: ESOPHAGEAL TUMORS the ventral aspect of the vertebral body T6 to T12 was detected
radiographically in 12 of 15 dogs with spirocercosis-associated
esophageal sarcoma. 234 A positive-contrast esophagram may show
PIERRE M. AMSELLEM AND a stricture or mass lesion in the esophageal lumen. Ultrasound- or
JAMES P. FARESE CT-guided aspirates can be performed for cytologic evaluation.
Endoscopic biopsies of esophageal masses are possible; however,
Incidence and Risk Factors for smooth muscle tumors, such as leiomyomas and leiomyo-
sarcomas, they are usually unrewarding, as these tumors do not
Esophageal neoplasia is rare in dogs and cats. Esophageal sarcomas have penetrate the esophageal mucosa. 242,248 A surgical approach may
been reported in association with infestation by the nematode Spiro- be needed in these cases to obtain an incisional biopsy; however,
cerca lupi. 230–237 Although this parasite has been reported worldwide given the invasive nature of the surgical approach, most biopsies
(South Africa, Kenya, India, Israel, the southeastern United States), are excisional.
Spirocerca lupi–associated esophageal granulomas and sarcomas are A fecal flotation test may be performed in dogs with esophageal
reported mainly in Israel. 230–237 Leiomyomas may have a genetic masses to test for Spirocerca lupi eggs, particularly in areas where
component, as a high incidence was reported in a colony of laboratory the parasite is endemic. This is a poorly sensitive test; eggs were
238
beagle dogs. Most animals with esophageal tumors are middle-aged detected in only two of eight dogs in one study of spirocercosis-
or older and there does not seem to be a gender predisposition. associated sarcomas. 234