Intracranial meningioma with polygonal granular cell appearance in a Chihuahua

A menigioma with polygonal granular cell proliferation in an 11-year and 8-month-old male Chihuahua is described. The tumor was observed under the dura matter of the right cerebrum. Microscopically, the tumor consisted of solid growth foci of small- or large- sized polygonal cells, with pale-stained nuclei, prominent nucleoli, and fine granular to foamy eosinophilic cytoplasm. Some of the proliferating cells contained variable amounts of cytoplasmic PAS-positive granules. Immunohistochemical analysis revealed that neoplastic cells were positive for vimentin and S-100 protein. Ultrastructurally, the neoplastic cells contained vesicular structures with a few small round-shaped bodies in the cytoplasm. We diagnosed the case as canine meningioma with granular cell appearance.     

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.     

Thymoma and multiple thymic cysts in a dog with acquired myasthenia gravis

An anterior mediastinal cystic lesion in an 11-year-old mongrel dog was examined. The dog showed dysbasia and vomiting due to megaoesophagus, and anterior mediastinal round mass lesion, approximately 35 mm in diameter, was found by X ray. Based on clinical examinations, the dog was diagnosed as acquired myasthenia gravis and was successfully controlled by anticholinesterase treatment for approximately 4 months. The dog died of thermic stroke and was necropsied. Grossly, fatty tissues with cysts containing yellowish fluid and white nodules were found in the anterior mediastinal area. Histopathologically, multiple cysts, neoplastic tissues, and atrophic thymus were found within the examined tissues. The cysts were lined by thin wall consisting of ciliated long cuboidal and non-ciliated round cells and were filled with eosinophilic colloidal fluid. Some extended cysts contained neoplastic foci within their lumen and walls. The neoplastic tissues consisted of mixed population of large epithelial cells with abundant clear cytoplasm and large oval nuclei, and lymphocytes. Immunohistochemically, proliferating epithelial cells were intensely positive for keratin and cytokeratin, and more than half number of infiltrating lymphocytes were intensely positive for CD3 suggesting T cells. All these findings indicate the neoplastic lesion is thymoma and multiple cysts are considered as thymic or brachial cleft cysts.     

Feline cystic thymoma: a clinicopathologic,immunohistologic, and electron microscopic study of 14 cases

Cystic thymoma was diagnosed in 14 cats in a period of 6 years. The most common clinical sign was laboured breathing. The tumours were characterized by various-sized cystic spaces with central vessels. The epithelial cells varied from oval to spindle to polygonal cells enclosing cystic spaces or in pure epithelial cell components. The nuclei of the neoplastic cells had scattered chromatin and small nucleoli. The cytoplasm was pale eosinophilic. The concentration of mature lymphocytes varied from area to area with rare germinal centres. Immunohistochemically, the epithelial cells stained only with AE(1)/AE(3). The central vessels were positive for vimentin, smooth muscle actin, and factor VIII antigen. Electron microscopy revealed that the cyst walls were lined by epithelial cells that were joined by desmosomes, and the walls were well separated from the cystic spaces by a well-defined basement membrane. The neoplastic epithelial cells contained scattered tonofilaments. Three of the cats had metastasis to the lymph nodes and lungs. Two novel cases of ectopic cystic thymoma have also been described. Results of this study reveal that cystic thymoma is uncommon in cats, and that the histomorphologic, immunohistochemical, and electron microscopic features are similar to those of cystic thymoma in humans.     

Cystic cholangioma in the thoracic cavity of a rat

A female congenic rat produced by repeated backcrossing of Nihon rats, a model for hereditary renal cell carcinoma, to Brown Norway rats was necropsied at 24 months of age. At necropsy, a white mass about 1 centimeter in size was observed in the thoracic cavity, and the mass partly adhered to the esophagus and the diaphragm. Histologically, the mass was clearly circumscribed by connective tissue, and consisted of neoplastic cuboidal epithelial cells that showed cystic tubular proliferation. Some islands of well-differentiated hepatocytes and some vessels were observed in the mass. Immunohistochemically, the tumor cells were strongly positive for cytokeratin and partly positive for vimentin but were negative for mesothelin and Von Willebrand Factor. The positive rate for Ki-67 was 2.4%. Based on these histological and immunohistochemical evidences, we diagnosed this tumor as a cystic cholangioma that might have arisen from the ectopic hepatic tissue in the thoracic cavity.     

Hepatoblastoma in a cat

Hepatoblastomas are neoplasms that originate from putative pluripotential stem cells of the liver. A hepatic mass from an 8-year-old Abyssinian cat was composed of cords and sheets of neoplastic cells, with scattered rosettes and small ductal structures. Most neoplastic cells had a pale eosinophilic cytoplasm and a round to ovoid nucleus. The tumor also had short spindle cells with an oval nucleus. Immunohistochemically, neoplastic cells were weakly positive for embryonic hepatocellular markers, such as alpha-fetoprotein and cytokeratin (CK) 8/18, but negative for the hepatocellular marker Hepatocyte Paraffin 1. The cells were also positive for CD56/neural cell adhesion molecule and for the biliary epithelial markers CK 7, CK 8/18, CK CAM5.2, and vimentin, but negative for CK 20. Some neoplastic cells expressed neuroectodermal or neuroendocrine markers, such as protein gene product 9.5 and synaptophysin, but were negative for chromogranin A and not argyrophilic by the Grimelius technique. The cat died soon after the biopsy without clinical improvement.     

Thymic carcinoma of the thymic hormone secretory type in a cow.

An 8-year-old Holstein cow had tumor nodules and enlarged lymph nodes in the mediastinum, and metastatic tumor masses in the pelvic cavity. The neoplastic cells were characterized by squamous features and intracytoplasmic vacuoles carrying microvilli, some of which contained periodic acid Schiff-positive globular cores, but tubular structures or goblet cells were absent. Many neoplastic cells stained positively for keratin, and occasional cells were positive for thymosin. The presence of secretory granules in the cytoplasm was confirmed by electron microscopy. This neoplasm was considered to be of thymic hormone-secreting epithelial cell origin.     

Small intestine large granular lymphoma in a horse

A 12-year-old Appaloosa gelding was referred to the Texas Veterinary Medical Center with a history of chronic diarrhea and weight loss. At necropsy, numerous oval, craterlike ulcers were observed throughout the small intestine. Histologically, these lesions were composed of a neoplastic proliferation of round cells with intracytoplasmic phosphotungstic acid-hematoxylin-positive granules. The tumor cells stained positively for the CD3 antigen and negatively for a B-cell marker. A diagnosis of large granular lymphoma was based on the morphologic and immunohistochemical characteristics of the neoplasm. The postmortem presentation of this case depicted unusual multifocal, ulcerative lymphomatous lesions throughout the small intestine without involvement of the regional lymph nodes. The histologic and ultrastructural morphology of the neoplastic lymphocytes was similar to that in previously reported cases of abdominal equine large granular lymphomas, but in this case the neoplasm was restricted to the small intestine.     

Primary cardiac granular cell tumor in a dog

The histological, histochemical, and ultrastructural features of a granular cell tumor in the wall of the right atrium of the heart in a nine-year-old dog are described. The histologic appearance of the mass varied from areas of spindle-shaped cells to sheets of globoid cells with foamy granular cytoplasm. The globoid neoplastic cells contained numerous cytoplasmic granules which were variably positive to periodic acid-Schiff staining, with and without disastase digestion. Ultrastructurally, the globoid cells had numerous various-sized, heterogeneous lysosomes with pleomorphic content. A granular cell tumor originating in the heart has not been reported previously in animals. The support for a neural origin of these tumors by the recent identification of several nervous tissue specific proteins in their granular cells is discussed.     

Granular cell variants in a rat schwannoma. Evidence of neurogenic origin of granular cell tumor (myoblastoma).

A large, intraabdominal rat schwannoma had numerous granule-containing cells cytologically identical to cells of granular cell tumor (myoblastoma). The small eosinophilic granules stained positively by the periodic acid-Schiff (PAS) reaction, with intensity not reduced by diastase pretreatment. Granules stained positively with the Tibor Pap silver impregnation for reticulin and by electron microscopy were identical to myoblastoma cell granules. The nuclei of granular cells were morphologically identical to those of the neoplastic Schwann cells. The granular cells were in numerous foci within the tumor, frequently were seen in mitosis, and possessed an extremely variable volume of cytoplasm. They seemed to evolve from neoplastic Schwann cells. Cells with only a narrow perinuclear rim of granular cytoplasm were of the same size and general configuration as adjacent neoplastic Schwann cells, while cells with increasing volumes of granular cytoplasm were increasingly swollen and round. One area of the tumor was composed almost entirely of such large cells and was histologically identical to classic granular cell tumor.     

Adenocarcinoma of apocrine sweat glands in a mouflon (Ovis musimon).

A free-living mouflon (Ovis musimon) was presented with a mass on the left shoulder. At necropsy, multifocal, slightly protruding whitish spots were noted on the kidneys, and several lymph nodes were abnormal. Histologically, the mass was composed of epithelial cells arranged in tubular and tubulopapillary structures. The cytoplasm of the epithelial cells had numerous periodic acid-Schiff-positive and diastase-resistant granules. Ultrastructurally, the cytoplasm of the neoplastic cells contained numerous pleomorphic secretory granules and microvilli, which partially covered the luminal surface of the tumor cells. Metastatic foci were present in prescapular and mediastinal lymph nodes and kidneys. On the basis of histological and ultrastructural findings, this tumor was diagnosed as a tubulopapillary adenocarcinoma, arising from apocrine sweat glands of the skin.     

Mixed thymoma in a cow.

A neoplastic mass measuring 25 x 8 x 3 cm was found in the mediastinum of a 10-year-old Holstein cow. The neoplasm was encapsulated, multilobulated, and cystic. Several firm adhesions were present between the neoplasm and the right cranial lung lobe and the ipsilateral side of the pericardial sac. Under microscopic examination, the neoplasm was characterized by solid sheets of spindle epithelial cells (pancytokeratin and high molecular weight cytokeratin positive) subdivided by fibrous trabeculae. Numerous individualized or small aggregates of mature T-cell (CD3 positive) lymphocytes were scattered throughout the neoplastic cell population. Based on the gross, histologic, and immunohistochemical findings, the neoplasm was diagnosed as a mixed thymoma.     

Cutaneous lymphoplasmacytic lymphoma with systemic metastasis in a cat

A lymphoplasmacytic lymphoma was diagnosed in a 12- year-old domestic cat that had a primary cutaneous mass involving the stomach, liver, kidneys, heart, abdominal wall, diaphragm, bone marrow and several lymph nodes. Histopathologically, the most characteristic feature of this tumor was the heterogeneity of cell components, such as small lymphocytes, well-differentiated plasma cells and plasmacytoid transformed lymphocytes. Amyloid was deposited in the skin, stomach, and several lymph nodes. Immunohistochemically, neoplastic small lymphocytes were positive for CD20, and well-differentiated plasma cells and plasmacytoid transformed lymphocytes were positive for λ-Ig light chains and MUM1/IRF-4. These results emphasize the importance of lymphoplasmacytic lymphoma as a differential diagnosis of extramedullary cutaneous plasmacytoma in cats.     

Renal Cystic Adenocarcinoma in a Flowerhorn Cichlid with Metastatic Involvement of the Spleen

Abstract

A 480-g flowerhorn cichlid (an ornamental hybrid) with severe bilateral abdominal swelling, bulla-like structures on the skin, bilateral exophthalmia, and a prolapsed intestine was presented. Radiographs showed compression of the posterior part of the swim bladder and abdominal distention. Ultrasonography of visceral organs revealed a heterogeneous mass with hypoechoic to anechoic polycystic parenchyma and free fluid in the abdominal cavity. At necropsy, free fluid in the abdominal cavity and a large polycystic mass originating from the posterior kidney were observed. Histologically, the mass was composed of more cystic growth of tubules. The renal architecture was replaced by tubules, often irregular in shape, lined by simple to lightly stratified layers of neoplastic and pleomorphic cuboidal to columnar epithelial cells and the absence of glomeruli. Birefringent crystals were observed with polarized light within the lumen of some tubules. The apical border of the neoplastic cells was periodic acid–Schiff positive. Immunohistochemically, the neoplastic cells were positive for cytokeratin AE1/AE3 and proliferating cell nuclear antigen and were negative for p53 (tumor suppressor protein). Microscopic metastasis was seen in the spleen. The metastatic tumor was classified as a cystic adenocarcinoma of the kidney, originating from the proximal tubules.

Received October 7, 2016; accepted June 18, 2017 Published online July 31, 2017     

Chromatophoroma in a crevice kelpfish (Gibbonsia montereyensis)

A captive adult crevice kelpfish, Gibbonsia montereyensis, developed a cutaneous mass, approximately 9 × 7 mm on the right side of the head in an area of nonscaled skin. Following surgical debulking, examination of both impression smears and histologic sections of the tumor revealed a predominant population of round to spindloid to polygonal cells with a moderate amount of lightly basophilic cytoplasm. The cytoplasm was filled with round, variably-sized reddish-brown granules that often obscured the nucleus. Nuclei were round to ovoid with coarsely granular chromatin. There was minimal anisocytosis and anisokaryosis. The cytoplasmic granules in histologic sections were weakly positive by the Fontana-Masson method, and staining was eliminated with melanin bleach. Immunohistochemical staining was strongly positive with a murine monoclonal antibody for melan A. As the specificity of melan A for melanophores is not clearly defined in nonmammalian species, the tumor was examined by transmission electron microscopy. Melanophores were not detected. Instead, neoplastic cells were filled with numerous intracytoplasmic organelles with triple-limiting membranes composed of concentric lamellae; these structures were most compatible with pterinosomes, which are the pigment-containing organelles of cells called xanthophores and erythrophores. As both of these organelles are ultrastructurally indistinguishable and as kelpfish skin is known to contain both xanthophores and erythrophores, a diagnosis of a mixed pigment cell tumor or chromatophoroma was made. As the tumor was grossly reddish-brown, the possibility of a neoplastic population of only erythrophores could not be excluded. Pigment cell tumors, arising from cells of the embryonic neural crest, are common in reptiles and bony fish.     

The pagetoid variant of urothelial carcinoma in situ of urinary bladder in a cow

A case of urothelial carcinoma in situ of urinary bladder is reported in a 10-year-old cow naturally grazing on bracken-infested land. The cow suffered from enzootic hematuria for more than 5 years. The presence of bovine papillomavirus type 2 (BPV-2) DNA sequences was detected by polymerase chain reaction. The carcinoma in situ was characterized by the presence of anaplastic cells with amphophilic cytoplasm and pleomorphic nuclei containing granular, irregularly dispersed chromatin. Focal areas within the tumor contained large isolated and/or clustered cells. These cells had pale acidophilic cytoplasm, large nuclei with single or multiple nucleoli, and well-defined borders resembling Paget's cells. Immunohistochemically, all malignant cells were negative for vimentin and S-100 and positive for cytokeratins. In addition, normal and neoplastic cells expressed fragile histidine triad (FHIT) protein; surprisingly, some pagetoid cells did not. FHIT, the tumor suppressor gene at 3p14.2, encodes a protein of 147 amino acids (16.8 kd) with diadenosine triphosphate hydrolase activity and is a common target of deletions in human cancers of epithelial origin. Antibody to laminin detected a continuous epithelial basement membrane, thus clearly showing that neoplastic changes were limited to urothelial cells without invading stromal tissue. To our knowledge, this is the first report of an unusual pattern of spread of urothelial carcinoma in situ in a cow.     

Gastric adenocarcinoma with ossification in a ferret (Mustela putorius furo)

A 6-year-old female ferret had a firm mass 2 cm in diameter in the pyloric region of the stomach. Histopathologically, the mass was composed of neoplastic proliferation of well-differentiated epithelial cells, showing tubular or glandular growth patterns. Osseous metaplastic foci were often found in the tumor. Tumor cells showed a positive reaction for immunohistochemistry against bone morphogenetic protein-6, an osteogenic factor. A diagnosis of gastric adenocarcinoma with ossification was made.     

Subcutaneous Soft Tissue Sarcoma with Rhabdoid Features in a Dog

A nine-year-old male beagle dog had a white spherical mass in the subcutis of the left lumbar region. Microscopically, spindle to oval cells diffusely proliferated in the fibrous and myxoid stroma. Many neoplastic cells showed rhabdoid features or vacuolated cytoplasm. Immunohistochemically, the neoplastic cells were positive for vimentin and S100 and partly positive for neuron-specific enolase and glial fibrillary acidic protein but were negative for von Willebrand factor, desmin and α-smooth muscle actin. Ultrastructurally, the neoplastic cells had abundant cytoplasmic processes and desmosome-like structures. Cytoplasmic inclusions of rhabdoid-featured cells in HE sections were composed of aggregates of intermediate filaments, and cytoplasmic vacuoles were identified as an invagination of cytoplasm. Although malignant peripheral nerve sheath tumor was suggested according to these results, the present case was diagnosed as a soft tissue sarcoma with rhabdoid features due to a lack of identification of the basal lamina under electron microscopy.     

Cutaneous lymphoma in a juvenile dog

Abstract: An 18-month-old male Doberman Pinscher was referred to the Veterinary Medical Teaching Hospital of the College of Veterinary Medicine for an erythemic nodular mass on the right forelimb. The mass was diagnosed as cutaneous lymphoma, based on cytologic examination of a mass aspirate and histopathology. Using immunohistochemistry the neoplastic cells were positive for CD3 but negative for CD79a, E-cadherin, and pancytokeratin, confirming their origin as T lymphocytes. No tumor recurrence was noted 18 months after surgery. To our knowledge, this is the first report of a solitary nodular form of cutaneous lymphoma in a young dog.