Needle‐tract seeding following transabdominal ultrasound‐guided fine‐needle aspiration biopsy and cystocentesis of a cytologically diagnosed prostatic carcinoma in a dog

Abstract A 10‐year‐old, neutered, male, mixed‐breed dog underwent ultrasound‐guided fine‐needle aspiration biopsies, leading to cytological suspicion of prostatic carcinoma. A whole‐body computed tomography and computed tomography retrograde urethrography were performed, confirming a mineralised asymmetric heterogenous prostatomegaly, with an invasion of the prostatic urethra and bladder trigonum and suspected distant metastasis to multiple organs. Prostatectomy was not recommended due to the invasiveness of the prostatic neoplasia. Instead, medical treatment with toceranib was installed, which led to clinical improvement for 7 months. Eight months after the medical treatment was started, the dog presented with a new para‐preputial cutaneous mass and regional lymphadenopathy. Fine‐needle aspiration biopsies of the cutaneous mass and right superficial inguinal lymph node were taken. Cytology of the mass and lymph node revealed tumoral epithelial cells compatible with an undifferentiated adenocarcinoma or carcinoma. Given the fact that previous fine‐needle aspiration biopsies of the prostate and a cystocentesis were performed, needle‐tract seeding was highly suspected.