Spermatocytic seminoma in the rat

Bilateral testicular seminoma in a captive Siberian chipmunk (Tamias sibiricus)

A 5-year-old male Siberian chipmunk (Tamias sibiricus) was presented with marked enlargement of the left testicle. Differential diagnoses included testicular neoplasia such as seminoma, interstitial cell neoplasia, Sertolli cell neoplasia and teratoma or orchitis. Fine needle aspiration of the left testicle was performed under general anesthesia and cytologic findings were consistent with seminoma. Following bilateral orchiectomy, both testicles were examined histologically, revealing bilateral diffuse seminoma. The chipmunk made an uneventful recovery from anesthesia and was treated with analgesics. Follow up two years after surgery, no clinical signs were observed. Seminomas are rare in chipmunks, but orchiectomy may result in long-term disease-free survival as described in other myomorph rodents.

Spontaneous seminoma in medaka (Oryzias latipes)

Although spontaneous development of seminoma is rare in medaka, we encountered spontaneous testicular tumors located within the abdominal cavity in two adult medakas. The growth patterns of the tumors were a combination of solid and cord arrangements in one of the two cases (Case I) and lobular in the other case (Case II). The tumor cells resembled the cells at different stages of spermatogenesis, and a small number of oocyte-like cells were also scattered within the tumor. The tumor with solid and cord patterns showed loss of normal testicular architecture, and the tumor cells had partly invaded the dorsal muscular tissue and metastasized to the liver, kidney, and eye. The tumor with a lobular pattern did not exhibit local invasion or metastasis. The tumors were diagnosed as seminomas based on their histopathological characteristics, and the tumor in Case I was observed to be more malignant than that in Case II.

Proceedings of the 2017 National Toxicology Program Satellite Symposium

The 2017 annual National Toxicology Program Satellite Symposium, entitled "Pathology Potpourri," was held in Montreal, Quebec, Canada at the Society of Toxicologic Pathology's 36th annual meeting. The goal of this symposium was to present and discuss challenging diagnostic pathology and/or nomenclature issues. This article presents summaries of the speakers' talks along with select images that were used by the audience for voting and discussion. Various lesions and other topics covered during the symposium included renal papillary degeneration in perinatally exposed animals, an atriocaval mesothelioma, an unusual presentation of an alveolar-bronchiolar carcinoma, a paraganglioma of the organ of Zuckerkandl (also called an extra-adrenal pheochromocytoma), the use of human muscle samples to illustrate the challenges of manual scoring of fluorescent staining, intertubular spermatocytic seminomas, medical device pathology assessment and discussion of the approval process, collagen-induced arthritis, incisor denticles, ameloblast degeneration and poorly mineralized enamel matrix, connective tissue paragangliomas, microcystin-LR toxicity, perivascular mast cells in the forebrain thalamus unrelated to treatment, and 2 cases that provided a review of the International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) bone nomenclature and recommended application of the terminology in routine nonclinical toxicity studies.

Intratubular spermatocytic seminomas in 2 sprague-dawley rats

This report describes 2 cases of spontaneous intratubular spermatocytic seminomas in Sprague-Dawley rats. These rats were sacrificed at 10 weeks old (case 1) and 40 weeks old (case 2), respectively. Macroscopically, there were no remarkable changes in either case. Microscopically, tumor cells were observed within a single seminiferous tubule (case 1) or several seminiferous tubules (case 2). The proliferating tumor cells were a tripartite cell population comprising small lymphocyte-like, intermediate-sized or large-sized cells, with frequent mitoses, arranged in sheets or forming a basal layer around a tubule or tubules. Immunohistochemically, the tumor cells were strongly positive for proliferating cell nuclear antigen and weakly positive for c-kit, neuron specific enolase and VASA. Our cases provide valuable background control information for the occurrence of seminoma in rats.

Proliferative and nonproliferative lesions of the rat and mouse male reproductive system

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic 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 and differential diagnosis for classifying microscopic lesions observed in the male reproductive system of laboratory rats and mice, with color microphotographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available for society members electronically on the Internet (http://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. A widely accepted and utilized international harmonization of nomenclature for lesions of the male reproductive system 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.

A poorly differentiated germ cell tumor (seminoma) in a Long Evans rat

A large neoplasm that replaced 1 testis of a Long Evans Rat was noted at the final necropsy of a dietary 2-yr study. By light microscopy, the morphological features were consistent with a poorly differentiated seminoma. Ultrastructurally, the cells were polygonal, had a round nucleus, had straight cellular boundaries, and bore no resemblance to Sertoli cells. Although there was little evidence of spermatocytic differentiation, the presence of proacrosomal granules and vesicles, prominent Golgi apparatus, tight intercellular junctions, and a few centriolar pairs without axoneme development, in conjunction with the absence of lipid droplets or abundant smooth endoplasmic reticulum, supported the diagnosis of seminoma rather than Leydig cell tumor. The cells were S-100- and vimentin-positive, although cytokeratin- and alpha-fetoprotein-negative. Seminomas are extremely rare neoplasms in rats; this is the first report in this strain and the first extensive analysis of a rat seminoma without spermatocytic differentiation.

Spermatocytic seminoma

Spermatocytic seminoma is a rare testicular neoplasm that occurs only in adults (range, 25 to 87 years; mean, 54). It has no ovarian homologue and is found only in descended testes. It is not associated with other types of germ cell neoplasia. Orchiectomy is curative in virtually all cases; of more than 200 known cases, only one has metastasized. In a dozen cases sarcomas have arisen in the testes in association with spermatocytic seminoma; most of these patients have died of metastatic sarcoma after short intervals. The gross appearance is characteristically edematous or gelatinous and more than half the tumors have been more than 5 cm in diameter. Microscopically, they are composed of sheets of small, medium, and large cells with spherical nuclei. The chromatin is dense in the small cells and filamentous in the medium and large ones. The cytoplasm is eosinophilic to amphophilic and lacks glycogen. It is not associated with intratubular germ cell neoplasia of the undifferentiated type. Analyses of DNA content have failed to show haploid populations and the lectin binding does not show maturation toward spermatocytes. Differing from seminoma in essentially all characteristics, it is not a variant of seminoma.

Rarely occurring spontaneous metastasizing testicular tumors in rats. Histopathologic and ultrastructural features

Testicular tumors are not uncommon in aging rats. However, metastasis from these neoplasms to several distant visceral organs has not been reported. Testicular tumors were observed in a total of 18 (1.34%) Sprague-Dawley rats out of 1340 males examined. Out of these 18 neoplasms, interstitial tumors were observed in 12 rats, of which 11 were benign and one malignant. Spermatic seminomas were observed in two (0.15%) cases (one benign and one malignant). Both rats with malignant testicular neoplasms were sacrified in extremis. Remaining four tumors were classified as mesotheliomas. Detailed gross, histopathologic and electron microscopic features of primary testicular neoplasms with metastases to several distant visceral organs are described and discussed.

Spermatocytic seminoma: an immunohistochemical study

Spermatocytic seminoma (SS) is an unusual germ cell tumor that behaves in an indolent fashion. Because orchiectomy alone in adequate treatment, it is important to distinguish SS from classic seminoma and other germ cell tumors. Light microscopic distinction usually is possible; however, occasional cases of SS exhibit atypical features, including the presence of a lymphoid infiltrate or microcystic change, which simulate classic seminoma and yolk sac tumor, respectively. Immunohistochemistry might aid in this differential diagnosis, but the immunohistochemical profile of SS is not well reported in the literature. We examined seven SS cases (six men and one non-human primate) with a panel of 14 antibodies directed against placental-like alkaline phosphatase (PLAP), keratins (CAM 5.2, AE1/AE3), vimentin, human chorionic gonadotropin, alpha-fetoprotein, muscle-specific actin, carcinoembryonic antigen, S-100 protein, epithelial membrane antigen, desmin, leukocyte-common antigen, neuron-specific enolase, and human placental lactogen. A previously unreported finding was the presence of focal cytoplasmic staining for low molecular weight cytokeratin (CAM 5.2) in three cases. All other antibodies produced essentially negative results, including anti-PLAP. The PLAP and neuron-specific enolase negativity of SS are in contrast to the positivity of classic seminoma for these markers. A simplified panel of antibodies is recommended to assist in the differentiation of SS from other forms of germ cell neoplasia.

Intratubular spermatic seminoma in a Fischer-344 rat

A case of a spontaneous intratubular spermatic seminoma is described in a 98-wk-old Fischer-344 (F-344) rat. The differential diagnosis of spermatic seminoma from the other morphological forms of the tumor was based on the recognition of 3 cell types. The tumor cells were positive for S-100 antigen and cytokeratin. To the best of our knowledge, this is the second case of a seminoma reported in an F-344 rat and the first dealing with electron microscopic and immunohistochemical features of this tumor.

Proliferative lesions in the male reproductive system of F344 rats and B6C3F1 mice: incidence and classification

The incidences of all primary neoplasms in the testes and accessory reproductive organs of 51,230 male Fischer 344 (F344) rats and 46,752 male B6C3F1 mice were obtained from the pathology data base of more than 300 long-term toxicity/carcinogenicity studies performed for the National Toxicology Program. The overall incidence of reproductive system neoplasms in male F344 rats was 81.5%. The most common neoplasms were interstitial cell adenoma of the testis (76.6%), adenoma/carcinoma of the preputial glands (2.9%), mesothelioma of the tunica vaginalis (1.5%), and adenoma of the prostate gland (0.3%). The combined incidence (0.1%) of 59 other rare neoplasms consisted of 18 different types that occurred with a frequency of 4 or less. In contrast to the rats, male B6C3F1 mice had a low overall incidence (0.6%) of neoplasms in reproductive organs. The most common neoplasm was the interstitial cell adenoma (0.4%). Thirty additional types of neoplasms were identified. Each of these uncommon neoplasms occurred at a frequency of 12 or less with an overall combined incidence of 0.2%. Morphological features are described for neoplasms in the rat and mouse, and criteria are presented for differentiation of testicular interstitial cell adenoma, prostatic adenoma, and mesothelioma from hyperplastic changes.