Background

Primary hepatic neuroendocrine carcinoma (PHNEC) is an uncommon canine hepatobiliary tumour, comprising roughly 2%–14% of primary liver neoplasms. Clinical signs are nonspecific, and diagnosis requires histopathology with immunohistochemistry. Imaging modalities, such as abdominal ultrasonography and contrast-enhanced CT, assist in evaluating tumour characteristics, including haemodynamics and internal changes such as necrosis or haemorrhage. Few studies have reported CT features of PHNEC in dogs, and reports have lacked explanation for imaging findings. The aim of this case report was to describe specific CT features associated with PHNEC in a young French Bulldog.

Methods

A 4-year-old female-spayed French Bulldog presenting with anorexia, lethargy, and vomiting underwent clinical examination, laboratory evaluation, abdominal ultrasound, single-phase contrast-enhanced CT, laparoscopic liver biopsy, histopathology, and immunohistochemistry. Ultrasound identified multifocal coalescing hepatic nodules with hyperechoic centres and hypoechoic rims. CT scanning was performed under general anaesthesia, using a post-contrast acquisition after manual iohexol administration. Regions of interest were measured for Hounsfield unit quantification. Laparoscopic biopsy samples were obtained for cytology, histopathology, and IHC staining using AE1/AE3, chromogranin A, and synaptophysin.

Results

Ultrasound revealed widespread multifocal coalescing hepatic nodules with irregular margins. CT showed isoattenuating liver parenchyma with poorly defined hypoattenuating areas pre-contrast and heterogeneous post-contrast enhancement, including hypoattenuating, mildly enhancing coalescing masses distributed throughout the liver. Some nonenhancing areas suggested necrosis or haemorrhage; fat stranding and a cranial mesenteric vein filling defect were also present. Cytology suggested an epithelial tumour of intermediate malignancy. Histopathology confirmed a neoplastic epithelial cell population arranged in islands, tubules, and rosettes, with necrosis and haemorrhage. IHC demonstrated positive AE1/AE3 and chromogranin A staining, confirming PHNEC. Synaptophysin was negative. The dog experienced sudden hypotension and respiratory arrest approximately 8 hours after anaesthesia recovery and died.

Limitations

This was a single case, limiting generalizability. Only single-phase CT was performed; tumour haemodynamics and vascular behaviour could not be assessed fully. No necropsy was performed, preventing definitive determination of metastatic extent or cause of death. The imaging findings could not be correlated with complete post-mortem pathology, and the rapid clinical decline complicated interpretation of systemic involvement.

Conclusions

This report provides the first description of single-phase CT features of a multifocal coalescing form of PHNEC in a French Bulldog. The combination of ultrasonography, CT, laparoscopy, histopathology, and IHC facilitated diagnosis despite the animal’s rapid deterioration. Findings suggest that PHNEC should be included as a differential diagnosis when multiple hyperechoic hepatic nodules on ultrasound correspond with multifocal, coalescing hypoattenuating hepatic nodules on contrast-enhanced CT, particularly when no other primary neoplastic lesions are identified.

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