Paratracheal cervical mass in a dog

A 14-year-old female Welsh Terrier was presented for evaluation of multiple skin masses. Two of them were diagnosed as a follicular (epidermal) cyst and a sebaceous epithelioma by cytology and histopathology. The third mass was located in the subcutis adjacent to the cervical trachea. Clinical findings, thoracic radiography, and laboratory results were otherwise unremarkable. Cytologically, the cervical mass was characterized by the presence of round to polygonal cells with distinct cell borders, mild to moderate anisocytosis, round to oval eccentric nuclei with prominent nucleoli, and a variable amount of finely granular, eosinophilic cytoplasm. Differential diagnoses included endocrine/neuroendocrine tumors such as thyroid adenocarcinoma, medullary thyroid carcinoma, carotid body chemodectoma, and parathyroid carcinoma. The mass was removed surgically and submitted for histopathologic and immunohistochemical examination. Histologically, the mass was composed of rows and nests of densely packed cells separated by thin fibrovascular stroma. Neoplastic cells had moderate to large amounts of pale eosinophilic dusty or finely vacuolated cytoplasm and round to oval nuclei with finely dispersed chromatin and 1 or 2 small nucleoli. On immunohistochemistry, neoplastic cells were positive for chromogranin A, calcitonin, and neuron-specific enolase, and were negative for cytokeratin and thyroglobulin. The final diagnosis was medullary thyroid carcinoma, an uncommon endocrine tumor of dogs that has cytologic and histopathologic features similar to other endocrine and neuroendocrine tumors. Immunohistochemistry or immunocytochemistry should be performed to differentiate medullary thyroid carcinoma from other endocrine/neuroendocrine tumors of dogs.     

Metastatic pancreatic polypeptide‐secreting islet cell tumor in a dog

Abstract: A 14‐year‐old female spayed Golden Retriever was presented to the University of Florida's Veterinary Medical Center with history of lymphoplasmacytic gastroenteritis, intermittent vomiting, watery diarrhea, and weight loss for over a year. CBC, biochemical profile, and urinalysis were within reference intervals. Abdominal ultrasonographic examination revealed mesenteric and jejunal lymphadenopathy and hyperechoic hepatic nodules. Cytologic examination of the enlarged lymph nodes revealed loosely cohesive cells with moderate nuclear pleomorphism and rare punctate eosinophilic cytoplasmic granules. The cytologic interpretation was metastatic neuroendocrine neoplasia. On surgical exploration, a mass was detected in the right lobe of the pancreas. Histologic evaluation determined the mass to be an islet cell tumor. Approximately 98% of cells were positive by immunolabeling for pancreatic polypeptide (PP), and only rare cells were positive for insulin or somatostatin. All cells were negative for glucagon, gastrin, vasoactive intestinal polypeptide, protein gene product 9.5, synaptophysin, and chromogranins A and B. Pancreatic tumors that primarily produce PP are rare in dogs, and this is the first report of both the cytologic and histologic features of an islet cell tumor predominantly secreting PP. Clinical signs for these tumors are typically absent or nonspecific; signs may include watery diarrhea, as noted in this dog, although the diarrhea may have resulted from lymphoplasmacytic gastroenteritis. Additional case studies are needed to further characterize the cytomorphologic features and clinical presentation of PP‐secreting islet cell tumor, or polypeptidoma, in dogs.     

Epididymal interstitial (Leydig) cell tumors in B6C3F1 mice

Six primary interstitial cell tumors of the epididymis were identified from 46,752 male B6C3F1 mice used in chronic toxicity and carcinogenicity studies. Five of the tumors occurred at the end of 2-year studies; none were attributed to treatment. None of the mice with epididymal tumors had a primary testicular tumor. Histologically, tumors were characterized by a nodular or diffuse proliferation of tumor cells in the epididymal interstitium. Most cells were polygonal with highly vacuolated cytoplasm (vacuolated cells) or eosinophilic cytoplasm (eosinophilic cells). Smaller hyperchromatic cells with scant basophilic cytoplasm (basophilic cells) and cells with yellow-brown pigment characteristic of lipofuscin (pigmented cells) were less common. In each tumor two or more cell types were present. Extension of these tumors through the capsule, invasion of the testis, or metastasis did not occur. By electron microscopy both eosinophilic and vacuolated cell types had a large round or oval nucleus with sparse heterochromatin, abundant mitochondria with tubulovesicular cristae, and frequent desmosome structures between cell membranes. Vacuolated cells contained numerous lipid droplets. Morphological features of the epididymal tumors are similar to those of the testicular interstitial (Leydig) cell tumor in mice and rats.     

Diagnostic use of cytologic examination of bone marrow from dogs with thrombocytopenia: 58 cases (1994-2004)

OBJECTIVE: To determine the diagnostic use of cytologic examination of bone marrow from dogs with thrombocytopenia. DESIGN: Retrospective case series. ANIMALS: 58 dogs with thrombocytopenia. PROCEDURES: Medical records were searched and reviewed for dogs with thrombocytopenia. Dogs that had thrombocytopenia and cytologic examination of bone marrow were included in the study. Dogs with other hematologic abnormalities, with a previous diagnosis of hematopoietic neoplasia, or that had previous treatment with cytotoxic drugs were excluded. Bone marrow cytologic findings were reviewed. Results were compared between dogs with severe thrombocytopenia (< 20,000 platelets/microL) and dogs with mild to moderate thrombocytopenia (20,000 to 200,000 platelets/microL). RESULTS: 58 dogs met the inclusion criteria. Of 55 dogs with diagnostic bone marrow aspirates, 36 had severe thrombocytopenia. Cytologic evaluation of bone marrow did not reveal substantial nonmegakaryocytic bone marrow abnormalities or result in a definitive diagnosis in any of these dogs. Nineteen dogs with mild to moderate thrombocytopenia had diagnostic bone marrow aspirates. Bone marrow cytologic findings revealed nonmegakaryocytic abnormalities in 4 of these dogs. Significantly fewer dogs with severe thrombocytopenia had abnormalities identified on cytologic examination of bone marrow, compared with dogs with mild to moderate thrombocytopenia. CONCLUSIONS AND CLINICAL RELEVANCE: Cytologic examination of bone marrow is unlikely to provide specific diagnostic or prognostic information in dogs with severe thrombocytopenia.     

Cytologic,histologic, and immunohistochemical features of maxillofacial alveolar rhabdomyosarcoma in a juvenile dog

Abstract: A 15‐month‐old castrated male dog with a history of intermittent epistaxis and sneezing was admitted for the examination of a maxillofacial mass. An impression smear of a biopsy sample from the cauliflower‐shaped gingival mass contained numerous round cells, 5–25 μm in diameter, which contained a moderate amount of clear to pale blue cytoplasm and resembled lymphoid cells. Mitotic figures were frequently observed. The mass was diagnosed as malignant round cell neoplasia. On histologic examination the tumor was composed of diffusely arranged, small, atypical round cells with a small amount of fibrovascular stroma. Immunohistochemically, the cells were negative for CD3, CD18, CD20, CD79α, cytokeratin, melan‐A, chromogranin A, α‐smooth muscle actin, and myoglobin but positive for vimentin and desmin. The cells also had strong positive nuclear staining for myogenin and MyoD1. A diagnosis of solid‐pattern alveolar rhabdomyosarcoma was made on the basis of morphologic and immunohistochemical results. Alveolar rhabdomyosarcoma should be considered in the differential diagnosis of tumors in juvenile dogs, especially when cytologic findings reveal round, undifferentiated cells.     

Sensitivity and specificity of cytologic evaluation in the diagnosis of neoplasia in body fluids from dogs and cats

Sensitivity and specificity were determined for the cytologic detection of malignant tumors in canine and feline body cavity effusions. In a prospective study, 424 body cavity effusions from dogs and cats were collected and evaluated, including 70 pleural and 163 peritoneal effusions from dogs, and 77 pleural and 114 peritoneal effusions from cats. Final diagnoses were confirmed in 339 of the 424 cases by clinical follow-up, necropsy, and in the case of malignant tumors, Histopathology. Malignant tumors were found in 18% of canine and 25% of feline body cavity effusions. Approximately one-half of tumors in both dogs and cats were carcinomas. Discrete cell tumors accounted for 56% of feline neoplastic effusions. The sensitivity of cytologic evaluation for the detection of malignant tumors in body cavity effusions was 64% for dogs and 61% for cats. Specificity was 99% for canine and 100% for feline effusions. Sensitivity and specificity were comparable to those obtained with cytologic evaluation of human samples.     

Immunocytochemical differentiation of canine mesenchymal tumors in cytologic imprint preparations

BACKGROUND: Immunocytochemical techniques are a potentially valuable diagnostic tool to support cytologic diagnosis in dogs. However, detailed studies of staining patterns and intensity in cytologic specimens of mesenchymal tumor types are lacking. OBJECTIVE: The aim of this study was to evaluate commercially available antibodies against human proteins for use in the characterization of canine tumors of mesenchymal origin in cytologic samples. METHODS: Immunocytochemical staining was performed on air-dried imprint specimens of biopsies obtained from 103 mesenchymal neoplasms and 14 metastatic lesions from 98 dogs. All specimens were stained with anti-cytokeratin AE1/AE3 and vimentin. Based on the histologic diagnosis, tumors of muscle, endothelial, histiocytic, and melanocytic origin also were stained with cell-specific antibodies. Staining intensity was subjectively graded and the percentage of positive tumor cells was estimated. RESULTS: All mesenchymal tumors and metastases, with the exception of mesotheliomas, were vimentin-positive and cytokeratin-negative; mesotheliomas (n=6) were positive for both vimentin and cytokeratin. Tumors of muscle (n=5), endothelial (n=15), and histiocytic (n=18) origin stained moderately to strongly positive in a majority of tumor cells with desmin, von Willebrand factor, and lysozyme, respectively. Malignant melanomas (n=15) had variable staining and a variable percentage of positive cells with Melan-A and S100. CONCLUSIONS: Our results indicate that immunocytochemical staining of canine cytologic specimens is a reliable and sensitive technique that may be of benefit for the differentiation of poorly differentiated mesenchymal tumors and metastases. Additional study is needed to assess the specificity of immunocytochemical stains in mesenchymal tumors.     

Mixed germ cell tumor in the eye of a dog.

A 3-year-old female neutered Staffordshire Bull Terrier presented with a mixed germ cell tumor involving the base of the iris and the ciliary body of the right eye. The tumor mass was composed primarily of packeted vacuolated, polygonal (hepatoid) cells and small round cells; epithelial cells lining tubuloacinar structures were a less prominent component. The hepatoid and round cells stained positively for alpha-fetoprotein and cytokeratin. The epithelial cells stained positively for cytokeratin only, and some contained cytoplasmic mucin droplets. The polygonal cells were interpreted as a hepatoid variant of yolk sac tumor, and the epithelial cells were considered a teratomatous component. Trabeculae of bone were observed within the mass and may have been metaplastic or a teratomatous element. Extragonadal germ cell tumors are rare in dogs and have previously been reported only in the suprasellar region. This is the first report of this tumor type in the eye of a nonhuman species.     

Diagnostic value of cytologic examination of gastrointestinal tract tumors in dogs and cats: 83 cases (2001-2004)

OBJECTIVE: To determine results of cytologic examination of fine-needle aspirates and impression smears of gastrointestinal tract tumors in dogs and cats. DESIGN: Retrospective case series. ANIMALS: 38 dogs and 44 cats with histologically confirmed gastrointestinal tract tumors. PROCEDURES: Results of cytologic examination of fine-needle aspirates (n = 67) or impression smears (31) were compared with the histologic diagnosis, and extent of agreement was classified as complete, partial, none, or undetermined. RESULTS: For 48 of the 67 (72%) fine-needle aspirates, there was complete or partial agreement between the cytologic and histologic diagnoses. For 12 (18%) aspirates, the extent of agreement could not be determined because the cytologic specimen was considered unsatisfactory. For 29 of the 31 (94%) impression smears, there was complete agreement between the cytologic and histologic diagnoses, and for 2 (6%), there was partial agreement. None of the impression smears were considered unsatisfactory. Proportion of samples with complete agreement and proportion of samples with complete or partial agreement were significantly higher for impression smears than for fine-needle aspirates. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that there was moderate agreement between results of cytologic examination of fine-needle aspirates from dogs and cats with gastrointestinal tract neoplasia and the definitive histologic diagnosis. The agreement between results of cytologic examination of impression smears and the histologic diagnosis appeared to be higher.     

Histopathological and immunohistochemical characteristics of two canine lipid-rich mammary carcinomas

Clinicopathological and immunohistochemical findings of two uncommon canine lipid-rich mammary carcinomas are described. The predominant histological feature in both tumours was the presence of at least 80% of cells with intracytoplasmic vacuoles which stained positively with Sudan IV but not with alcian-blue periodic acid-schiff method. In both tumours, small groups of non-vacuolated cells were identified among the vacuolated cells. However, histological and immunohistochemical differences were also found between these tumours. Thus, one of them was composed of tumour cells with a large and single vacuole, which were arranged in lobular pattern, while the other neoplasm showed an intraductal growth of tumour cells with a fine vacuolated cytoplasm. Immunohistochemically, in the first tumour most vacuolated cells were positive for CK (cytokeratin)8-7, indicating a secretory epithelial immunophenotype while CK5 and CK8-7-expressing non-vacuolated cells were associated with luminal duct immunophenotype. However, in the second tumour the expression of CK14 in most of vacuolated cells and alpha-smooth muscle actin (alpha-SMA) in non-vacuolated cells, alone or in combination with CK5 suggested a myoepithelial immunophenotype for both cell types. These results suggest heterogeneity of the cell type and growth pattern for this type of canine tumour as has been described in women but not in dogs.     

Lipid-rich carcinomas of the mammary gland in seven dogs: clinicopathologic and immunohistochemical features

Lipid-rich carcinomas occurred in seven female dogs. Affected dogs were purebred (all but one), intact (all but one), and between 4 and 13 years of age. Five of them had a history of parity, one had pseudopregnancy, and none had received contraceptive steroids. The tumors were single (five cases) or multiple (two cases) well-circumscribed masses of different sizes (varying from 1 to 6 cm in diameter), composed of solid nests and cords of tumor cells separated by a moderate amount of stroma. The tumor cells contained either multiple and small or large and solitary vacuoles that pushed the nucleus to the periphery of the cell (signet-ring cell). A glandular epithelial immunophenotype (cytokeratins 5 and 8 and 8 and 18) was observed in the majority of tumor cells. All tumors lacked both estrogen and progesterone receptors, and five out of seven tumors gave rise to local recurrence and proximal or distant metastases or both.     

Morphologic characterization of specific granules in Greyhound eosinophils

BACKGROUND: "Vacuolated" eosinophils (ie, eosinophils with empty, nonstaining granules) have been described previously in normal Greyhounds. However, to our knowledge, detailed studies of granules in vacuolated and normal eosinophils in this breed have not been performed. OBJECTIVE: The objective of this prospective study was to characterize some of the morphologic, ultrastructural, and cytochemical staining features of specific (primary) granules in both normal and vacuolated eosinophils in Greyhound blood. METHODS: Morphologic features of eosinophils in Wright's- and Diff-Quik-stained peripheral blood smears from 49 Greyhounds were compared with 200 blood smears from non-Greyhound dogs. Transmission electron microscopy was done on blood from 3 Greyhounds with vacuolated eosinophils and 3 with normal eosinophil granules. Blood smears from 4 of these dogs also were stained cytochemically with alkaline phosphatase (AP), chloracetate esterase (CAE), and alpha naphthyl butyrate esterase (ANBE). The morphologic features and tinctorial properties of vacuolated and normal eosinophils were compared. RESULTS: Twenty-six Greyhounds (53%) had vacuolated eosinophils and 23 (47%) had normal granulated eosinophils in smears stained with Wright's stain. Only 1% of eosinophils were vacuolated in non-Greyhound dogs. Twenty of the 23 (85%) Greyhounds with normal granulated eosinophils on Wright's-stained smears had vacuolated eosinophils in smears stained with Diff-Quik. Ultrastructurally, no morphologic differences were observed between granules of vacuolated and normal eosinophils. Both vacuolated and normal eosinophils in Greyhounds were positive for AP and negative for CAE and ANBE, as expected for normal dogs. CONCLUSION: Vacuolated eosinophils in Greyhounds likely reflect, at least in part, differential staining properties of the specific granules with different hematologic stains. Ultrastuctural and cytochemical features of eosinophil granules were similar in normal and vacuolated eosinophils from Greyhounds.     

Basal cell tumor or cutaneous basilar epithelial neoplasm? Rethinking the cytologic diagnosis of basal cell tumors

A 1-cm-diameter, red, raised, cutaneous mass over the dorsal surface of the left third metacarpal of a 6-year-old neutered male yellow Labrador Retriever was aspirated. The aspirate contained cohesive clusters of cells, some containing cells with increased pleomorphism. Cellular debris (some keratinized), melanin, large numbers of macrophages, a few neutrophils, and fibroblasts were also observed. The cytologic interpretation was malignant neoplasia with histiocytic inflammation. Differentials included a carcinoma or, given the melanin pigment and variable morphology of the cells, possibly malignant melanoma. Histologically, the tumor was diagnosed as a basal cell epithelioma. Neoplasms that once were lumped into the broad histologic diagnosis of basal cell tumors have since been split into distinct entities, dependent on evidence of differentiation into epidermis, trichofollicular epithelium, or sweat or sebaceous glands. Although histologic reclassification has resulted in removal of most of these entities from the original basal cell tumor category, a cytologic diagnosis of basal cell tumor continues to be used to represent the large, heterogeneous group of epidermal, trichofollicular, and adnexal skin tumors with basal cell characteristics. The case in this report demonstrates the heterogeneity of neoplasms that may be diagnosed cytologically as basal cell tumors and supports the need for cytologic criteria and nomenclature that better reflect potential variation in tissue differentiation.     

Canine angiosarcoma: cytologic, histologic, and immunohistochemical correlations

BACKGROUND: Angiosarcomas (AS) are malignant tumors that arise from vascular endothelial cells and are common in dogs. Histologically, AS are markedly heterogeneous neoplasms that make interpretation by cytology difficult. OBJECTIVE: Our objective was to evaluate the cytologic features of canine AS and look for additional diagnostic criteria. METHODS: Cytologic specimens from 19 histologically and immunohistochemically confirmed cases of canine AS were extensively reviewed for cytologic features. We compared cytologic, histopathologic, and immunohistochemical findings. RESULTS: Neoplastic cells in 14 cytology specimens had a high-grade sarcomatous appearance, whereas in 4 specimens the cells were extremely pleomorphic, ranging from sarcomatous to epithelioid. In the remaining case, the neoplastic cells were low grade, spindle shaped, and monomorphic. Other relevant cytologic findings were blood contamination (18/19 cases), cellular cohesiveness (16/19), punctate cytoplasmic vacuolation (19/19), background neutrophilia (11/19) and eosinophilia (5/19), erythrophagocytosis (8/19), extramedullary hematopoiesis (8/19), and apoptotic leukocytes (14/19). Vasoformative features (ie, pseudoacinar structures) were observed in 7 of 19 samples. Histologically, 16 neoplasms had a proliferative pattern typical of well-differentiated canine AS. Three tumors were atypical poorly differentiated AS; 2 of these had a striking epithelioid pattern and 1 was a poorly differentiated spindle cell tumor with focal vascular differentiation. Immunohistochemically, tumor cells in 16 cases were positive for both endothelial markers tested (Factor VIII-related antigen [FVIII-ra] and CD31 antigen), 2 were positive for CD31 only, and 1 was positive for FVIII-ra only. The epithelioid AS were negative for cytokeratins. CONCLUSIONS: The cytologic characteristics of canine AS are widely heterogeneous, but supplementary findings can provide clues that are useful for making a cytologic diagnosis. Histologic and immunohistochemical confirmation is nonetheless warranted in all cases.     

Cytologic differentiation of benign from malignant canine mammary tumors

Cytologic and histologic examination of 91 canine mammary masses was performed by two cytologists and two histopathologists. Ten important cytologic criteria of malignancy for canine mammary tumors were identified. A cytologic grading system for differentiation of benign from malignant mammary tumors was proposed using these criteria. With this system, approximately one fourth of the malignant mammary tumors were given a concordant cytologic diagnosis. Approximately one-half of the benign masses were given a concordant cytologic diagnosis by the two cytologists. One-half of all the tumors examined were given inconclusive cytologic diagnoses by both cytologists. The cytologic identification of spindle cells did not differentiate complex and mixed mammary tumors from simple tumors. Only five of the animals studied died of mammary cancer, precluding a critical analysis of the cytologic criteria for prediction of cancer mortality.     

Cytologic examination of fine‐needle aspirates from mammary gland tumors in the dog: diagnostic accuracy with comparison to histopathology and association with postoperative outcome

Background: Mammary tumors are the most common neoplasms in female dogs. Malignant tumors may carry a poor prognosis and necessitate surgery. Few data are available on the value of cytologic examination as a diagnostic or prognostic tool for mammary tumors in dogs. Objectives: The objectives of this study were to determine whether cytologic findings in fine‐needle aspirate specimens of canine mammary tumors correlate with histopathologic results and whether the cytologic diagnosis is associated with postoperative outcome. Methods: In this prospective study, fine‐needle aspirate samples were obtained from 50 mammary tumors in 50 dogs. Results of cytologic and histopathologic examination were compared, using the histologic diagnosis as the reference method. Kaplan–Meier log rank analysis was used to evaluate univariate association of the cytologic diagnosis with duration of survival, local control, and metastasis‐free interval. Results: Adequate cytologic samples were obtained in 43/50 (86%) cases. The cytologic diagnosis correlated with the histologic diagnosis for benign and malignant tumors in 40/43 (93%) and 35/43 (81%) cases, respectively. Cytologic examination had a sensitivity of 88% and a specificity of 96% for the diagnosis of malignancy. The cytologic diagnosis had significant univariate association with duration of survival (P=.016), recurrence‐free interval (P=.003), and metastasis‐free interval (P=.014). Conclusions: Cytologic examination of mammary tumors in the dog has satisfactory accuracy, sensitivity, and specificity for the diagnosis of malignancy and is associated with postoperative outcome. Further studies on the diagnostic accuracy of cytology as well as multivariate analysis of its preoperative prognostic value in mammary tumors in the dog are warranted.     

Results of hyperamplification of centrosomes in naturally developing tumors of dogs.

OBJECTIVE: To evaluate results of centrosome hyperamplification in naturally developing tumors of dogs. SAMPLE POPULATION: Tumor specimens from 9 dogs with tumors (rhabdomyosarcoma, osteosarcoma, chondrosarcoma, myxosarcoma, and mammary gland tumor) and 2 canine osteosarcoma cell lines. PROCEDURE: 3 antibodies for centrosome proteins (ie, anti-gamma-tubulin, anti-BRCA1, and anti-pericentrin) were used for immunohistochemical analysis. Double immunostaining for centrosomes was used to confirm the specificity of these antibodies for centrosomes. Mutational analysis of the canine p53 gene was carried out by polymerase chain reaction-single-strand conformation polymorphism analysis, and expression of canine MDM2 protein was evaluated by use of immunohistochemical analysis, using anti-MDM2 antibody. RESULTS: Immunohistochemical analysis of dog osteosarcoma cell lines with apparent aneuploidy revealed frequent hyperamplification of centrosomes in the osteosarcoma cell lines. Similar hyperamplified centrosomes were detected in the tumor tissues from all of the 9 tumors. The frequency of cells with hyperamplified centrosomes (3 to 20/cell) in each tumor tissue ranged from 9.50 to 48.1%, whereas centrosome hyperamplification was not observed in normal lymph nodes from these dogs. In 8 of the 9 tumors, mutation of p53 gene or overexpression of MDM2, or both, was detected. CONCLUSIONS AND CLINICAL RELEVANCE: Various types of naturally developing tumors in dogs often have hyperamplification of centrosomes associated with chromosome instability. Hyperamplification of centrosomes is a novel tumor marker for use in cytologic and histologic examinations of clinical specimens obtained from dogs.     

Fine needle aspiration cytology of pilomatricoma in three dogs

Background — Fine needle aspiration cytology is being used for the diagnosis of various neoplasms, but we are unaware of reports dealing with the cytologic features of canine pilomatricoma.
Objective — The purpose of this report was to describe the cytologic features of pilomatricoma in 3 dogs.
Methods — Fine-needle aspirates were obtained from cutaneous masses using a 25-ga needle. Smears were prepared and stained with May-Grünwald-Giemsa and hematoxylin and eosin. The cutaneous masses were excised and routinely processed for histologic examination.
Results — Cytologic features of all 3 tumors included high cellularity and numerous clusters of tightly arranged of basaloid cells with evenly distributed chromatin and small distinct nucleoli surrounding sheets of "ghost cells". Ghost cells were characterized by a central unstained zone corresponding to the site previously occupied by the nucleus. Amorphous keratinized material was observed in 1 tumor. Histopathologic findings confirmed the diagnosis of pilomatricoma in all 3 cases.
Conclusions — Basaloid cells in association with ghost cells are important cytopathologic criteria that may provide a definitive cytologic diagnosis of pilomatricoma in dogs, and may help avoid a false diagnosis of malignancy.     

Cytology of canine malignant histiocytosis

Cytologic features of bone marrow, tissue, and abdominal fluid in seven cases of malignant histiocytosis in dogs are described, and histopathology, hematology, and serum biochemistry of the cases are reviewed. Diagnosis of malignant histiocytosis was confirmed by tissue morphology and immunohistochemistry; neoplastic cells in all cases had positive immunoreactivity to lysozyme. This stain can be used to definitively establish the diagnosis of malignant histiocytosis on cytology specimens as well as tissue sections. Cytologic findings included numerous pleomorphic, large, discrete mononuclear cells with abundant, lightly basophilic, vacuolated, granular cytoplasm. Nuclei were round to oval to reniform with marked anisocytosis and anisokaryosis; nucleoli were prominent. Mitotic figures, often bizarre, were occasionally seen. Multinucleated giant cells and phagocytosis of erythrocytes and leukocytes were prominent features in cytologic preparations in four cases. Four dogs were anemic, five dogs were thrombocytopenic, and three dogs were hypercalcemic. Breeds affected included Doberman Pinscher (1), Golden Retriever (2), Flat Coated Retriever (3), and mixed-breed dog (1).     

Cytology of a mass on the meningeal surface of the left brain in a dog

An 11-year-old neutered male Labrador Retriever presented to Tufts University School of Veterinary Medicine for a 2-week history of seizures and altered behavior. Magnetic resonance imaging (MRI) revealed a homogeneously enhancing mass involving the surface of the left temporal, parietal, and occipital lobes of the brain, causing secondary hydrocephalus. Cytology samples obtained during rostrotentorial craniectomy contained abundant amorphous pink material suggestive of neuropil, scattered leukocytes, capillary fragments, large polyhedral nerve cell bodies, and other smaller cells with pale blue cytoplasm that occasionally were vacuolated and contained fine eosinophilic granules. The cytologic diagnosis was neoplasia, possibly meningioma. Ninety days after surgery the patient was euthanized after MRI results confirmed regrowth of the tumor. Histologic samples of the meningeal lesion collected at necropsy consisted of sheets and nests of loosely packed, large polygonal cells that compressed the brain parenchyma. The cytoplasm was eosinophilic and slightly granular, whereas nuclei were dense and eccentric. Neoplastic cells stained positive for S-100 protein, periodic acid-Schiff, and were partially diastase resistant. Vimentin staining was negative. Ubiquitin staining was light but diffusely positive. Ultrastructural features of the neoplastic cells included numerous secondary lysosomes and irregular pleomorphic nuclei. The final diagnosis was meningeal granular cell tumor. This case documents the cytologic and histologic features of an uncommon type of meningeal tumor.