Spontaneous tumors of the meninges in rats

Primary intracranial fibrosarcoma in a southern sea otter Enhydra lutris nereis

Southern sea otters Enhydra lutris nereis, a threatened marine mammal species, face numerous environmental and infectious disease challenges in their native habitat of coastal California, USA. However, there are few published cases describing neoplasia in sea otters despite their relatively long life span when cared for in aquarium settings. An 18 yr old neutered male southern sea otter, born and raised in human care, presented with an acute onset of seizures and dull mentation. Magnetic resonance imaging of the head revealed a large, central brain lesion. After no improvement with treatment, euthanasia was elected due to a poor prognosis. Grossly, a poorly demarcated, granular, tan mass expanded the cranial meninges in the longitudinal fissure at the level of the cruciate sulcus and extended into the underlying gray matter and superficial white matter. Histologically, the mass was composed of spindle cells, forming haphazardly arranged interlacing bundles and herringbone patterns, with a high mitotic count, moderate cellular pleomorphism, and prominent vascularization. Neoplastic cells demonstrated positive immunoreactivity for vimentin and negative immunoreactivity for smooth muscle actin, factor VIII-related antigen, S100, melan-A, E-cadherin, desmin, glial fibrillary acidic protein, and cytokeratin AE1/AE3. Based on gross, histologic, and immunohistochemical findings, the mass was most consistent with a primary intracranial fibrosarcoma (PIF). PIFs are a rare neoplasm in both humans and other animals with few reports in the veterinary literature. This is the first recorded case of a PIF in a sea otter.

Spontaneous meningioma in a pig-tailed macaque (Macaca nemestrina)

We present a case of spontaneous meningioma in a female pig-tailed macaque (Macaca nemestrina) more than 24 years old. Clinically, the monkey displayed slow, weak, and insecure movements and poor vision. A tumorous mass was present at the floor of the cranial vault extending from the optic chiasm towards the foramen magnum. It compressed adjacent parts of the brain, infiltrated the sphenoidal and occipital bone, and showed transcranial expansion into the pharyngeal area. Histologically, the tumor was consistent with a meningioma displaying mostly meningothelial and some microcystic components. Since only six cases of meningiomas in nonhuman primates have been reported so far and only two of these meningiomas have been described in detail, the findings of each case should be reported to expand the knowledge base of this type of tumor. In addition, this is the first description of a meningioma in pig-tailed macaques.

Findings in Historical Control Harlan RCCHan™

Vehicle control Harlan RCCHan™:WIST rats were examined to provide control data for subsequent studies. The rats (180 male and 180 female) were dosed daily via oral gavage with reverse osmosis water for up to 104 weeks. At necropsy, body weights and macroscopic findings were recorded and tissues were collected for histopathology. The mean body weight at terminal sacrifice was 687 g for males and 466 g for females. The overall survival rate was 62% for males and 59% for females. The most common cause of death for males and females found dead or examined following unscheduled euthanasia was pituitary neoplasia with an incidence of 13.9% for males and 18.9% for females. Macroscopic and neoplastic and nonneoplastic microscopic findings are presented by body system.

Proliferative and nonproliferative lesions of the rat and mouse central and peripheral nervous systems

Harmonization of diagnostic nomenclature used in the pathology analysis of tissues from rodent toxicity studies will enhance the comparability and consistency of data sets from different laboratories worldwide. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of four major societies of toxicologic pathology to develop a globally recognized nomenclature for proliferative and nonproliferative lesions in rodents. This article recommends standardized terms for classifying changes observed in tissues of the mouse and rat central (CNS) and peripheral (PNS) nervous systems. Sources of material include academic, government, and industrial histopathology databases from around the world. Covered lesions include frequent, spontaneous, and aging-related changes as well as principal toxicant-induced findings. Common artifacts that might be confused with genuine lesions are also illustrated. The neural nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).

Long-term safety of single and multiple infrared transcranial laser treatments in Sprague-Dawley rats

BACKGROUND AND OBJECTIVE

Growing interest exists in the use of near-infrared laser therapies for the treatment of numerous neurologic conditions, including acute ischemic stroke, traumatic brain injury, Parkinson's disease, and Alzheimer's disease. In consideration of these trends, the objective of this study was to evaluate the long-term safety of transcranial laser therapy with continuous-wave (CW) near-infrared laser light (wavelength, 808 ± 10 nm, 2-mm diameter) with a nominal radiant power of 70 mW; power density, 2,230 mW/cm(2), and energy density, 268 J/cm(2) at the scalp (10 mW/cm(2) and 1.2 J/cm(2) at the cerebral cortical surface) in healthy Sprague-Dawley rats.

MATERIALS AND METHODS

In this study, 120 anesthetized rats received sequential transcranial laser treatments to the right and left parietal areas of the head on the same day (minimum of 5 min between irradiation of each side), on either Day 1 or on each of Days 1, 3, and 5. Sixty anesthetized rats served as sham controls. Rats were evaluated 1 year after treatment for abnormalities in clinical hematology and brain and pituitary gland histopathology.

RESULTS

No toxicologically important differences were found in the clinical hematology results between sham-control and laser-treated rats for any hematologic parameters examined. All values fell within historic control reference ranges for aged Sprague-Dawley rats. Similarly, brain and pituitary gland histopathology showed no treatment-related abnormalities or induced neoplasia.

CONCLUSIONS

Single and multiple applications of transcranial laser therapy with 808-nm CW laser light at a nominal power density of 10 mW/cm(2) at the surface of the cerebral cortex appears to be safe in Sprague-Dawley rats 1 year after treatment.

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.

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.

Intracranial Granular Cell Tumor in a Dog

A 12-year-old female miniature poodle showed a 3-month history of neurological signs. Magnetic resonance imaging disclosed a high intensity tumor mass in the right cerebral hemisphere with compression of the lateral ventricle. At necropsy, a 2 x 3 cm white, friable mass was found in the right ventral pyriform lobe. Microscopically, the tumor cells were large, polygonal to round cells supported by a sparse fibrovascular stroma. The tumor cells typically possessed finely granular, pale eosinophilic cytoplasm with strongly positive periodic acid-Schiff (PAS) reaction. The tumor cells were immunopositive for vimentin, NSE and S-100. Ultrastructurally, the tumor cells showed large amounts of granules in the cytoplasm, and absence of basement membrane. Based on the above-mentioned findings, the intracranial granular cell tumor was diagnosed.

Granular cell tumor of the canine central nervous system: two cases

Although pure granular cell tumors have been reported in various sites in the dog, only one tumor has been reported in the central nervous system. Two dogs presented with neurologic signs had brain lesions detected by magnetic resonance imaging in the area of the olfactory bulbs and frontal cortex. In both dogs, a clinical diagnosis of a granular cell tumor was made from tissues obtained from stereotactic biopsies guided by computed tomography. Surgical removal of the tumors was followed by histopathologic, ultrastructural, and immunocytochemical characterization. Although not conclusive, these studies indicated that the granular cells were not of leucocyte origin but may have been derived from the meninges. One dog died 12 months after surgery, and the other was alive 4 months later.

Nine cases of granular cell tumors in B6C3F1 mice

The histological characteristics of 9 cases of granular cell tumors (GCTs) observed in B6C3F1 mice were examined to determine their cellular origin. Seven of the 9 cases were found in the uterus and other 2 cases were in the subcutaneous tissue. Tumor cells had abundant granules in the cytoplasm which were stained with PAS and were resistant to diastase treatment. Ultrastructurally, the granules were identified as lysosomes. The cell surface had cytoplasmic processus showing interdigitation with adjacent cells. A character feature of the tumor cells was the presence of a desmosome-like structure on their cell surface but no basal lamina was demonstrated. Although GCTs have been considered to be derived from Schwann cells on the basis of their ultrastructural features and S-100 protein-immunopositive findings, the absence of basal lamina in the present cases may raise a controversy as to their origin.

Morphologic characterization of spontaneous nervous system tumors in mice and rats

Spontaneous rodent nervous system tumors, in comparison to those of man, are less well differentiated. Among the central nervous system (CNS) tumors, the "embryonic" forms (medulloblastoma, pineoblastoma) occur both in rodents and humans, whereas the human "adult" forms (gliomas, ependymomas, meningiomas) have fewer counterparts in rodents. In general, the incidence of spontaneous CNS tumors is higher in rats (>1%) than in mice (>0.001%). A characteristic rat CNS tumor is the granular cell tumor. Usually it is associated with the meninges, and most meningeal tumors in rats seem to be totally or at least partly composed of granular cells, which have eosinophilic granular cytoplasm, are periodic acid-Schiff reaction (PAS)-positive, and contain lysosomes. Such tumors are frequently found on the cerebellar surface or at the brain basis. Rat astrocytomas are diffuse, frequently multifocal, and they invade perivascular spaces and meninges. The neoplastic cells with round to oval nuclei and indistinct cytoplasm grow around preexisting neurons, producing satellitosis. In large tumors, there are necrotic areas surrounded by palisading cells. Extensive damage of brain tissue is associated with the presence of scavenger cells that react positively with histiocytic/macrophage markers. The neoplastic astrocytes do not stain positively for glial fibrillary acidic protein; they probably represent an immature phenotype. In contrast to neoplastic oligodendroglia, they bind the lectin RCA-1. Astrocytomas are frequently located in the brain stem, especially the basal ganglia. Rat oligodendroglial tumors are well circumscribed and frequently grow in the walls of brain ventricles. Their cells have water-clear cytoplasm and round, dark-staining nuclei. Atypical vascular endothelial proliferation occurs, especially at the tumor periphery. Occasionally in the oligodendrogliomas, primitive glial elements with large nuclei occur in the form of cell groups that form rows and circles. Primitive neuroectodermal tumors of rats, such as pineal tumors or medulloblastomas, appear to have features similar to those found in man. In mice, the meningeal tumors are mostly devoid of granular cells and the astrocytomas are similar to those occurring in rats, whereas spontaneous oligodendrogliomas are observed extremely rarely. Tumorlike lesions, such as lipomatous hamartomas or epidermoid cysts, are occasionally encountered in the mouse CNS. It is suggested that we classify rodent CNS lesions as "low grade" and "high grade" rather than as "benign" and "malignant." The size of CNS tumors is generally related to their malignancy. Tumors of the peripheral nervous system are schwannomas and neurofibromas or neurofibrosarcomas consisting of Schwann cells, fibroblasts, and perineural cells. Well-differentiated schwannomas are characterized by S-100 positivity and the presence of basement membrane. They show either Antoni A pattern with fusiform palisading cells or Antoni B pattern, which is sparsely cellular and has a clear matrix. The rat develops specific forms of schwannomas in the areas of the submandibular salivary gland, the external ear, the orbit, and the endocardium. Spontaneous ganglioneuromas occur in the rat adrenal medulla or thyroid gland. Compared to experimentally induced neoplasms, the spontaneous tumors of the rodent nervous system are poor and impractical models of human disease, although they may serve as general indicators of the carcinogenic potential of tested chemicals.

Morphological and ultrastructural study of the histogenesis of meningeal granular cell tumors in rats

To clarify the cell of origin of granular cell tumors in the rat brain, light and/or electron microscopic examinations were performed on 40 cases of spontaneous meningeal tumors in Wistar (Jcl: Wistar) rats. The meningeal tumors were histologically subclassified into 3 types: meningothelial meningiomas (MMs), 3 cases; granular cell tumors (GCTs), 28 cases; and mixed forms (MIXs) of GCTs and MMs, 9 cases. Of these tumors, 2 MMs, 2 GCTs, and 3 MIXs were examined by transmission electron microscopy. Tumor cells of MMs were characterized by cytoplasmic intermediate filaments and prominent interdigitating cell processes often connected with cellular junctions without surrounding basal laminae. GCTs were composed of 2 cell types: granular cells with many dense bodies and filamentous cells with fine intermediate filaments. MIXs consisted of granular cells, filamentous cells, and intermediate cells. The tumor cells in GCTs and MIXs were apposed to each other and connected with cellular junctions. MIXs displayed a spectrum of cellular differentiation in that 2 MIXs had a close morphological resemblance to GCTs and the other one to MMs. These findings indicate there might be a histogenetic sequence among MMs, GCTs, and MIXs. The present study supports the suggestion that GCTs and MIXs may be variants of MMs from the meningeal arachnoid cell.

Granular cell change in astrocytic tumors

Intracerebral granular cell neoplasms are uncommon. We report five hemispheric astrocytomas, all of which showed the distinctive features of granular cell change, being composed exclusively or predominantly of rounded cells with coarse granular eosinophilic cytoplasm and eccentrically placed nuclei. Four showed clear foci of transition from an anaplastic astrocytoma and contained lipidized as well as granular cells. In all tumors, the cytoplasmic granules were positive for periodic acid Schiff and resistant to diastase digestion, and there was focal glial fibrillary acidic protein expression. In addition, diffuse cytoplasmic positivity with epithelial membrane antigen antiserum was present, but in no case was there true membrane staining. Ultrastructural appearances were similar in four cases, showing the cytoplasm of tumor cells to be filled with membrane-bound autophagic vacuoles; bundles of intermediate filaments were also seen in some cells. Despite earlier controversy over the histogenesis of granular cell tumors, it is now clear that granular change is a degenerative phenomenon that, like lipidization, can occur in tumors of different cell types, including--rarely--astrocytic neoplasms. It is important that this histologic variant be recognized, as on a small biopsy sample diagnostic confusion with an infarct, demyelinating disease or a secondary carcinoma is a real possibility.

Spontaneous equine pulmonary granular cell tumors: morphologic, histochemical, and immunohistochemical characterization

Spontaneous equine pulmonary granular cell tumors were diagnosed in six mature horses at slaughter. These tumors were grossly recognized as multiple (5/6) or single (1/6) creamy white, firm nodules. The tumors, located adjacent to bronchi and bronchioles, often invaded airways, resulting in partial to complete occlusion of the lumina. Neoplastic cells were rounded to polyhedral with numerous eosinophilic cytoplasmic granules that reacted uniformly positive with S-100 and neuron-specific enolase antibodies and multifocally with glial fibrillary acidic protein antibodies. These cells were negative for muscle-specific actin, lysozyme, cytokeratin, chromogranin A, and myelin basic protein antigens and did not stain with silver by the Grimelius technique. Uniformly blue-green and scattered pink intracytoplasmic granules were evident with luxol fast blue and periodic acid-Schiff counterstain for myelin and myelin breakdown products. Histochemical and immunohistochemical staining results of these tumors suggest that they are composed primarily of myelinating Schwann cells with lesser numbers of scattered nonmyelinating Schwann cells. The morphologic features of the equine pulmonary granular cell tumors are strikingly similar to those of endobronchial granular cell tumors of human beings.

Spontaneous osteosarcoma of the meninges in an albino rat

A search of the rat tumor literature revealed no papers on naturally occurring primary osteosarcoma of meninges. In humans, this tumor, arising primarily from the meninges, is unusual; only two cases have been reported. We report on a spontaneously occurring osteosarcoma arising from meninges in a 2-year-old female albino rat. The diagnosis was made on the basis of gross, microscopic, and ultrastructural findings. The diagnosis of this neoplasm is supported by the fact that a primitive mesenchymal cell in the meninges is capable of giving rise to a wide variety of neoplasms.

Biological behaviour and morphological characteristics of a transplantable tumour (MM-KMY) derived from a malignant meningioma in an F344 rat

A subcutaneously transplantable meningeal tumour (MM-KMY) was derived from a spontaneous malignant meningioma which developed in the cerebellar meninges of a female F344 rat. MM-KMY was subjected to 25 serial passages in syngeneic male and female rats. The transplants grew in 8 weeks into a nodule with an average diameter of 5.7 cm and average weight of 125.2 g. MM-KMY possessed large cysts containing fluid and necrotic tissue. Metastases frequently occurred in the lungs of MM-KMY-bearing rats. Histologically, both the original tumour and MM-KMY consisted of round to fusiform neoplastic cells of varying size, with nuclear pleomorphism. Mitotic figures occurred frequently. MM-KMY cells were positive for vimentin. Ultrastructurally, the cells showed desmosome-like structures, interdigitating processes and cytoplasmic intermediate filaments, suggesting an arachnoid cell origin. Abnormal accumulations of hyaline droplets in renal tubular epithelial cells were frequently observed in MM-KMY-bearing rats, suggesting overload of low molecular proteins in the renal tubules. The droplets gave a faint immunoreaction for lysozyme. The relation between the appearance of renal tubular hyaline droplets and the growth of MM-KMY remains to be determined. MM-KMY may prove useful for studying the biological behaviour and morphogenesis of meningeal tumours.

Histologic and immunohistochemical studies of granular cell tumors in seven dogs, three cats, one horse, and one bird

In a retrospective study, granular cell tumors in six dogs (Nos. 1-6), three cats (Nos. 1-3), one horse (No. 1), and one cockatiel (Nymphicus hollandicus) (No. 1) and a meningioma with a granular cell component in one dog (No. 7) were examined histologically and immunohistochemically. These tumors were identified by histologic examination of surgical biopsy specimens, except in the horse, in which the tumor was an incidental finding at necropsy. These diagnoses were initially made by more than one pathologist. Five of the six granular cell tumors in the dogs were in the oral cavity; one of these was in the maxillary gingiva of a 6-month-old puppy. The tumors in the cats were located in the tongue, vulva, and digit. The tumor in the horse was in the lung, and the tumor in the cockatiel was in the periocular tissue. Histologically, all granular cell tumors were characterized by oval to polygonal cells of various sizes. The cells had abundant, pale, eosinophilic cytoplasm with distinct intracytoplasmic granules, distinct cell margins, and mostly central nuclei. In the dogs, the gingival tumor had a large amount of collagen tissue, the tumor in the tongue had dilated blood vessels, and the maxillary tumor in the puppy was more cellular than the other tumors. The tumors in the cats were more anaplastic than the other tumors; one, located in the digit, was considered malignant. The granules in all of the tumors stained with periodic acid-Schiff and were diastase resistant. On staining with Luxol fast blue, the granules of all tumors stained different shades of pink, with the exception of the tumor in the tongue of a cat, which stained bluish green. Immunocytochemically, all tumors except the tumor in the cockatiel reacted against antibodies to vimentin. The granular cell tumor in the lung of the horse and the intracranial meningioma in a dog reacted to the antibody S-100 protein; the tumor in the horse reacted to neuron-specific enolase; tumors in two dogs (gingiva and skin) reacted to L-antitrypsin, and the maxillary tumor also reacted to lysozyme; the malignant tumor in the digit of a cat and the periocular tumor in the cockatiel reacted to muscle common actin and actin; the tumor in the cockatiel also reacted to desmin. Results of these immunocytochemical studies suggest that granular cell tumors, like tumors composed of rhabdoid cells, clear cells, and oncocytes, can have similar morphologic features but be of different cellular origins.

Incidence of brain tumours in rats exposed to an aerosol of 239PuO2

Incidence of brain tumours was investigated in 3390 female and male Wistar rats exposed to an aerosol of 239PuO2, or as sham-exposed controls. Lung doses ranged from 0.05 to 22 Gy. In females, six brain tumours were found in 1058 control rats (incidence, 0.6%) and 24 brain tumours in 2134 rats exposed to Pu (incidence, 1.1%); the survival-adjusted level of significance was p = 0.29 for comparing control with exposed females. In males, two brain tumours were found in 60 control rats (incidence, 3.3%) and seven brain tumours in 138 rats exposed to Pu (incidence, 5.1%); the survival-adjusted level of significance was p = 0.33. Brain tumour incidence was about five times greater in male than in female rats (p = 0.0001), demonstrating a highly significant sex difference in brain tumour incidence. Tumour types were distributed similarly among control and Pu-exposed groups of both sexes; most tumours were astrocytomas. Mean lifespans for rats with brain tumours were not significantly different between control and Pu-exposed rats. Plutonium was not detected on autoradiograms of the brain. These results, like those for plutonium workers, show an increase of brain tumours which cannot be demonstrated statistically to be related to radiation exposure.

Granular cell brain tumors of the laboratory rat: an immunohistochemical approach

We have studied paraffin-embedded specimens of 17 rat granular cell brain tumors (GCBT) from four long-term drug safety carcinogenicity studies by peroxidase-antiperoxidase (PAP) immunohistochemistry with either polyvalent or monoclonal antibodies against glial fibrillary acidic protein (GFAP), S-100 protein (S-100), Leu-7 epitopes, vimentin (VIM), keratin, desmin, and myelin basic protein. We have found that 9 of the 17 GCBT contained GFAP-positive, S-100-positive, and VIM-positive astrocytes, while GFAP-positive and VIM-positive granular cells were observed in 5 of these 9 tumors. Our findings indicate that astroglial cells are involved in rat GCBT and suggest that an astrocytic origin should be considered for these neoplasms.