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

Predominance of Granular Cell Tumours among Testicular Tumours of Rabbits (Oryctolagus cuniculi f. dom.)

Testicular neoplasms are reported rarely in pet and laboratory rabbits (Oryctolagus cuniculi f. dom.), with interstitial cell tumours being the most commonly described testicular neoplasm. In this retrospective study, paraffin wax-embedded testicles with neoplastic changes from 52 rabbits were investigated. Five out of 52 animals exhibited more than one tumour type, resulting in a total of 57 tumours. Granular cell tumours were the most prevalent neoplasm with 36 examples (63%) out of the 57 testicular tumours. Interstitial cell tumours, Sertoli cell tumours and seminomas occurred less frequently. Granular cell tumours of the testis are rare in rabbits. Histological similarities between granular cell and interstitial cell (Leydig cell) tumours in haematoxylin and eosin-stained tissue sections may lead to misdiagnoses. The periodic acid-Schiff reaction or immunohistochemistry for periaxin and S100 protein, as well as ultrastructural analysis, are useful methods to confirm the diagnosis.

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.

Neoplastic and Nonneoplastic Lesions in Aging Mice of Unique and Common Inbred Strains Contribution to Modeling of Human Neoplastic Diseases

The evaluation of spontaneous lesions in classical inbred strains of mice has become increasingly important because genetically engineered mice (GEMs) are created on these backgrounds. Novel inbred strains—genetically diverse from classic strains—are valuable both as a new background for GEM mice and to increase the genetic variation found in laboratory mice. Newly arising spontaneous genetic alterations in commonly used strains may also lead to new and valuable mouse models of disease. This report evaluates gross and histological lesions in relatively new, classic, and rarely explored mouse inbred strains. Pathological lesions of 1273 mice from 12 inbred strains (129S1/SvW, A.CA- H2f/W, AKR/W, BALB/cW, BN/aW, C57BL/6 W, C57BL/10 W, C3H/W, C3H wad/W, CBA/W, DBA/2 W, and WOM/W) are reported. BN/aW, WOM/W, and C3H wad/W are novel inbred strains produced and maintained in the Department of Genetics and Laboratory Animal Breeding at the Center of Oncology, Warsaw, Poland. Both neoplastic and nonneoplastic lesions were examined. The prevalence of lung neoplasms was significantly higher in A.CA- H2f/W (33.3%) and BALB/cW (33.8%) mice ( P < .01). The prevalence of liver neoplasms was significantly higher in the CBA/W strain ( P < .01). Mammary gland neoplasms arose at a greater frequency in C3H/W mice ( P < .01). The occurrence of uterine neoplasms was higher in DBA/W and 129S1/SvW mice. AKR/W and WOM/W mice developed T-cell lymphoblastic lymphoma with high frequency (110/121 [90.9%] and 159/175 [90.9%], respectively) before 1 year of age. The occurrence of nonneoplastic lesions in the kidneys of BN/aW mice was increased ( P < .01).

A collision tumor consisting of granular cell tumor and adenocarcinoma in the uterus of an aged djungarian hamster

A neoplastic nodular lesion consisting of an admixture of granular cell tumor and adenocarcinoma was found in the uterus of a 26-month-old Djungarian hamster. Neoplastic cells of the uterine adenocarcinoma showed an epithelial nature in their growth patterns and by cytokeratin-immunopositive reaction, exhibiting nuclear pleomorphism. The granular cells had an abundant amount of fine granular eosinophilic cytoplasm and eccentric or central nuclei with no nuclear atypia; the granular structures were positive for periodic acid-Schiff with diastase resistance and were confirmed as lysosomes/autophagosomes by electron microscopy; immunohistochemically, the cells reacted to desmin, vimentin and α-smooth muscle actin and negatively for neurogenic, histiocyte/macrophage or epithelial markers, indicating smooth muscle origin. Because these tumors were generated from different cell origins, a diagnosis of collision tumor was made.

Useful immunohistochemical markers of tumor differentiation

Immunohistochemistry (IHC) has been somewhat underutilized in the practice of toxicological pathology but can be a valuable tool for the evaluation of rodent neoplasms, both in a diagnostic and an investigational role. Determining an exact tumor type using standard hematoxylin and eosin (H&E) staining of formalin-fixed tissues can be challenging, especially with metastatic and/or poorly differentiated tumors. Successful IHC is dependent on many factors, including species and tissue type, type and duration of fixation, quality fresh or frozen sectioning, and antibody specificity. The initial approach of most tumor diagnosis IHC applications is distinguishing epithelial from mesenchymal differentiation using vimentin and cytokeratin markers, although false-negative and/or false-positive results may occur. Experimentally, IHC can be employed to investigate the earliest changes in transformed tissues, identifying cellular changes not normally visible with H&E. Individual markers for proliferation, apoptosis, and specific tumor proteins can be used to help distinguish hyperplasia from neoplasia and determine specific tumor origin/type. IHC provides a relatively rapid and simple method to better determine the origin of neoplastic tissue or investigate the behavior or progression of a given neoplasm. Several experimental and diagnostic examples will be presented to illustrate the utility of IHC as a supplement to standard staining techniques.

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.