Diferential Diagnosis between Esophageal Granuloma and Pulmonary Metastasis

Abstract

Background: Spirocercosis is a parasitic infection caused by Spirocerca lupi. This pathology affects canid carnivores, especially domestic dogs. Early diagnosis has been proven challenging and most infected animals are diagnosed when disease is in advanced stage. Exams such as computed tomography scans or radiographs can aid in disease confirmation.
Radiographic exam frequently reveals the presence of a mass located in mediastinal region, which can be erroneously diagnosed as pulmonary mass. The aim of this study was to report the differential diagnosis between paraesophageal granuloma, possibly due to spirocercosis, and pulmonary metastasis in a dog with a history of neurofibrosarcoma.
Case: A 8 year-old male Cocker Spaniel dog, weighing 17.4 kg, was presented with anterior limb suspension and a recurrent nodule of 2.0 cm diameter, located on the main pad, with previous diagnosis of neurofibrosarcoma (malignant Schwannoma). Routine evaluation work-up included thoracic radiographs and abdominal ultrasound for clinical staging, electrocardiogram, complete blood count (CBC), coagulogram, renal and hepatic function tests, with results within the normal range for the species. The dog submitted to left anterior limb amputation due to recurrent neurofibrosarcoma in the carpal region. Histopathological exam confirmed recurrent neurofibrosarcoma without vascular invasion. Considering neoplasm biological behavior and clean surgical margins, only routine follow-up was established, with clinical exams. The dogwas presented to the Veterinary Hospital five months after surgical treatment and it was presented with fever, prostration, and history of vomiting. Radiographic exam showed a circumscribed mass in caudal mediastinal area. Computed tomography scan was performed to best evaluate the mass and the result was compatible with paraesophageal abscess. These findings were consistent with paraesophageal abscess with necrotic center caused by Spirocerca lupi; however, it was not possible to exclude the possibility of lymph node neoplasms, with necrotic center/secondary abscess. Coproparasitological test result was negative; however, considering the endemic aspect of spirocercosis, the dog was treated with Ivermectin was given orally, for 14 days, and complete remission was observed at the end of the treatment, without any significant side effects.
Discussion: Spirocercosis has a worldwide dissemination, limited only by the presence of intermediate host. In endemic regions, prevalence in dogs may be 100%. Diagnosis may be challenging, especially in atypical cases and in patients with complications. Spirocercosis diagnosis may be achieved from therapeutic response in typical cases, with suggestive
radiographic and tomographic findings. Radiologic and tomographic findings in this case were similar to common spirocercosis findings. Follow up by a veterinary oncologist is of utmost importance; an unprepared veterinarian could indicate thoracotomy or even euthanasia. Even though coproparasitological exam was negative, the endemic aspect of spirocercosis in the area supported the decision for treatment and therapeutic diagnosis. Oncologic patients should be carefully evaluated,
for not all pathologies they develop after a neoplasm diagnosis are related to cancer. Knowledge of disease biologic behavior is essential to make correct decisions regarding patient health status.
Keywords: Spirocerca lupi, granulomas, neurofibrosarcoma.