Which tumor types carry the highest risk of needle-tract or surgical seeding and how should I counsel owners?

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Accepted Answer

Transitional cell carcinoma (TCC) of the urinary bladder carries the highest documented seeding risk among veterinary tumor types, and owners should be counseled that this risk exists for both needle-based procedures and surgical instrumentation.3 For TCC specifically, needle-tract seeding is considered more likely than with other tumors, though the exact incidence in dogs is unknown.3 For context, the incidence in men with prostatic neoplasia following needle procedures is less than 1%, and canine TCC seeding risk is not quantified but has been described in multiple reports.3 Coaxial biopsy techniques carry lower seeding rates than techniques that create a new needle path with each pass, and seeding risk is highest when the needle is withdrawn through the skin after sampling a mass.3 Prostatic carcinoma in dogs is a confirmed seeding risk, with needle-tract seeding documented following both fine-needle aspiration of the prostate and cystocentesis.2 In the reported canine case, a para-preputial cutaneous mass and regional lymphadenopathy consistent with seeding appeared 8 months after the initial procedures.2 Pancreatic carcinoma in cats carries seeding risk even with fine-needle aspiration alone. In the reported feline case, two separate fine-needle aspirations were performed 2 weeks apart, and a subcutaneous nodule consistent with needle-tract seeding appeared on the left ventrolateral abdomen within 2 weeks of subsequent partial pancreatectomy; the cat survived a further 136 days with palliative treatment.1 The authors recommend minimizing the number of needle passes where possible.1 Hepatocellular tumors in dogs represent an additional seeding risk, including the possibility of malignant transformation at the seeding site. In the reported canine case, a hepatocellular adenoma was sampled via core-needle biopsy, and a nodule in the abdominal wall musculature appearing 18 months later was diagnosed as well-differentiated hepatocellular carcinoma, with immunostaini