Siobhan O’Sullivan
Animal Health Laboratory, University of Guelph, Guelph, ON.
AHL Newsletter 2025;29(2):16.
A 3-year-old male rat with a chronic history of laboured breathing developed acute hematuria/pyuria prior to sudden death. Postmortem examination revealed a 2.0 cm x 2.0 cm firm tan/red mass in the caudal abdomen, involving the seminal vesicles and widely adherent to the urinary bladder. There was also thrombosis of the left atrium of the heart. Histopathology confirmed effacement of the seminal vesicles by an adenocarcinoma which was largely necrotic (Fig. 1). Acute hematuria/pyuria was attributed to this adenocarcinoma, with neutrophils, hemorrhage and bacteria present in the adjacent normal tubules of the seminal vesicles. There was metastasis to one adrenal gland, which was completely effaced by neoplasia. There was also marked chronic degenerative nephropathy and marked metastatic mineralization of the pulmonary parenchyma and blood vessel walls in various tissues (Fig. 2).
Male rats have multiple accessory sex glands; those closest to the urinary bladder are the prostate, ampullary glands, and seminal vesicle. While the seminal vesicles were grossly involved, the size of the neoplasm around the bladder indicates that this adenocarcinoma may have originated in any of the accessory glands. Spontaneous adenocarcinoma of the accessory sex glands is periodically reported in male rats, as it is in most species. Metastatic mineralization was an unexpected finding. Most often the term ‘metastatic’ is used in pathology to refer to the systemic dissemination of neoplasia, but ‘metastatic mineralization’ refers to the systemic deposition of mineral secondary to any disease state that induces hypercalcemia. Some carcinomas are known to induce hypercalcemia and metastatic mineralization; this is a recognized paraneoplastic syndrome known as humoral hypercalcemia of malignancy. Chronic renal disease, also seen in this rat, is a more common cause of metastatic mineralization, and may have been the inciting cause in this case.
Figure 1. Rat, seminal vesicle. The seminal vesicle is effaced by adenocarcinoma. Irregular tubules (arrows) lined by neoplastic epithelial cells contain cell debris, and are embedded in a thick desmoplastic fibrous stroma. H&E stain.
Figure 2. Rat, lung. Metastatic mineralization with irregular deposits of basophilic mineral (arrows) expanding the alveolar interstitium. H&E stain.
References
1. Cullen J, Breen M. An overview of molecular cancer pathogenesis, prognosis, and diagnosis. Tumors of Domestic Animals, 4th ed. Meuten D, 2002, Iowa State Press;15-16.
2. Motohashi M, Wakui S, Takahashi H, et al. Adenocarcinoma of the ampullary glands of the ductus deferens in a Sprague-Dawley rat. Tox Path 2014;43(4):593-599.
3. Teredesai A, Wöhrmann T. Metastasizing seminal vesicle adenocarcinoma in a Wistar rat. J Vet Med 2005;52:131-134.