Spontaneous Mammary Adenocarcinoma in a Twelve-week-old Female Sprague-Dawley Rat

Abstract

Spontaneous mammary adenocarcinoma was observed in a 12-week-old female SD rat. A movable mass in the right cervical region was found at 11 weeks of age, and the rat was sacrificed the following week. The mass was located in the vicinity of the right salivary gland and measured 38 mm × 26 mm × 16 mm in gross size. It was a firm whitish mass, with a cut surface that was also whitish in appearance. Histopathologically, neoplastic cells formed glandular structures that contained secreted eosinophilic material. Ultrastructurally, similar secreted material and lipid droplets were in the cytoplasm of the neoplastic cells. Immunohistochemically, the neoplastic cells were positive for cytokeratin 8, cytokeratin 18 and estrogen receptor α. Based on these findings, the tumor was diagnosed as a mammary gland adenocarcinoma, and we therefore conclude that this tumor type can occur spontaneously in female SD rats as young as 12 weeks of age.

Toxicological safety assessment of HempChoice® hemp oil extract; a proprietary extract consisting of a high concentration of cannabidiol (CBD) in addition to other phytocannabinoids and terpenes derived from Cannabis sativaL

“…Both necropsy observations were not considered to be a toxic effect of HempChoice® Hemp Oil Extract. Mammary adenocarcinomas spontaneously occur in female rats at 12-weeks of age and is a common spontaneous neoplasia in female Sprague-Dawley rats [ [41] , [42] , [43] ]. The mammary adenocarcinoma observed in this study occurred in only one rat and is considered a spontaneous occurrence.…”

In vitro and in vivo safety evaluation of Nephure™

“…This was also considered to be unrelated to the test material as it was isolated in nature and occurred at the middle dose. Mammary gland adenocarcinomas have been reported in Sprague-Dawley rats as young as twelve weeks of age ( Kuzutani et al., 2012 ). The age-dependent frequency of mammary adenocarcinoma findings makes it difficult to give robust quantitative statements.…”

A mammary fibroadenoma with terminal end buds-like structures in a 7-week-old male SD rat

“…Mammary tumors occur with a high frequency in female aged Crl:CD (SD) rats, with fibroadenoma being the most common 1 , 2 , 3 . In addition, it is known that mammary tumors occur in young animals of this strain 4 , 5 , and so far, there have been two case reports of adenocarcinoma in young female rats 6 , 7 . However, the incidence of spontaneous mammary tumors in male rats is generally low, and only a few cases have been reported in young male SD rats 4 , 5 , although no detailed histological description has been provided.…”

“…Previous case reports on mammary tumors in young SD rats included adenocarcinomas in females aged 24 weeks (10 weeks at discovery) 6 and 12 weeks (11 weeks at discovery) 7 . In short-term toxicological studies or carcinogenicity studies in rats, no occurrence of mammary tumors in rats younger than 32 weeks has been reported 4 , 5 .…”