Perineural invasion of a carcinoma in a dog

By Emma Scurrell

The following are H&E sections of incisional biopsies taken from a mass involving the prostate and encompassing the bladder neck in a 11-year-old, male Staffordshire bull terrier.

Fig 1. No normal tissue is present in these biopsy specimens. Sections consist of infiltrative nests of neoplastic epithelium that frequently surround and infiltrate nerve bundles.

Fig 2. No normal tissue is present in these biopsy specimens. Sections consist of infiltrative nests of neoplastic epithelium that frequently surround and infiltrate nerve bundles.

Final Diagnosis

Carcinoma associated with perineural invasion

Discussion

The morphology of the neoplastic infiltrate and the location of the tumour are most suggestive of a transitional cell carcinoma. Perineural invasion (PNI), also known as neurotropic carcinomatous spread, refers to the neoplastic invasion of nerves. It is recognised in the human literature as an important route of metastasis, in addition to lymphatic and haematogenous spread. It is most commonly reported in malignancies of the head and neck (particularly squamous cell carcinomas associated with intracranial extension along nerves), pancreas, large intestine, prostate, biliary tract and stomach.