Clinical differentiation between dogs with benign and malignant spirocercosis

Spirocerca lupi is a nematode infesting the canine oesophagus, where it induces the formation of a nodule that may transform into a malignant sarcoma. The current, retrospective study compared the clinical presentation, haematology, serum albumin and globulin and radiology of benign cases (n = 31) and malignant cases (n = 31) of spirocercosis.Dogs with spirocercosis-induced sarcoma were significantly older (6.4 ± 1.91 years) than benign cases (4.93 ± 2.87). In the malignant cases there were significantly (p = 0.03) more sterilized females (10/31) and fewer intact males (4/31) compared to 2/31 and 13/31, respectively, in the benign cases. Hypertrophic osteopathy was observed in 38.7% of malignant cases and in none of the benign cases (p = 0.0002). Common clinical signs included weight loss, regurgitation, anorexia, pyrexia (T ≥ 39.5°), respiratory complications and salivation but did not differ in prevalence between groups. On haematology, the malignant group had significantly (p < 0.05) lower haematocrit (0.34 ± 0.08 vs. 0.41 ± 0.07) and higher white cell count (31.6 ± 27.83 vs. 17.71 ± 13.18 × 103 μl−1), mature neutrophil count (26.06 ± 26.08 vs. 12.23 ± 9.96 × 103 μl−1) and thrombocyte count (493.15 ± 151.61 vs. 313.27 ± 128.54 × 109 μl−1). There were no differences in the mean corpuscular volume and immature neutrophil count. On radiology, the mass length was not significantly different, but the height and the width of the malignant masses were significantly larger (62.59 ± 15.15 mm and 73.93 ± 20.94 mm) compared to the benign group (46.43 ± 23.62 and 49.29 ± 25.56, respectively). Spondylitis was more prevalent in the malignant group (67.86% vs. 38.46%, p = 0.03). Examining secondary pulmonary changes revealed significantly higher prevalence of bronchial displacement in the malignant group (52% vs. 17%, p = 0.008).Hypertrophic osteopathy appeared to be a very specific but relatively rare (poor sensitivity) marker of malignancy. Female gender, anaemia, leukocytosis, thrombocytosis, spondylitis and bronchial displacement are significantly more common in malignant cases, but appear in benign cases as well. However, if found together in a specific case, they should increase the index of suspicion for malignancy in a diagnosed spirocercosis case.