Coccygeal chordoma in a dog.

A 4-cm diameter spherical mass was removed from the region of the second coccygeal vertebra of a 6-year-old female Doberman Pinscher dog. The mass had been present for 7 months and was described as multilobular and smooth. Histologically, the neoplasm consisted of small spindle-shaped cells surrounding lobules of large vacuolated polygonal cells. Mucin was present within most lobules. The large polygonal cells stained positively with antibodies against vimentin, cytokeratin, and S-100 protein. Although the spindle-shaped cells stained positively with antibodies against vimentin, they only occasionally contained cytokeratin. The histology and immunohistochemistry are consistent with that reported for chordoma. Although 4 chordomas have previously been reported in dogs, this is the first case in which immunohistochemistry has been used to support the histological diagnosis. Neither recurrence nor metastasis was reported 10 months after surgical excision.     

Invasive ductal carcinoma of the mammary gland in a mare

A 21-year-old thoroughbred mare had a 35 x 14 x 10 cm mass involving the mammary gland. Metastases were found in the kidneys, lungs, skeletal muscles, and regional lymph nodes. Histopathologic examination of the tumor revealed a ductal solid carcinoma with extensive intraductal and intralobular involvement and focal infiltration of the adjacent stroma. The intralobular neoplasms were divided into irregularly shaped islands and sheets of polygonal and spindle-shaped epithelial cells by thick or thin fibrous connective tissue bundles. The neoplastic cells had a small or moderate amount of cytoplasm that stained faintly with eosin and round or oval hyperchromatic nuclei. Immunohistochemically, the neoplastic cells were strongly positive for Lu-5, weakly positive for AE1/AE3, vimentin, and glial fibrillary acidic protein, and negative for cytokeratin 8, cytokeratin 14, alpha-smooth muscle actin, calponin, and S100. The neoplasm was diagnosed as an invasive ductal carcinoma of the mammary gland with multiple metastases.     

The expression of p63 and cytokeratin 5 in mixed tumors of the canine mammary gland provides new insights into the histogenesis of these neoplasms

Cytokeratin 5 and p63 have been described as basal and myoepithelial cell markers in human breast. Mixed tumors of the canine mammary gland have been associated with a myoepithelial origin. Cytokeratin 5 expression has not been evaluated in these tumors. We investigated the relation between cytokeratin 5 and p63 double-immunohistochemical expression in 23 mixed tumors of the canine mammary gland (10 benign mixed tumors and 13 carcinomas arising from benign mixed tumors) and their origin. Cytokeratin 5 and p63 co-expression was observed in myoepithelial cells of benign mixed tumors, as well as in squamous differentiation of carcinoma arising from benign mixed tumors. Though a few interstitial spindle cells of the mesenchymal components expressed both p63 and cytokeratin 5, the basal epithelial cells were labeled only by cytokeratin 5. The co-expression of p63 and cytokeratin 5 in myoepithelial cells and squamous differentiation suggest that, like in human breast, cytokeratin 5 can also be considered a myoepithelial- and squamous-cell differentiating marker in canine tumors. The presence of some interstitial spindle cells stained for p63 and cytokeratin 5 might be associated with a myoepithelial origin of the mesenchymal component of mixed tumors of the canine mammary gland. Moreover, contrary to p63, basal epithelial cells were labeled by cytokeratin 5, indicating that cytokeratin 5 may not represent an exclusive myoepithelial cell marker but also a basal epithelial cell marker in canine mixed tumors. According to these data, basal epithelial cells may be related to the origin of the epithelial component of mixed tumors of the canine mammary gland.     

Synovial sarcoma in an Ayrshire heifer

An 8-month-old Ayrshire heifer had a rapidly growing mass in the axillary region of the left thoracic limb. The mass surrounded the distal humerus and entrapped nerves of the brachial plexus, causing an abnormal gait. Histologically, the mass was composed of clusters and cords of round to polygonal cells with scattered, spindle-shaped cells. The neoplastic cells stained positively for vimentin and cytokeratin. No staining was found with S-100 protein, kappa and lambda light chains, or T-cell markers by immunohistochemistry. On electron microscopic evaluation, the cytoplasm of the neoplastic cells contained few organelles, principally rough and smooth endoplasmic reticulum and mitochondria. This synovial sarcoma has histologic and ultrastructural features characteristic of the poorly differentiated subtype of synovial sarcoma in the human classification system.     

Lipid-rich carcinoma of the mammary gland in a cat

A 1.5-year-old female, intact, clinically healthy cat presented for a subcutaneous mass of the ventral abdomen. Surgical excision and microscopic examination of the mass were performed. Histologically, this was a discrete, unencapsulated, multilobular, expansile mass, which compressed the surrounding normal mammary tissue. Lobules were composed of tubuloacinar structures formed by atypical round to polygonal cells, which contained foamy to microvacuolated cytoplasm and variably sized, intracytoplasmic, distinct vacuoles causing nuclear peripheralization. Neoplastic cells demonstrated intense and diffuse immunoreactivity for cytokeratin and lacked immunoreactivity for vimentin. The vacuolar contents stained positively with Oil RedO and negatively with periodic acid-Schiff and Alcian blue stains. Histomorphologic, histochemical, and immunohistochemial analysis support a diagnosis of lipid-rich mammary carcinoma. This is the first report of a cat with a lipid-rich variant of mammary carcinoma.     

Undifferentiated tumor in the ovary of a corn snake (Elaphe guttata guttata)

A 6-year-old intact female corn snake (Elaphe guttata guttata) was presented with a 3-week history of anorexia. Coelomic radiographs revealed a 9 x 4 cm soft tissue opacity suggestive of a right ovarian enlargement. The mass (9 x 5 x 4 cm) was surgically removed, and multiple smears from tissue sections were stained with Diff-Quik. Multiple tissue samples from the mass were collected and fixed in formalin. Cytologic specimens were moderately cellular and contained light pink amorphous background material. The cells were primarily spindle-shaped with moderate to marked anisocytosis and anisokaryosis. Cells sometimes were round to polygonal, and rarely were arranged in small clusters. Macrophages occasionally were observed. Histologic specimens consisted of a highly cellular mass composed of pleomorphic, spindle-shaped cells and, occasionally, round to polygonal cells arranged in irregular fascicles. The neoplastic cells were immunoreactive for cytokeratin (AE1/AE3), smooth muscle actin, and skeletal muscle actin, but did not stain for vimentin or desmin. On the basis of the morphologic and immunohistochemical results, a diagnosis of ovarian undifferentiated carcinoma was made. In this report, we describe the challenges of using immunohistochemistry to diagnose this uncommon type of tumor in reptiles.     

Orbital adenocarcinoma of lacrimal gland origin in a dog.

A 13-year-old intact female mixed-breed dog was presented for a progressive enlargement of the right eye, which had been treated previously for conjunctivitis. A round, firm mass, approximately 4 cm in diameter, was protruding from the superotemporal aspect of the right orbit, displacing the eyeball anteriorly and ventromedially. The mass was encapsulated, distinct from the eyeball, and not associated with the eyelids. On cut surface, there was a pale multilobulated periphery, with a dark red, soft, and depressed core. Histologically, tumor cells formed cords and tubules, which were stained with mouse anti-human cytokeratin antibody AE1/AE3. Residual glands were serous, and the majority of tumor cells were negative for mucin. The supraorbital location, encapsulation, and residual serous glands suggest that this mass was a low-grade adenocarcinoma of the lacrimal gland.     

Calponin expression and myoepithelial cell differentiation in canine, feline and human mammary simple carcinomas

Calponin is a 34‐kDa smooth muscle‐specific protein that has been shown to be a highly sensitive marker of myoepithelial cells in canine, feline and human mammary tissue and tumours. The expression of calponin was studied in 15 canine, 32 feline and 28 human simple mammary carcinomas using a monoclonal mouse antihuman calponin antibody and the avidin–biotin peroxidase complex (ABC) immunohistochemical technique. Calponin expression was compared with the expression of cytokeratin 14, a marker of normal mammary myoepithelial cells in the three species. Four different types of calponin‐positive cells were identified: (1) Type 1: cytokeratin‐14‐positive pre‐existing myoepithelial cells forming a continuous layer with images of focal disruptions; (2) Type 2: cytokeratin‐14‐positive isolated nests of fusiform, polygonal or round cells without atypia; (3) Type 3: cytokeratin‐14‐positive atypical cells indistinguishable from non‐reactive atypical cells, which should have never been detected in haematoxylin and eosin‐stained sections and (4) Type 4: cytokeratin‐14‐negative stromal fusiform cells around the neoplastic growth or cell nests, identified as myofibroblasts. Calponin‐negative and cytokeratin‐14‐positive atypical neoplastic cells were observed in three canine, 28 feline and two human carcinomas. The latter were indicative of altered expression of high‐molecular‐weight cytokeratins in luminal epithelial‐type simple carcinomas. Our findings show that calponin is a good marker of myoepithelial cell differentiation in feline, human and, particularly, canine simple carcinomas. The high number (six out of 15) of canine tumours with type 3 cells points to the need of both introducing calponin examination in the routine diagnostic schedule and performing further studies on its prognostic significance.     

Cytologic, histologic, and immunohistochemical features of lingual liposarcoma in a dog

A 9-year-old female spayed mixed-breed dog was presented to the referring veterinarian with a history of decreased appetite and difficulty with prehension and swallowing because of a firm oval mass in the tongue. On cytologic evaluation of a fine-needle aspirate of the mass there were numerous round to polygonal cells organized individually or in loose clusters with rare branching capillaries. The cells had eosinophilic granular cytoplasm, round to oval nuclei, and occasionally indistinct borders. The cytologic diagnosis was granular cell tumor (GCT) of the tongue. Impression smears of a biopsy sample of the lingual mass contained similar eosinophilic granular cells with variable numbers of clear vacuoles in the background, numerous perivascular arrangements, and occasional lipoblasts, suggestive of liposarcoma. On histologic examination the tumor was composed of numerous lipocytes with rare foci of round eosinophilic granular cells without evidence of vacuolation; occasionally, atypical mitotic figures were seen. Immunohistochemically, the cells were uniformly negative for periodic acid-Schiff and did not express smooth muscle actin, desmin, or cytokeratin but were immunoreactive for vimentin and S100. A diagnosis of well-differentiated liposarcoma was made on the basis of morphologic and immunohistochemical results. Eosinophilic granular cells may be a component of well-differentiated liposarcoma and are not limited to GCT. Liposarcoma should be considered in the differential diagnoses of lingual tumors in the dog when cytological evaluation reveals eosinophilic granular cells consistent with GCT.     

The expression of intermediate filaments in canine mammary glands and their tumors

Monoclonal antibodies specific for different types of intermediate filaments (cytokeratin, vimentin, desmin and neurofilaments) were used to study the histogenesis of canine mammary glands and 57 canine mammary tumors by immunocytochemistry. The intra- and interlobular duct epithelium, acinar, and intralobular myoepithelial cells stained positively for cytokeratin. Peripheral ductal and acinar cells, as well as interstitial cells, stained positively for vimentin. A similar staining pattern was seen in adenomas, complex adenomas, benign mixed tumors, ductular carcinomas, and one myoepithelioma-like tumor. Additionally, cytokeratin positive cells were scattered interstitially in one single adenoma, most complex adenomas, some benign mixed tumors, complex carcinomas, and in the malignant mixed tumors. All stromal cells stained positively for vimentin. The fibrosarcomas were positive only for vimentin, while the following expressed both desmin and cytokeratin: epithelial-like cells in one adenoma, three complex adenomas, the myoepithelioma-like tumor, the single comedo carcinoma, two complex carcinomas, the single lobular carcinoma, one malignant mixed tumor, and three osteosarcomas. Epithelial-like cells in one adenoma, six complex adenomas, two benign mixed tumors, two complex carcinomas, the lobular carcinoma, and the malignant schwannoma stained for neurofilaments. Three tumors, one adenoma, one complex adenoma, and the lobular carcinoma expressed both desmin and neurofilaments in addition to cytokeratin and vimentin. The results show the expression of different types of intermediate filaments and indicate that there might be a stem cell origin in most of the canine mammary tumors.     

Immunohistochemical evaluation of a malignant intestinal carcinoid in a dog

An intestinal carcinoid with multiple metastases was identified in a 5-year-old male Shih Tzu with a clinical history of anemia, fatigue, anorexia, vomiting, intermittent diarrhea, intestinal bleeding, and progressive emaciation. There was a yellowish-white mass 15 mm in diameter in the anterior jejunum and white nodules consistent with metastases in many organs. Histopathologically, the mass consisted of neoplastic cells arranged in lobules, trabeculae, or closely interdigitating islands of cells. Neoplastic cells were generally polygonal with round hyperchromatic nuclei, modest amounts of eosinophilic cytoplasm, and eosinophilic cytoplasmic granules. Mitoses were common. Rosette formations of tumor cells were apparent in metastatic tumors. Immunohistochemically, tumor cells stained positive for cytokeratin 13, synaptophysin, protein gene product 9.5, neuron-specific enolase, chromogranin A, calcitonin gene-related peptide, serotonin (5-HT), and Leu-7. Serum 5-HT concentrations for this dog were increased 10-fold compared with those of normal dogs. All findings were consistent with a diagnosis of a malignant intestinal carcinoid.     

A spontaneous thymic carcinosarcoma in a young Sprague Dawley rat

We encountered a case of spontaneous thymic carcinosarcoma in a young Crl:CD (Sprague Dawley) rat. Grossly, a white multinodular mass replaced the thymus in the thoracic cavity. Histologically, multiple nodules were separated by fibrous stroma, and each nodule included isolated regions that were composed of epithelial or non-epithelial tumor cells. The epithelial tumor cells were relatively large and round to polygonal cells with large nuclei and weakly eosinophilic cytoplasm. These cells were cytokeratin-positive and vimentin-negative. These cells infiltrated the lungs. The non-epithelial tumor cells were poorly differentiated, small, round to spindle-shaped cells with small nuclei and basophilic cytoplasm. These cells were vimentin-positive and mostly cytokeratin-negative. Many islands of cartilage were observed near non-epithelial cells. Based on these findings, the tumor was diagnosed as a primary thymic carcinosarcoma consisting of a malignant thymoma composed of epithelial tumor cells and a mesenchymal chondrosarcoma composed of non-epithelial tumor cells.     

Metastatic balloon cell melanoma in a dog

Background: Balloon cell melanoma is a rare variant of amelanotic melanoma that is difficult to differentiate from sebaceous cell carcinoma, liposarcoma, and other clear cell neoplasms without immunohistochemistry or ultrastructural evidence of melanin or melanosomes. Objective: The purpose of this report was to describe the clinical, cytologic, histologic, immunohistochemical, and ultrastructural findings in a dog with metastatic balloon cell melanoma. Methods: A 6‐year‐old female Golden Retriever was evaluated for a white, flocculent infiltrate in the anterior chamber of the left eye and an enlarged left prescapular lymph node. Cytologic evaluation of the eye and lymph node were performed following aqueocentesis and fine‐needle aspiration, respectively. The affected lymph node was examined histologically and stained for cytokeratin, vimentin, S‐100, and Melan A. Following euthanasia a necropsy was performed and samples of the affected lymph node were examined by electron microscopy. Results: Cytologic examination of the lymph node and aqueocentesis sample revealed round neoplastic cells that had abundant clear vacuolated cytoplasm. A tentative diagnosis of metastatic sebaceous cell carcinoma or clear cell neoplasm was made. Histologically, the affected lymph node had similar polygonal clear cells arranged in sheets and packets divided by delicate fibrovascular stroma. Immunohistochemical staining of the cells was negative for cytokeratin but positive for vimentin, weakly positive for S‐100, and strongly positive for Melan A. At necropsy, metastatic lesions were identified in the diaphragm, heart, lung, kidneys, left eye, prescapular and sublumbar lymph nodes, and multiple skin sites. Ultrastructural examination of neoplastic lymph nodes revealed many membrane‐bound vacuoles, myelinlike figures, and rare melanosomes. Conclusion: Immunohistochemical staining and ultrastructural features of the neoplastic cells supported a diagnosis of metastatic balloon cell melanoma.     

Immunohistochemical demonstration of keratin in canine neuroepithelioma

Morphological features and immunoreactivity for cytokeratin (CK), glial fibrillary acidic protein (GFAP) and neuron-specific enolase (NSE) of three canine neuroepitheliomas and three canine ependymomas were investigated. Neuroepitheliomas were in three German shepherds as intradural-extramedullary solitary masses, with spinal cord displacement between T10 and L2. Histologically, they contained tubules and acini, lined by epithelial cells with focal squamous metaplasia, rosette-like structures, and polygonal to spindle-shaped cells between tubules. Acini were empty or filled with a homogeneous, eosinophilic periodic acid-Schiff (PAS)-positive material. Mitotic indices varied from low to moderate. Ependymomas occurred in the third (two cases) and fourth ventricle in adult boxers. Histologically, they were composed of cells with an ill-defined, scant amphophilic cytoplasm, with a central round euchromatic nucleus; cells formed pseudorosettes, with a central fibro-vascular stroma. Neuroepitheliomas stained for CK, but ependymomas did not. Both failed to stain for GFAP, NSE, or phosphotungstic acid hematoxylin (PTAH). Thus, antibodies to cytokeratin are useful to distinguish neuroepitheliomas from ependymomas.     

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.     

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.     

Dermal intravascular leiomyosarcoma in a cat

A 10-year-old female spayed domestic shorthaired cat presented with a subcutaneous tumor between the first and second phalanges of the left hind foot. Six months after excision, a similar tumor occurred on the medial aspect of the third phalanx of the same limb. Histologically, both tumors consisted of solid masses of spindle and round cells, many of which grew within endothelial-lined vessels. Tumor cells stained positively for smooth muscle actin and vimentin, but were negative for cytokeratin, S-100, desmin, synaptophysin, factor VIII-related antigen, and neuron-specific enolase. The diagnosis was dermal intravascular leiomyosarcoma.     

Well-differentiated biphasic synovial sarcoma in the atlanto-occipital joint of a Holstein cow

A 7-year-old Holstein cow developed a large cystic mass in the region between the atlantoaxis and larynx. The mass extended to the synovium in the atlanto-occipital joint. Many villous projections were present on the inner surface of the tumor tissue, and irregular clefts were formed in the inside. Two cell types, epithelioid-like synovioblasts and spindle cells, were present. Immunohistochemical analysis showed that the cells stained positively for cytokeratin (AE1/AE3) and vimentin. Both cells had similar fine structures ultra-structurally. Vacuoles present in the cytoplasm were full of an acid mucous substance. The tumor was diagnosed as a well-differentiated biphasic synovial sarcoma. This is the first report of a rare case of synovial sarcoma, from the viewpoint of its origin.     

Malignant mixed mullerian tumor in a rabbit (Oryctolagus cuniculus): case report with immunohistochemistry

A rabbit (Oryctolagus cuniculus) with a homologous malignant mixed müllerian tumor (MMMT) of the uterus with decidualization in the sarcomatous components is described. On histologic examination, the neoplasm was characterized by a carcinomatous and a sarcomatous component with invasion of the myometrium. The epithelial component was a well-differentiated carcinoma, and the nonepithelial component contained large amounts of intracytoplasmic glycogen. The changes in stromal cells were morphologically similar to changes usually found in decidual cells in the pregnant uterus or in deciduosarcomas in rabbits. Results of immunohistochemical analysis indicated that the epithelial components stained positive with cytokeratin (CK7, AE1/3) and the decidual-stromal cells stained positive for vimentin, but did not stain with alpha-SMA, actin, and desmin. This case fulfills all the criteria of an MMMT in having a carcinomatous and a sarcomatous component, but differs from cases of MMMT in women in that the sarcomatous component had decidualized. To the authors' knowledge, this is the first report of a malignant mixed müllerian tumor in rabbits.     

Cutaneous melanoma in a ferret (Mustela putorius furo)

A 4-year-old spayed female ferret (Mustela putorius furo) was clinically evaluated for a slightly raised subcutaneous mass in the dorsal lumbar area. The mass was surgically excised and submitted for histopathologic evaluation. Histologically, the mass was composed of closely packeted large, atypical, polygonal to spindle-shaped cells arranged in sheets and short bundles. A few cells contained variable amounts of granular, brown to black intracytoplasmic pigment. Warthin-Starry and Fontana-Masson silver stains demonstrated variable numbers of fine black intracytoplasmic granules in most cells. The atypical cells stained positively for vimentin and S100 protein and negatively for cytokeratin and Melan A. Ultrastructurally, the neoplastic cells contained intracytoplasmic melanosomes in different stages of development. Compound melanosomes were not identified. To our knowledge, this report documents the first case of a spontaneous cutaneous melanoma in the ferret.