Granular cell lesions in the distal female reproductive tract of aged Sprague-Dawley rats

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

2-Year animal carcinogenicity results for crisaborole, a novel phosphodiesterase 4 inhibitor for atopic dermatitis

BACKGROUND

Crisaborole is a novel, topical nonsteroidal, anti-inflammatory, phosphodiesterase 4 (PDE4) inhibitor for the treatment of mild to moderate atopic dermatitis.

OBJECTIVE

As part of a nonclinical safety testing program, these 2-year studies tested the carcinogenic potential of crisaborole.

METHODS

Crisaborole ointment, 2%, 5%, or 7%, was applied once daily topically to mice, and crisaborole was administered orally to rats at doses of 30, 100, or 300mg/kg/day for up to 104 weeks. Systemic exposure to crisaborole and its metabolites, moribundity/death, clinical signs, and tumor formation were assessed in each study.

RESULTS

Crisaborole treatment was not tumorigenic in mice at any of the doses administered and did not increase the incidence of neoplastic or nonneoplastic microscopic lesions compared with controls. Oral administration of crisaborole at the high dose (300mg/kg/day) to female rats increased the incidence of treatment-related benign granular cell tumors in the distal reproductive tract (uterus with cervix and vagina) but did not cause moribundity/death.

CONCLUSION

Crisaborole was well tolerated and not tumorigenic in mice. It was not tumorigenic in male rats at 300mg/kg/day at exposures that were 3× the human area under the concentration-time curve (AUC₂₄) and was nontumorigenic in female rats at 100mg/kg/day at exposures that were 1× the human AUC₂₄.

Spontaneous nonneoplastic lesions in control Syrian hamsters in three 24-month long-term carcinogenicity studies

Information about the incidence of spontaneously occurring, nonneoplastic background findings in Syrian hamsters is essential if Syrian hamsters are to be used for toxicity studies. Male and female Syrian hamsters of the strain Han:AURA from the Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM) breeding colony were maintained as control animals for carcinogenicity studies and were examined for the presence of nonneoplastic background findings either when they died or when the study was terminated. The nonneoplastic background lesions observed at an incidence of >50% (high), >25% (moderate), and >10% (low) in either male or female animals or in both sexes in one or more long-term studies are detailed. The results are compared to previous published reports of nonneoplastic, spontaneous background lesions in Syrian hamsters. Background information about the incidence of background lesions in Syrian hamsters on short- and long-term studies is useful to both toxicologists and toxicological pathologists.

Nonproliferative and proliferative lesions of the rat and mouse female reproductive system

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicological Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in the female reproductive tract of laboratory rats and mice, with color photomicrographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and aging lesions as well as lesions induced by exposure to test materials. There is also a section on normal cyclical changes observed in the ovary, uterus, cervix and vagina to compare normal physiological changes with pathological lesions. A widely accepted and utilized international harmonization of nomenclature for female reproductive tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Proceedings of the 2013 National Toxicology Program Satellite Symposium

The 2013 annual National Toxicology Program (NTP) Satellite Symposium, entitled "Pathology Potpourri," was held in Portland, Oregon, in advance of the Society of Toxicologic Pathology's 32nd annual meeting. The goal of the NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers' presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for audience voting and discussion. Some lesions and topics covered during the symposium included a caudal tail vertebra duplication in mice; nephroblastematosis in rats; ectopic C cell tumor in a hamster; granular cell aggregates/tumor in the uterus of a hamster; Pneumocystis carinii in the lung of a rat; iatrogenic chronic inflammation in the lungs of control rats; hepatoblastoma arising within an adenoma in a mouse; humoral hypercalcemia of benignancy in a transgenic mouse; acetaminophen-induced hepatotoxicity in rats; electron microscopy images of iatrogenic intraerythrocytic inclusions in transgenic mice; questionable hepatocellular degeneration/cell death/artifact in rats; atypical endometrial hyperplasia in rats; malignant mixed Müllerian tumors/carcinosarcomas in rats; differential diagnoses of proliferative lesions of the intestine of rodents; and finally obstructive nephropathy caused by melamine poisoning in a rat.

Proceedings of the 2009 National Toxicology Program Satellite Symposium

The National Toxicology Program (NTP) Satellite Symposium is a one-day meeting that is held in conjunction with the annual Society of Toxicologic Pathology (STP) meeting. The topic of the 2009 Symposium was "Tumor Pathology and INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) Nomenclature." The goal of this article is to provide summaries of each speaker's presentation, including the diagnostic or nomenclature issues that were presented, along with a few select images that were used for voting. The results of the voting process and interesting points of discussion that were raised during the presentation are also provided. A supplemental file with voting choices and voting results for each case presented at the symposium is available at http://tpx.sagepub.com/supplemental.

The metrial gland in the rat and its similarities to granular cell tumors

Metrial glands are normal structures located in the mesometrial triangle of the pregnant rat uterus from gestational day (GD) 8 through termination of pregnancy. Metrial glands are composed of a dynamic mixed cell population of granulated metrial gland (GMG) cells, endometrial stromal cells, trophoblasts, blood vessels, and fibroblasts. Collections of similar cells may be seen in association with pseudopregnancy and other hormonal disturbances. Granulated metrial gland cells are the hallmark cell of the metrial gland. They are bone-marrow-derived, perforin-positive, natural killer cells that proliferate in the pregnant uterus. Understanding the normal histogenesis of the metrial gland and recognizing the possible existence of GMG cells and a reactive metrial gland in the nonpregnant state are important when examining any uterine lesion that contains granulated cells. This report demonstrates that the cellular composition, morphology, and immunohistochemical staining profile of normal metrial glands are similar to reported granular cell neoplasms in rats and mice. The possibility of a non-neoplastic lesion involving the metrial gland should be considered when proliferative lesions involving granulated cells are observed in the uterus of mice and rats from nonclinical toxicity studies. Positive immunohistochemical staining for perforin and S100 would assist in the classification of such lesions as a reactive metrial gland or decidual reaction.

Characterization of uterine granular cell tumors in B6C3F1 mice: a histomorphologic, immunohistochemical, and ultrastructural study

The granular cell tumor is most often a benign neoplasm of uncertain origin. Four uterine granular cell tumors in control and treated female B6C3F1 mice were identified in chronic studies at the National Toxicology Program. Two tumors occurred in untreated control animals and 2 in treated animals receiving different compounds. Tissue sections were evaluated histologically and stained with hematoxylin and eosin, periodic acid-Schiff with diastase resistance, Masson's trichrome, toluidine blue, phosphotungstic acid-hematoxylin, and stained immunohistochemically with a panel of antibodies to muscle (desmin, alpha smooth muscle actin), neural (S-100, neuron specific enolase), epithelial (wide-spectrum cytokeratin), and macrophage (F4/80) markers. The main histomorphologic feature of tumor cells was the presence of abundant cytoplasmic eosinophilic granules that stained positive for periodic acid-Schiff with diastase resistance. Tumors varied in appearance and were comprised of sheets and nests of round to polygonal cells with distinct borders. Nuclei were hyperchromatic, pleomorphic, and centrally to eccentrically located and often contained single nucleoli. Occasional multinucleated giant cells were observed. Tumors were pale pink and homogeneous with trichrome stain and negative with toluidine blue. Three tumors had positive to weakly positive immunoreactivity for desmin, and 1 was positive for alpha smooth muscle actin. Expression of S-100, wide-spectrum cytokeratin, and neuron-specific enolase was negative for all tumors. Ultrastructurally, prominent electron-dense cytoplasmic granules were abundant and contained secondary lysosomes with heterogeneous lysosomal contents. The characteristics of these uterine granular cell tumors were suggestive of a myogenic origin.

Granular Cell Tumor in the Testis of a Rabbit: Cytologic, Histologic, Immunohistochemical, and Electron Microscopic Characterization

An adult pet rabbit ( Oryctolagus cuniculus) presented with a progressively enlarging left testicle. Because neoplasia was suspected, the testicle was removed. Pathologic evaluation (exfoliative cytology, histopathology, immunohistochemistry, electron microscopy) indicated that the tumor was an intratesticular granular cell tumor. Granular cell tumor has not been described in rabbits before and has not been described in the testes of animals or postnatal humans. Granular cell tumor should be included as a differential diagnosis of testicular tumors, particularly Leydig cell tumor, because of potential histologic similarities.

Aromatase inhibitors prevent spontaneous granular cell tumors in the distal female reproductive tract of Sprague-Dawley rats

We recently established diagnostic criteria for granular cell changes in the distal female reproductive tract of rats. In a review of control animals from 9 carcinogenicity studies, we found that approximately 23% of animals had granular cell alterations. Because estrogen may play a role in the pathogenesis of granular cell alterations, we reviewed tissue sections from carcinogenicity studies with 2 aromatase inhibitors and found compound-related decreases in the incidence of granular cell changes. Since these aromatase inhibitors selectively prevent the conversion of androgenic steroids to the corresponding estrogens, these data further suggest that estrogen may play a role in the pathogenesis of granular cell tumors of the reproductive tract of rats.