Feline cutaneous neuroendocrine carcinoma (Merkel cell tumour): clinical and pathological findings

A case of a feline Merkel cell tumour is described. An 8-year-old, female cat developed a round, alopecic, reddish mass on the nose. Wide excisional surgery was performed with cartilage resection. Histologically the mass was composed of solid islands of mostly basophilic densely packed cells with a scant cytoplasm, which was suggestive of a neuroendocrine origin. Results of immunohistochemical studies using antibodies against neurone-specific enolase, chromogranin, synaptophysin and pan-cytokeratin allowed classification of the lesion as a Merkel cell tumour. Ultrastructurally, dense core granules were identified in the cytoplasm. In a 2-year follow-up no relapses or metastases were observed. The clinical course recorded is in contrast with the malignant nature of a Merkel cell tumour recently described in a cat and of the human Merkel cell tumour, but is similar to the course of the canine Merkel cell tumour which is often benign. Early diagnosis along with the use of wide surgical excision might be considered an important factor in preventing relapse of this tumour.     

Canine hepatic neuroendocrine carcinoma: an immunohistochemical and electron microscopic study

Ten dogs with neuroendocrine carcinoma of the liver were selected for inclusion in the study. Clinical signs were anorexia (7), vomiting (5), polydipsia/polyuria (3), icterus (2), lethargy (2), weight loss (2), paresis (1), ataxia (1), weakness (1), collapse (1), and urinary tract infection (1). Hematologic and biochemical abnormalities included anemia (2/8), leukocytosis (4/8), high liver enzyme activity (serum alkaline phosphatase, 7/9; alanine transaminase, 7/9; aspartate transaminase, 8/9), and high total bilirubin (6/9). Grossly, the tumors were diffuse, involving all liver lobes in six dogs, and two dogs had various-sized nodules in addition to diffuse involvement. Histologically, there were eight tumors with solid or trabecular pattern (group A), one tumor with cords or rows of neoplastic cells (group B), and one tumor with multiple rosette-like structures (group C). Immunohistochemical studies revealed that all 10 neoplasms were positive for at least one of the endocrine markers used: neuron-specific enolase (NSE; 8/10), synaptophysin (5/10), and chromogranin-A (3/10). A panel of NSE, chromagranin-A, and synaptophysin detected 100% of the tumors in our series. Electron microscopy confirmed the diagnosis by the presence of intracytoplasmic neurosecretory granules in the two examined cases. Our results show that neuroendocrine markers commonly used in humans can be used for the diagnosis of hepatic neuroendocrine carcinoma in dogs, preferably a panel of synaptophysin, chromagranin-A, and NSE because chromogranin-A alone is not as useful in dogs as in humans.     

Light and electron microscopic comparisons of cutaneous fibromas in white-tailed and mule deer

Cutaneous fibromas of white-tailed deer (Odocoileus virginianus), when compared with normal skin of the same species, had a thinner basement membrane; thickened stratum spinosum with numerous melanocytes, desmosomes, polyribosomes, and tonofilaments; focal hyperplasia of the stratum granulosum containing numerous large, electron-dense keratohyalin granules with irregular borders and containing occasional cells with diffuse intranuclear virus particles; and a moderately thickened stratum corneum with (although rarely) small crystalline arrays of virus particles. Normal mule deer (Odocoileus hemionus) skin was structurally similar to that of the white-tailed deer. Mule deer fibromas were similar to those in white-tailed deer, except for diffuse thickening of the stratum granulosum (the cells of which contained large keratohyalin granules of various electron densities with occasional composite granules) and except for a markedly thickened stratum corneum that contained numerous intranuclear viral inclusions. In negatively stained homogenates of tumors from both deer species, viral particles resembled papillomaviruses.     

An electron microscopic study of viruses associated with canine gastroenteritis

An electron microscopic study was carried out on specimens of feces and intestinal contents from cases of canine gastroenteritis submitted to the Diagnostic Laboratory, New York State College of Veterinary Medicine, during 1979-1981. The majority of samples came from New York State and the Northeast with no marked shift in distribution over the three year period. Canine parvovirus was the major virus identified. In August and September 1980 there was an epidemic of canine gastroenteritis, with 247 samples received during this two month period alone, of which 48 percent were positive for canine parvovirus. Almost half of the total number of specimens examined were from dogs less than 6 months of age and well over 50 percent of these were parvovirus positive. In addition to canine parvovirus, three cases of coronavirus, two cases of rota-like virus and one case of astro-like virus were detected. Three dual infections with canine parvovirus and rota or astro-like virus were also confirmed. An unidentified virus-like particle with cubic symmetry was found in two specimens. The adoption of immunoelectron microscopy for the detection of canine parvovirus in March 1980 facilitated identification of this virus and greatly increased the sensitivity of the technique.     

Feline papillomavirus infection in a cat with Bowen-like disease and cutaneous squamous cell carcinoma

A cutaneous mass in the neck was excised in a 13-year-old cat. Histopathological examination of the resected tissue revealed a multicentric squamous cell carcinoma in situ resembling Bowen's disease of man. The tumor showed a multifocal transformation to an infiltrative squamous cell carcinoma. Histological and immunohistological findings excluded actinic keratosis and feline viral plaques and allowed a classification as an irregular non-hyperkeratotic type of multicentric squamous cell carcinoma in situ. As a possible causative agent feline papillomavirus type 2 was detected using nested PCR in formalin-fixed material.     

Identification of matrix metalloproteinases in canine cutaneous mast cell tumors

Presence of matrix metalloproteinases has been associated with tumor invasion and metastasis in human neoplasia. The presence of matrix metalloproteinase 2 and matrix metalloproteinase 9 was determined in canine mast cell tumor tissue and normal stromal tissue from 24 dogs with spontaneously occurring cutaneous mast cell tumors. Seventeen of the mast cell tumors were of histologic grade 2, and 7 were of histologic grade 3. Gelatin zymography and computer assisted densitometry image analysis were used to quantify matrix metalloproteinase concentration. Bands from canine tissues migrated in the same location as human proenzyme and active enzyme matrix metalloproteinase 2 and matrix metalloproteinase 9 standards. A semiquantitative value for each patient sample was obtained by comparing the optical assessment density of each unknown band to the optical density of the human standard. The presence of matrix metalloproteinase 2 and matrix metalloproteinase 9 in histologic grade 2 mast cell tumors and histologic grade 3 mast cell tumors was compared, as was presence of matrix metalloproteinases in tumor and stromal tissue. There was dramatically more proenzyme matrix metalloproteinase 9 activity in histologic grade 3 mast cell tumors when compared to grade 2 tumors (P = .03). There was also dramatically more active enzyme matrix metalloproteinase 2 and active enzyme matrix metalloproteinase 9 activity in tumor tissue compared to stromal tissue (P = .02, P < .0001). This study demonstrates that the proenzyme and active enzyme forms of matrix metalloproteinase 2 and matrix metalloproteinase 9 are present in canine mast cell tumors. This appears to be related to the degree of histologic malignancy, although histologic grade 1 tumors were not evaluated.     

Immunohistochemical detection of P-glycoprotein (PGP) and multidrug resistance-associated protein (MRP) in canine cutaneous mast cell tumors

Fifty-four canine cutaneous mast cell tumors were evaluated immunohistochemically for the expression of P-glycoprotein (PGP) and multidrug-resistance-associated protein (MRP). All tumors examined were graded according to the histological malignancy. ranging from grade I to III. The expression of PGP was confirmed in 15% (8/54) of whole, 33% (5/15) of grade I, 10% (3/31) of grade II, and 0% (0/8) of grade III tumors. The expression of MRP was found in 18% (10/54) of whole, 26% (4/15) of grade I, 19% (6/31) of grade II, and 0% (0/8) of grade III tumors. The cases positive to at least one of these 2 multidrug markers were 26%, 47%, 23% and 0% of whole and grade I to III tumors, respectively. These results indicate that at least 26% of canine cutaneous mast cell tumors express PGP and/or MRP and that these tumors may be resistant to several anti-cancer drugs.     

Treatment of canine mast cell tumors with CCNU (lomustine)

The efficacy and toxicity of CCNU (1-[2-chloroethyl]3-cyclohexyl-1-nitrosourea) were evaluated in 23 dogs with measurable mast cell tumors (MCT). Twenty-two dogs had cutaneous MCT and 1 dog had an intranasal MCT Nineteen (83%) dogs had biopsy of their original mass performed and 4 (17%) had aspiration cytology of masses. Of the 19 tumors histologically graded, 1 (5%) neoplasm was classified as grade I, 10 (53%) were grade II, and the remaining 8 (42%) were grade III. Dogs were treated with CCNU at a dosage of 90 mg/m2 body surface area every 3 weeks. Response could be evaluated in 19 dogs. Eight of the 19 dogs (42%) had a measurable response to CCNU. One dog had a durable complete response for 440 days. Seven dogs (37%) had a partial response for a median and mean duration of 77 days and 109 days, respectively (range, 21-254 days). Treatment with CCNU resulted in stable disease in 6 dogs (32%) for a median and mean duration of 78 days and 122 days, respectively (range, 42-347 days). The acute dose-limiting toxicity was neutropenia 7 days after administration of CCNU. The median and mean neutrophil counts 7 days after CCNU were 1,452 cells/microL and 1,683 cells/microL, respectively (n = 17). Other toxicoses were uncommon. CCNU should be considered an active agent in the treatment of MCT in dogs.     

Immunohistochemical and clinical evaluation of p53 in canine cutaneous mast cell tumors

One hundred twenty-six cutaneous mast cell tumors obtained by excisional biopsy from 106 dogs were evaluated using immunohistochemical staining for the presence of p53 protein. A standard avidin-biotin immunohistochemical protocol was used incorporating a polyclonal antibody of rabbit origin (CM-1) as the primary antibody. Histopathologic grading of tumors was performed on hemotoxylin and eosin-stained samples. There was a significant difference in the percentage of cells staining positive for p53 for the histopathologic grades (P = 0.0005). Grade III tumors had a significantly greater p53 content than did grade I or II tumors (P < 0.05). Clinical data obtained retrospectively was available for 54 dogs. Tumor recurred in 19 of 54 (35.2%) dogs. Twenty-nine dogs died by the end of the study; 9 of 29 (31.0%) died of mast cell tumor disease. Histopathologic grade showed a significant negative association with survival time. Both clinical stage and histopathologic grade showed a significant negative association with time to recurrence. The percentage of cells staining positive for p53 did not significantly improve the forward analysis. Immunohistochemical detection of p53 did not appear useful in characterizing the clinical association between cutaneous mast cell tumor cellular features and survival time or time to tumor recurrence in dogs.     

Collagen dysplasia (cutaneous asthenia) in a cat

Hereditary collagen dysplasias comprise a complex group of connective-tissue disorders that result in the reduced tensile strength of affected tissues. These processes are called cutaneous asthenia in the skin of dogs and cats. We report here the case of a crossbred male cat, aged 6 months, that presented with two skin wounds in the region of the right thorax and right iliac tuberosity. The skin of these regions and of the animal's dorsum was hyperextensible, smooth to the touch, and easily torn with minor trauma. Microscopic examination of skin samples revealed reduced dermal connective tissue consisting of shortened and fragmented collagen fibers. Normal fibers were intermingled with altered fibers. Ultrastructural changes in collagen fibers included disorientation of fibrils within the same bundle, marked spacing differences, and variation in the diameter of transverse sections. The fibrils maintained the transverse striations characteristic of normal collagen.     

Immunohistochemical characterization of a hepatic neuroendocrine carcinoma in a cat.

A hepatic mass was identified in a 5-year-old, female mixed-breed cat that died spontaneously after a clinical history of progressive emaciation, ptyalism, and persistent coryza. At necropsy, a 7-cm-diameter, yellow-brown, firm, multilobulated tumor was identified in the liver. Microscopically, the mass consisted of neoplastic cells arranged in small, closely packed nests within a thin fibrovascular stroma. These cells were of medium sized and polygonal, with fine argyrophilic cytoplasmic granules. Nuclei were predominantly round with finely stippled chromatin and indistinct nucleoli. Mitotic figures were numerous. Immunohistochemically, most of the neoplastic cells were immunoreactive for chromogranin A, neuron-specific enolase (NSE), and cytokeratin AE1/AE3 and weakly labeled for synaptophysin. The tumor was negative for glial fibrillary acidic protein (GFAP), vimentin, and cytokeratins 5, 6, 8, and 17. Vascular emboli and intrahepatic micrometastasis were also identified with chromogranin A. All these features were consistent with a hepatic neuroendocrine carcinoma and emphasized the importance of using a panel of antibodies to diagnose such rare tumors.     

Metastatic neuroendocrine carcinoma of aortic body origin in a cat

An 8‐year‐old, female spayed Domestic Shorthair cat was presented to the Auburn University Emergency and Critical Care service for evaluation of pleural effusion and a suspected intrathoracic mass. Computed tomography was performed which confirmed the presence of a large intrathoracic mass, likely heart‐based. Fine‐needle aspirates were obtained and a cytologic diagnosis of a neuroendocrine tumor was made. Treatment with toceranib phosphate was briefly attempted at home by the owners. The cat died at home approximately 6 weeks after diagnosis. Necropsy and subsequent histopathologic examination revealed a metastatic neuroendocrine carcinoma of aortic body origin. Aortic body tumors are extremely rare in cats and to the authors’ knowledge, a neuroendocrine carcinoma of aortic body origin with distant metastases has not yet been reported in a cat.     

Scanning electron microscopic study of the dentinal tubules in dog canine teeth

Dentin adhesive restorative techniques are regularly used in veterinary dentistry. Knowledge of the microanatomic structure and properties of dentin is essential to ensure success in restorative procedures. The aim of this study was to describe the density and diameter of dentinal tubules in dog canine teeth using recently described standardized scanning electron microscopy techniques. The results showed dentin of dog canine teeth to be more oval-shaped with a higher tubular density and slightly larger tubular diameters compared with human teeth. These features suggest dog canine teeth have less intertubular dentin compared with human teeth, which may theoretically result in lower resin-dentin shear bond strengths.     

Alkaline phosphatase reaction of canine mammary mixed tumours: a light and electron microscopic study

Alkaline phosphatase (ALK-P) reactions at the light and electron microscopic levels were performed on eight canine mammary mixed tumours. In the morphologically normal gland next to the tumours, the myoepithelial cells and the stromal tissues near the acinar basement membranes both showed a positive ALK-P reaction by light microscopy. At the electron microscopic level, those parts of the myoepithelial cell membrane that were in contact with other cells--myoepithelial or lumenal epithelial--showed an ALK-P-positive reaction, as did the adjacent stromal tissue. The characteristic tumour cells, at sites of early proliferation, were ALK-P-positive, while in the mucoid and chondroid areas of the mixed tumours they were largely ALK-P-negative by light microscopy. By electron microscopy, those neoplastic cells which were in contact with other cells typically showed a positive ALK-P reaction, while those cells which were in contact with mucoid or chondroid matrix were largely negative. Although the cytoplasmic filaments of the neoplastic cells were 10 nm thick, and those of normal myoepithelial cells were 6 to 8 nm thick, the observations reported provide further evidence for the view that the essential cells of the canine mammary mixed tumour are derived from myoepithelial cells.     

Blastocyst implantation in the domestic cat. Light and electron microscopic study]

Blastocyst implantation in the domestic cat A light and electronmicroscopic investigation Implantation in the cat begins 121/2 days post coitum and lasts to the 14th day. Several hours before implantation begins the extraembryonic trophoblast, in what could be considered a precontact or sensitization phase, shows fine structural evidence of secretory activity. The uterine epithelium at the same times gives evidence of being at first resorptive and, after a differentiation, of being secretory. Secretion also in the gland epithelium can be observed. The attachment of the embryo to the endometrium begins with an appositional phase. The trophoblast is now distinctly resorptive and forms with the uterine epithelium microvilli-free areas of contact lying between the openings of the uterine glands. Then follows an adhesion phase during which additional junctional complexes are formed between an actively proliferating trophoblast and the uterine epithelium which shows now symplasmic differentiation. Finally, in the intrusion phase the uterine epithelium completely disintegrates. In this manner the syncytiotrophoblast which differentiates from the cytotrophoblast invades the maternal tissues until it reaches the endothelium of the uterine blood vessels.     

Variation among pathologists in histologic grading of canine cutaneous mast cell tumors.

Ten veterinary pathologists at 1 veterinary institution independently assigned histologic grades to the same 60 canine cutaneous mast cell tumors (MCTs). There was significant variation among pathologists in grading the MCTs (P < 0.001). The probability of assigning a low grade was significantly higher for the pathologists in this study who use a published reference for histologic grading of canine cutaneous MCTs that allows subcutaneous MCTs or MCTs with mitotic figures to be included in the low-grade category (P < 0.0001 and P < 0.0001, respectively).     

Cellular proliferation in canine cutaneous mast cell tumors: associations with c-KIT and its role in prognostication

Canine cutaneous mast cell tumor (MCT) is a common neoplastic disease in dogs. Due to the prevalence of canine MCTs and the variable biologic behavior of this disease, accurate prognostication and a thorough understanding of MCT biology are critical for the treatment of this disease. The goals of this study were to evaluate and compare the utility of the proliferation markers Ki67, proliferating cell nuclear antigen (PCNA), and argyrophilic nucleolar organizing region (AgNOR) as independent prognostic markers for canine MCTs and to evaluate the use of these markers in combination, as each marker assesses different aspects of cellular proliferation. An additional goal of this study was to evaluate the associations between cellular proliferation and c-KIT mutations and between cellular proliferation and aberrant KIT protein localization in canine MCTs. Fifty-six MCTs treated with surgical excision alone were included in this study. Each MCT was evaluated for Ki67 expression, PCNA expression, and KIT protein localization using immunohistochemistry; for AgNOR counts using histochemical staining; and for the presence of internal tandem duplication c-KIT mutations using polymerase chain reaction amplification. In this study, increased Ki67 and AgNOR counts were both associated with significantly decreased survival. On the basis of these results, we recommend that the evaluation of cellular proliferation, including evaluations of both Ki67 expression and AgNORs, should be routinely used in the prognostication of canine MCTs. Additionally, the results of this study show that MCTs with aberrant KIT protein localization or internal tandem duplication c-KIT mutations are associated with increased cellular proliferation, further suggesting a role for c-KIT in the progression of canine MCTs.