Papillary Renal Cell Carcinoma With Widespread Metastases in an Arabian Mare

Abstract

This report describes a case of massive renal cell carcinoma (RCC) causing mild chronic colic in a 20-day-postpartum Arabian mare. The mare presented with deteriorating abdominal pain following normal parturition. Clinical examination revealed tachycardia, tachypnoea, weak intestinal motility and pale mucosal membranes. Rectal examination identified a very large mass in the caudal part of the abdominal cavity, and abdominal ultrasound examination revealed a huge space-occupying mass with renal architecture. During midline exploratory laparotomy, a massive tumour was observed in the anatomical location of the left kidney, with numerous adhesions to abdominal organs. Due to the severity of the condition and intra-abdominal spread of the neoplasm, the horse was euthanized intraoperatively. Upon necropsy, a 23-kg mass was found in the left kidney, along with widespread metastases to the liver, diaphragm and lungs. Histopathological examination confirmed primary and metastatic papillary RCC. This case highlights that colic should be considered a potential symptom of neoplastic lesions within the abdomen.

Keywords: colic; horse; kidney; renal cell carcinoma.

FIGURE 1

Ultrasound image depicting a large, heterogeneous, hyperechoic mass with regions of mineralization and a cavitary anechoic cystic structure at the level of the left kidney, extending caudal to the 17th and 18th left thoracic ribs. The maximum size of the kidney visualized in this section is 12.9 × 17.4 cm.

FIGURE 2

Renal cell carcinoma. (a) Right kidney appearing normal. (b) Longitudinally incised left kidney with a renal mass weighing 23 kg. (c and d) Numerous sessile and pedunculated masses of varying sizes scattered throughout the peritoneum, most prominently on the liver (yellow arrow), diaphragm (blue arrow) and lungs (black arrow).

FIGURE 3

Microphotographs of the primary renal cell carcinoma, its pulmonary metastases and immunohistochemical examination. (a) Kidney. Renal cell carcinoma with both papillary (black asterisk) and tubular (blue asterisk) patterns. H&E. Bar = 200 µm. (b) Diaphragmatic metastatic mass. Papillary arrangement of the metastatic neoplastic cells mimicking those of the primary neoplasm. H&E. Bar = 100 µm. (c) Pulmonary metastatic mass. Metastatic neoplastic cells are depicted in the upper portion of the picture, while hyperaemic pulmonary parenchyma is evident in the lower aspect of the figure. H&E. Bar = 200 µm. (d) Pax‐8 strong nuclear immunoreactivity of the neoplastic cells. IHC. Bar = 20 µm.