Histopathological and immunohistochemical characterization of spontaneously occurring uterine deciduomas in young adult rats

Mammary and reproductive tract tumours and tumour-like lesions of 286 small pet mammals: a retrospective study

Small mammals are very popular companion animals, and the incidence of particular tumour types in these animals is the subject of extensive research. We carried out a retrospective and comparative analysis of the incidence of reproductive tract and mammary tumours and tumour-like lesions collected from 103 pet rabbits, 75 pet rats, 71 guinea pigs, 12 mice, 11 hamsters, eight African pygmy hedgehogs, four ferrets and two chinchillas. The results indicate that uterine tumours and tumour-like lesions are common in pet rabbits, guinea pigs and African pygmy hedgehogs. In pet rabbits, the most common uterine tumour was endometrial adenocarcinoma, while in guinea pigs benign lesions predominated (ie, leiomyoma, endometrial adenoma, cystic endometrial hyperplasia and deciduoma). Uterine tumours in African pygmy hedgehogs included adenosarcomas and endometrial polyps. Ovarian lesions were found only in guinea pigs (ovarian rete adenomas, rete cysts) and African pygmy hedgehogs (mostly granulosa cell tumours), while testicular tumours were diagnosed in pet rabbits, one pet rat and one guinea pig. Mammary tumours were common in pet rabbits, pet rats, guinea pigs, mice, hamsters and African pygmy hedgehogs. In pet rats, the most common mammary tumour was fibroadenoma, while in other animals carcinomas predominated. In guinea pigs and, to a lesser extent, in pet rats, a significant percentage of mammary tumours occurred in males. Guinea pigs seem to be predisposed to mammary tumours of ductal origin. This study describes for the first time uterine angioleiomyoma in the pet rabbit and mammary spindle cell carcinoma in the Djungarian hamster and chinchilla.

Morphological and immunohistochemical diversity of endometrial stromal sarcoma in rats

To clarify the histopathological characteristics of rat endometrial stromal sarcoma (ESS), we morphologically reviewed 12 malignant uterine tumors protruding into the lumen in previous rat carcinogenicity studies. The 12 cases were classified into the following 6 types based on their morphological features: spindle cell and collagen rich type, pleomorphic/spindle cell and compact type, decidual alteration type, histiocytic and multinucleated giant cell mixture type, Antoni A-type schwannoma type, and Antoni B-type schwannoma type. Immunohistochemically, tumor cells in all cases exhibited focal or diffuse positive reactions for vimentin, and 11 of the 12 cases were positive for S-100. Interestingly, 9 cases were positive for desmin or αSMA, indicating tumor cells expressing smooth muscle properties. Both Antoni A- and B-type schwannoma types showed low reactions for both muscle markers. Positive results for estrogen receptor α in the 11 cases suggested that they were derived from endometrial stromal cells. On the basis of their immunohistochemical profiles, they were considered to be derived from endometrial stromal cells while they showed morphological variation. The detection of a basement membrane surrounding tumor cells might not be a definitive indicator for differential diagnosis of ESS from malignant schwannoma. In conclusion, ESS could exhibit wide morphological and immunohistochemical variation including features of schwannoma or smooth muscle tumor.

Hoxa-10 and Cyclin D3 Overexpression in the Decidual Reaction in a Superovulation Protocol in Young Adult C57BL/6J Mice

Following the performance of a superovulation protocol, multiple nodules were observed bilaterally in the uterine horns of 31 of 276 (11.2%) C57BL/6 J female mice aged 8.5 ± 0.6 (mean and standard error of mean) weeks. These lesions prevented embryo collection, and the uterine decidual reaction was suspected. Samples of pathological uteri (n = 20) and the normal genital tracts of donors treated with a similar superovulation protocol (control group, n = 10) were collected. Immunohistochemistry was performed to evaluate pancytokeratin, desmin, vimentin, progesterone receptor (PR), estrogen receptor α (ERα), Ki-67, cyclin D3 and c-Myc expression, as well as quantitative polymerase chain reaction to assess cyclin D3, Hoxa-10 and heparin-binding epidermal growth factor-like growth factor (HB-EGF) mRNA expression. The uterine decidual reaction presented a high degree of structural organization and specifically affected the antimesometrial region of the endometrium. The abnormal decidual cells were large polygonal cells that were frequently polyploid or binucleated and strongly positive for desmin. Immunohistochemistry showed higher Ki-67 proliferation index and higher expression of PR and cyclin D3 in decidual cells in the antimesometrial aspect of the endometrium, compared to nondecidualized endometrial stromal cells in the mesometrial aspect of affected uteri, and compared to endometrial stromal cells in healthy uteri. High expression of cyclin D3 and Hoxa-10 mRNA was also observed in uteri affected by the decidual reaction. These results suggest that PR overexpression in endometrial stromal cells, likely due to high progesterone levels, triggers cyclin D3 and Hoxa-10 overexpression, which may be involved in the pathological mechanisms of the mouse uterine decidual reaction.

N-methyl-N-nitrosourea-induced schwannomas in male Sprague-Dawley rats with a literature review of inducible and spontaneous lesions

N-methyl-N-nitrosourea (MNU) possesses peripheral nervous system carcinogenic activity in rats and induces benign and malignant schwannomas in systemic organs. In this retrospective study, we compared the characteristics of various immunohistochemical markers in MNU-induced schwannomas in male Crj:CD(SD)IGS rats including: vimentin (Vim), S100, p75 nerve growth factor receptor (LNGFR), CD57, pancytokeratin (CK), myoglobin, desmin and α smooth muscle actin (SMA). Single intraperitoneal exposures of 50 or 75mg/kg MNU in male rats at the age of 4 weeks induced schwannomas in 43 surviving and terminated rats up to 30-weeks-old. The incidence rate of neoplastic lesions was 37% (16 of 43 rats). Benign schwannomas (mesentery, pancreas, thymus) and malignant schwannomas (subendocardium, cardiac intramural, thoracic cavity, abdominal cavity, prostate), occurred in nine and seven rats, respectively. All neoplastic lesions were moderately or strongly positive for Vim, S100 and LNGFR proteins. Benign tumors were weakly positive and malignant tumors strongly positive for Ki-67, suggesting a high active proliferation rate of Schwann cell precursors. All lesions were negative for CD57, CK, myoglobin, desmin and SMA. This data may provide useful immunohistochemical information for the investigation of schwannomas in rat chemical carcinogenicity studies.

Green Tea Extract-induced Acute Hepatotoxicity in Rats

Although green tea is considered to be a healthy beverage, hepatotoxicity associated with the consumption of green tea extract has been reported. In the present study, we characterized the hepatotoxicity of green tea extract in rats and explored the responsible mechanism. Six-week-old IGS rats received a single intraperitoneal (ip) injection of 200 mg/kg green tea extract (THEA-FLAN 90S). At 8, 24, 48 and 72 hrs and 1 and 3 months after exposure, liver damage was assessed by using blood-chemistry, histopathology, and immunohistochemistry to detect cell death (TUNEL and caspase-3) and proliferative activity (PCNA). Analyses of malondialdehyde (MDA) in serum and the liver and of MDA and thymidine glycol (TG) by immunohistochemistry, as oxidative stress markers, were performed. Placental glutathione S-transferase (GST-P), which is a marker of hepatocarcinogenesis, was also immunohistochemically stained. To examine toxicity at older ages, 200 mg/kg green tea extract was administered to 18-wk-old female rats. In 6-wk-old rats, 12% of males and 50% of females died within 72 hrs. In 18-wk-old rats, 88% died within 72 hrs. The serum levels of aspartate aminotransferase, alanine aminotransferase and/or total bilirubin increased in both males and females. Single-cell necrosis with positive signs of TUNEL and caspase-3 was seen in perilobular hepatocytes from 8 hrs onward in all lobular areas. PCNA-positive hepatocytes increased at 48 hrs. MDA levels in the serum and liver tended to increase, and MDA- and TG-positive hepatocytes were seen immunohistochemically. GST-P–positive hepatocellular altered foci were detected in one female rat at the 3-month time point. In conclusion, a single injection of green tea extract induced acute and severe hepatotoxicity, which might be associated with lipid peroxidation and DNA oxidative stress in hepatocytes.

N -Methyl- N -nitrosourea-induced Renal Tumors in Rats: Immunohistochemical Comparison to Human Wilms Tumors

N-Methyl-N-nitrosourea (MNU)-induced renal tumors in rats and Wilms tumors in humans were compared. Renal mesenchymal tumors (RMTs) and nephroblastomas (blastemal and epithelial components) in female Lewis rats treated with a single intraperitoneal injection of 50 mg/kg MNU at birth and Wilms tumors (blastemal, epithelial and mesenchymal components) in humans were analyzed for the expression of pancytokeratin (CK), vimentin, p63, α-smooth muscle actin (SMA), desmin, S-100, CD57, CD117/c-kit, Wilms tumor 1 protein (WT1) and β-catenin. The mesenchymal components of rat RMTs and human Wilms tumors expressed vimentin, SMA and β-catenin. The blastemal components of rat nephroblastomas and human Wilms tumors expressed vimentin, CD117/c-kit and β-catenin. The epithelial components of rat nephroblastomas and human Wilms tumors expressed vimentin and β-catenin. WT1 was expressed in different cellular components of rat tumors as compared with human Wilms tumors; the expression was seen in mesenchymal tumors and blastemal components of nephroblastomas in rats and epithelial components in human Wilms tumors. CK, p63 and CD57 were not expressed in rat RMTs or nephroblastomas, while CK and WT1 were expressed in epithelial components and CD57 was expressed in blastemal and epithelial components of human Wilms tumors. Rat and human tumors were universally negative for the expression of desmin and S-100. The immunohistochemical characteristics of rat renal tumors and human Wilms tumors may provide valuable information on the differences in renal oncogenesis and biology between the two species.