Use of contrast-enhanced ultrasonography for the detection of a feline insulinoma

Abstract

Case summary: A 14-year-old cat was presented with a 2-week history of ataxia, seizure-like episodes, vomiting and weight loss. Serum biochemistry revealed severe hypoglycaemia, associated with low serum fructosamine and high insulin concentrations. On abdominal ultrasound, a focal hypoechoic well-defined mass in the left limb of the pancreas was identified and the presence of an additional smaller nodule was suspected. Contrast-enhanced ultrasonography (CEUS) confirmed the presence of both lesions and revealed a third, even smaller nodule. Partial pancreatectomy was performed. Histopathology and immunohistochemistry confirmed the presence of a multifocal insulinoma. Six months later, the cat presented with tenesmus and obstipation. A colorectal adenocarcinoma was diagnosed with histopathology after partial excision of a colorectal mass. The cat was euthanased a month later owing to recurrent episodes of severe obstipation.

Relevance and novel information: This is the first clinical description of the use of CEUS in the diagnosis of feline insulinoma. Furthermore, the available scientific literature on feline insulinoma was reviewed.

Keywords: CEUS; Feline insulinoma; contrast-enhanced ultrasonography; immunohistochemistry.

Figure 1

Focal hypoechoic well-defined mass in the left limb of the pancreas, measuring 16 × 23 mm and deforming the pancreatic margins, detected at abdominal ultrasound performed with a linear probe. Cranial is to the left of the image

Figure 2

Cytological examination of the pancreatic mass samples, obtained by ultrasound-guided fine-needle aspiration, revealing clusters of intact cells showing indistinct cytoplasmic borders and uniform round nuclei containing a prominent nucleolus (modified Romanowsky stain, × 1000)

Figure 3

Evaluation of the pancreatic parenchyma with contrast-enhanced ultrasonography. An ill-defined small nodule is identified by subtraction in the left limb of pancreas (arrow), (a) 10 and (b) 30 s after injection of Sonovue contrast agent. (c) A prominent marginal feeding vessel is detected 45 s after in the centre of the nodule, appearing as a linear highly contrast-enhancing structure

Figure 4

Histopathological evaluation of the pancreatic parenchyma harbouring the larger nodule. (a) Islet cell tumour (carcinoma) composed of round uniform cells with round uniform nuclei (haematoxylin and eosin staining, × 1000). (b) Immunohistochemical staining with human antibody against insulin, showing normal pancreatic parenchyma with the presence of Langerhans islets (positive control; arrows) and a strong and homogeneous insulin staining of neoplastic cells in the right side of the image (× 400)