Transendoscopic laser ablation of an esophageal plasma cell tumor in a cat

Introduction

Esophageal neoplasms in both dogs and cats are rare and account for less than 0.5% of all cancers.^1,2 Clinical signs associated with esophageal tumors are often non-specific and include regurgitation, weight loss, dysphagia, ptyalism, anorexia and signs associated with aspiration pneumonia.^{1 –6} Squamous cell carcinoma (SCC) represents the most diagnosed malignant esophageal neoplasm in cats and most commonly occurs in the cranial thoracic esophagus. ⁶ Sarcomas (osteosarcoma and fibrosarcoma) may develop in dogs secondary to infestation with the nematode Spirocerca lupi.^{7 –9} Treatment of esophageal neoplasms has historically involved chemotherapy, surgical resection and radiation therapy. The prognosis for primary esophageal neoplasms is generally considered poor owing to difficult surgical resection, associated surgical complications and late-stage diagnosis. ³ Transendoscopic laser ablation is an emerging minimally invasive technique that has been successfully used in dogs with S lupi-induced esophageal sarcomas as an alternative to open-chest surgery.^{8 –10} This technique is associated with a comparable long-term survival period, lower cost and shorter hospitalization time compared with open-chest surgery in dogs with S lupi-induced sarcomas.^8,10 To date, this technique has never been reported on cats or patients with esophageal round cell tumors. The primary aim of this report was to increase awareness of feline esophageal neoplasms and describe a minimally invasive treatment or palliative care method to address these tumors.

Case description

A 15-year-old male castrated domestic shorthair cat weighing 3.8 kg was presented to the emergency service for evaluation of a 2-day history of hyporexia, lethargy and reported vomiting. The cat’s medical history was otherwise unremarkable. On presentation, the cat was underconditioned, with a body condition score of 3/9, had a right-sided thyroid slip and a grade II/VI systolic cardiac murmur.

Abdominal and thoracic radiographs revealed a suspected caudal thoracic/esophageal soft tissue opacity, raising concern for an esophageal foreign body or neoplasia (Figure 1). Complete blood count and serum biochemistry were performed and unremarkable. The cat was anesthetized and endoscopy was performed. A large mass with irregular tissue and increased friability was identified within the middle third of the esophagus, causing approximately 80% occlusion of the esophageal lumen. The tissue surrounding the mass was hyperemic and edematous (Figure 2). Endoscopic pinch biopsies of the mass were collected and submitted for histopathologic evaluation.

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Figure 1

Right lateral view showing a caudal thoracic/esophageal soft tissue opacity

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Figure 2

Endoscopic image showing a large, irregular esophageal mass

After esophagoscopy, a CT scan of the thorax and abdomen was performed to evaluate the extent of the mass and assess for metastatic disease. Within the caudal intrathoracic esophagus, a large (length × height × width = 2.3 × 2.3 × 2.0 cm) mural mass lesion was identified (Figure 3). Adjacent to the esophageal lesion, a small (length × height × width = 11 × 7.2 × 7.9 mm), poorly defined, heterogeneously contrast-enhancing nodule dorsal to the pulmonary artery was identified, raising concern for pulmonary metastasis. Prednisolone (1.1 mg/kg PO q24h), maropitant citrate (1 mg/kg PO q24h) and mirtazapine (2 mg/cat transdermally as required) were administered pending results of the histopathologic examination.

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Figure 3

CT image showing a large mural mass lesion

Histopathology revealed a proliferation of spindyloid to round cells, most consistent with a sarcoma, with histiocytic sarcoma, osteosarcoma and rhabdomyosarcoma all considered. A lymphoma or plasma cell neoplasia was considered less likely. The cat returned 2 weeks later for palliative debulking of the mass using endoscopic-guided laser ablation. After routine induction of anesthesia, the patient was placed in left lateral recumbency and an 18 Fr Foley catheter was passed into the esophagus and inflated with 10 ml of water to occlude the distal esophagus under esophagoscopic visualization and guidance. A 7 mm flexible video-endoscope was used for the procedure. A 400 µm Diode laser was then utilized at 3.5 W to transect the mass along the base. The mass was manipulated via endoscopy and raptor graspers were utilized adjacent to the scope to aid in visualization. The mass was then removed using a raptor grasper without complication. Approximately 80% of the mass was debulked, which resulted in clear visualization of the lower esophagus (Figure 4a). A 19 Fr esophagostomy tube was then routinely placed, which spanned the length of the affected tissue and terminated in the distal esophagus, after resection of the mass to allow administration of food and medications and possibly help maintain patency of the esophageal lumen in the event of tumor regrowth. The total procedure time was 66 mins. The patient was discharged the same day with prednisolone (1.1 mg/kg PO q24h), maropitant citrate (1 mg/kg PO q24h), mirtazapine (2 mg/cat transdermally as required), sucralfate (0.3 g PO q8h), omeprazole (1 mg/kg PO q12h) and instructions for an enteral feeding plan.

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Figure 4

Endoscopic images of the esophagus (a) immediately postoperatively and (b) 2 weeks after laser ablation showing no gross evidence of regrowth with an esophagostomy tube (top left corner) in place

Histopathologic examination of the debulked mass was inconclusive and revealed a poorly differentiated malignant neoplasm. Pathologists were unable to determine the cell of origin but suspected a carcinoma or a round cell tumor (specifically lymphoma) given the cell morphology. Immunohistochemistry (IHC) staining was performed for pancytokeratin (epithelial marker), CD3 (T-cell marker) and Pax5 (B-cell marker). The neoplastic cells did not show immunolabeling for pancytokeratin, CD3 or Pax5. CD18 staining was added to further rule out a round cell tumor. Approximately 90% of the neoplastic cells were positively labeled for CD18, which supported the diagnosis of a round cell tumor. Based on the negative CD3 and PAX5 labeling, a plasma cell tumor was considered the most likely diagnosis; however, a histiocytic sarcoma could not be entirely ruled out. MUM1 and CD204 staining were added to rule out a plasma cell tumor and histiocytic sarcoma, respectively. IHC confirmed the presence of a plasma cell tumor.

Two weeks after partial laser ablation of the mass, the cat was doing very well clinically, with no evidence of tumor regrowth on esophagoscopy (Figure 4b). However, given that incomplete margins were achieved using laser ablation, local recurrence is likely. Chemotherapy was initiated to slow tumor regrowth.

Six weeks after the initial procedure, the cat was re-evaluated by the medical oncology service as a result of persistent hyporexia. A repeat esophagoscopy and CT scan were performed owing to concern for tumor regrowth. There was no gross evidence of regrowth on esophagoscopy, though the mucosa appeared pale and irregular, with scant hemorrhage present. On examination, the cat was noted to have bilaterally enlarged prescapular and mandibular lymph nodes. Fine-needle aspiration of the right prescapular lymph node was performed and submitted to a clinical pathologist. The results were consistent with a histiocytic proliferation, with the cells exhibiting mild criteria of malignancy. The cytologic findings were most consistent with metastatic histiocytic neoplasia given the IHC staining pattern of the esophageal tumor. The CT scan revealed multifocal metastatic lymphadenopathy of the head, neck and thorax, as well as multifocal pulmonary metastasis. The esophageal mass was still present, though decreased in size compared with previous imaging. Systemic chemotherapy was initiated at that time.

After the first dose of chemotherapy, the cat’s appetite improved significantly. One week after initiating chemotherapy, the cat developed an anemia requiring a blood transfusion but was still doing well clinically. When the cat returned for its next dose of chemotherapy, it had gained weight. It was eating on its own, but the E-tube remained in place. A recheck examination 2 weeks later revealed weight loss. Its appetite and energy level had decreased significantly. The cat returned a few days later for humane euthanasia because of a decline in quality of life. Neither repeat esophagoscopy nor necropsy was performed at the time of death.

Discussion

Esophageal tumors in both dogs and cats are rare; therefore, information regarding the diagnosis, treatment and prognosis of esophageal tumors is limited. Diagnosis of esophageal neoplasia requires a multimodal approach, including thoracic radiography, endoscopy, CT and biopsy.^2,3,6 Survey radiographs may identify a soft tissue opacity within the mediastinum or gas distension of the esophagus proximal to the tumor. Radiographic findings may also include aspiration pneumonia and pulmonary metastasis. ¹¹ Esophagoscopy or CT is required to make a diagnosis of an esophageal mass and determine the extent of the lesion consistent with this case. Esophagoscopy allows direct visualization of the mass, as well as sample collection for cytology, histopathology and culture.

Surgical resection is considered the treatment of choice for esophageal neoplasms; however, esophageal surgery can have a high complication rate. Esophageal resection and anastomosis have reported postoperative complications, including respiratory complications, persistent regurgitation, dehiscence, tissue necrosis and stricture formation.^1,6,12 Surgery is generally only considered an option if less than 3–5 cm of the esophagus is affected owing to an increased risk of dehiscence when more than 5 cm of the esophagus is affected.^1,6 Radiation therapy can also be considered.

Most esophageal tumors in both dogs and cats are diagnosed late in the stage of the disease and are extensive at the time of diagnosis. Metastasis is present in more than 50% of dogs at the time of diagnosis. ⁶ In this case, a large portion of the caudal intrathoracic esophagus was affected, there was concern for pulmonary metastasis and the patient was clinically significantly impacted. Given these limitations and risks, surgery and radiation therapy were not pursued. Therefore, endoscopic-guided laser ablation of the esophageal mass was elected to cytoreduce the mass and provide the patient with immediate palliation. The patient was discharged later the same day. The median hospitalization time for dogs undergoing this procedure was 0 days in one study, compared with 6–9 days in dogs undergoing surgery.^9,10 Because complete resection was not possible, this procedure was followed by chemotherapy to prevent regrowth. No intraoperative complications occurred; however, hemorrhage from the tumor and esophageal perforation were acknowledged as major risks. The use of a Foley catheter was designed to promote visualization and achieve distension of the esophagus to prevent thermal injury to the surrounding healthy tissue. The placement of an esophagostomy tube was performed with the goal of ensuring ongoing nutrition as well as attempting to maintain patency of the esophagus in the event of tumor regrowth.

The cat in this report improved with transendoscopic laser ablation and survived for 76 days after the procedure, which suggests that the short-term prognosis for transendoscopic laser ablation is favorable. The long-term prognosis was ultimately poor, likely due to the presence of metastatic disease at the time of diagnosis. No recurrent clinical signs associated with the initial esophageal disease were present at the time of euthanasia. One study reported comparable long-term survival to esophageal surgery in dogs with S lupi-induced esophageal sarcomas; ¹⁰ however, no patients in that study had evidence of pulmonary metastasis.

Conclusions

Based on the results of this approach, transendoscopic laser ablation of esophageal tumors in cats should be considered a palliative treatment alternative to surgery. The procedure is relatively quick, with fewer associated complications compared with surgery and no need for prolonged hospitalization and/or pain medications. Additional studies are needed to corroborate the results of this approach.