Cytologic appearance of a keloidal fibrosarcoma in a dog

A 5-year-old neutered male, mixed-breed dog was presented with a single 4-mm, nodular, firm, haired subcutaneous mass on the left flank that had been present for approximately 2 weeks. Cytologic preparations of the mass revealed many spindle cells, few mast cells, rare eosinophils, rare macrophages, abundant hyalinized collagen, and moderate numbers of erythrocytes. The spindle cells were oval to fusiform, with oval nuclei, finely stippled to lacy chromatin, 1-5 variably sized prominent nucleoli, and moderate to abundant cytoplasm with indistinct cell borders, wispy cytoplasmic extensions, and occasionally, fine magenta granulation. The cell population exhibited moderate anisocytosis, moderate anisokaryosis, and rare binucleation. The eosinophilic material occurred both in large angular aggregates with blunt ends and in amorphous aggregates with fine wispy projections. Histologic findings were consistent with a keloidal fibrosarcoma. To the authors' knowledge, this report is the first to describe the cytomorphologic characteristics of a keloidal fibrosarcoma in a dog.     

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.     

Cytologic identification of immature endospores in a dog with rhinosporidiosis

An 8-year-old, intact, male Labrador Retriever was presented to the Boren Veterinary Medical Teaching Hospital at Oklahoma State University with a 2-month history of severe sneezing episodes that resulted in epistaxis and bilateral sanguineous discharge. Rhinoscopy revealed a small polypoid mass, and specimens were obtained for histopathology. Microscopic examination of formalin-fixed tissue specimens revealed organisms consistent with Rhinosporidium seeberi. The mass was surgically excised and impression smears were made for cytology examination. Smears revealed high numbers of endospores, typical of those previously described for R seeberi. In addition, numerous smaller structures, presumed to be immature endospores, were noted. The immature endospores were morphologically distinct from mature endospores and have not been described previously. Recognition of immature forms of Rhinosporidium may help prevent misidentification of the organism or misdiagnosis of a dual infection.     

MRI features of gliomatosis cerebri in a dog

The features of gliomatosis cerebri involving the brainstem and cerebellum in a 3-year-old dog are described. In magnetic resonance (MR) images, there was diffuse loss of the cerebellar folia and cerebellar gray and white matter contrast. Multiple illdefined T2-hyperintensities were present in the cerebellar parenchyma. A poorly defined, T2-hyperintense mass effect was present ventral to the pons and rostral medulla. No contrast enhancement was noted. Cerebrospinal fluid (CSF) was normal. Postmortem examination was consistent with gliomatosis cerebri, based on compatible histopathology and immunohistochemical findings. Although rare, gliomatosis cerebri should be included as a differential for diffuse infiltrative central nervous system (CNS) lesions.     

A true "triphasic" pattern: thoracolumbar spinal tumor in a young dog

An 8-month-old male Bernese Mountain Dog was referred with a history of hindlimb weakness that progressed to paresis on the right side. An intradural mass was detected in the spinal canal at the level of the 2nd and 3rd lumbar vertebrae. During surgical removal, 2 small fragments of the mass were prepared for cytologic examination by the squash technique. Cytologic examination revealed 3 different cell types: mesenchymal (stromal) cells, epithelial cells, and small undifferentiated hyperchromatic cells. On the basis of location and the triphasic cytologic pattern, a diagnosis of spinal nephroblastoma (thoracolumbar spinal tumor of young dogs) was made; histologic examination of the mass confirmed the cytologic diagnosis. To our knowledge, this is the first report of a triphasic pattern in a cytologic sample; recognizing this pattern is an important aid in reaching a definitive cytologic diagnosis.     

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.     

Presumptive Nocardia spp. infection in a dog treated with cyclosporin and ketoconazole

Abstract

CASE HISTORY: A dog that had received 8 months of cyclosporin and ketoconazole therapy for treatment of atopic dermatitis subsequently developed severe neurological disease, that failed to respond to treatment with trimethoprim-sulphadiazine and clindamycin.

HISTOPATHOLOGICAL FINDINGS: Histopathological examination of the pulmonary parenchyma and spinal cord revealed loose aggregates of Gram-positive, partially acid-fast, fine, beaded, filamentous bacteria, most consistent with Nocardia spp.

DIAGNOSIS: A presumptive diagnosis was made of disseminated nocardiosis of the spinal cord and lungs.

CLINICAL RELEVANCE: Nocardia spp. is an opportunistic actinomycete that may cause disseminated disease, particularly in immunocompromised animals. Cyclosporin is used in veterinary medicine to control immune-mediated and allergic disorders, with few reported adverse side effects. This case gives further evidence that involvement of the spinal cord in nocardiosis of the central nervous system (CNS) carries a poor prognosis, and opportunistic infection by Nocardia spp. may be a potential complication of immunosuppressive cyclosporin therapy in the dog.     

Nasal and oral masses in a dog

A 5-year-old, intact male, stray dog was presented in poor body condition, with pallor, muzzle deformity, multiple oozing fistulas with grass awns, bilateral sanguinopurulent nasal discharge and a fleshy friable mass occupying part of the hard palate. A friable mass occupying both nasal cavities was found on rhinoscopy. The dog had moderate nonregenerative normochromic-microcytic anemia, thrombocytopenia, hyperglobulinemia, and hypoalbuminemia. Cytologic preparations of the nasal and oral masses contained a neoplastic population of round cells with intracytoplasmic and extracellular vacuoles. Leishmania amastigotes also were observed, in the cytoplasm of macrophages and, occasionally, within neoplastic cells. A diagnosis of transmissible venereal tumor and concurrent leishmaniosis was made. Treatment with vincristine and allopurinol resulted in complete resolution of clinical signs and disappearance of the masses. The presence of amastigotes in neoplastic TVT cells may suggest an alternative mode of transmission of canine leishmaniosis where these diseases co-exist.     

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.     

Proliferative potential of a spinal nephroblastoma in a young dog

The proliferative potential of a spinal nephroblastoma was studied in a young dog. A 4-month-old, female golden retriever showed developing deterioration in her gait and subsequent paralysis of her hind legs. At necropsy, a well-demarcated grayish brown tumor mass was found in the lumbar spinal cord segments between L2 and L3. Histologically, a blastemal cell tumor with a tubule- or glomeruli-like structure was found to be infiltrating intradurally. Proliferating cells at the S-phase, assessed using the bromodeoxyuridine (BrdU) labeling method, were seen occasionally in the tubular cells and glomeruli-like structures and were frequently seen in the blastemal cells. Immunohistochemically, the tubular epithelial cells were positive for cytokeratin, and the blastemal cells were positive for vimentin. The present tumor showed a high potential for growth and invasion, which suggests that it the potential to expand into the adjacent spinal cord.     

Cytologic and immunohistochemical characterization of a lung carcinoid in a dog

An 11-year-old neutered male Yorkshire Terrier was presented to the Haemaru Referral Animal Hospital with a history of unresponsive tracheal collapse and an incidental finding of a lung nodule in the left caudal lung lobe on radiography. Thorough physical examination and imaging studies revealed no other masses. Cytologic examination of C-arm mobile fluoroscopy-guided fine-needle aspirates revealed numerous free nuclei and a low number of small round cells with moderate to abundant pale basophilic cytoplasm. Some cells contained indistinct basophilic granules in their cytoplasm, and extracellular pink material was noted. A caudal lung lobectomy was performed, and histologic evaluation of the mass revealed round to polygonal cells with abundant eosinophilic granular cytoplasm and round nuclei with mild anisokaryosis and 0-3 mitotic figures per high-power field. Cells were arranged in packets separated by fine fibrovascular stroma, suggestive of a pulmonary neuroendocrine neoplasm, specifically a carcinoma/carcinoid. The cells were immunoreactive for chromogranin A and neuron-specific enolase, and negative for cytokeratin, synaptophysin, calcitonin, thyroglobulin, parathyroid hormone, CD79a, light lambda, and vimentin. With these findings the tumor was diagnosed as a primary lung carcinoid. Eleven months after resection, there was no evidence of tumor regrowth or metastasis. The absence of necrosis, few mitotic figures, minimal pleomorphism, and benign behavior of this tumor resembled those of a typical carcinoid in humans.     

Cytologic features of a meningioma in a dog

Meningiomas are one of the most common nervous system tumors in dogs. They are mostly solitary, benign, intracranial tumors of the transitional type. Tentative diagnosis can usually be made on historical data, clinical and neurological signs, and radiographs, with an antemortem diagnosis confirmed by exploratory surgery and histologic evaluation of biopsy. The literature contains many reports of the gross, histological and ultrastructural morphology of canine meningiomas, but little on the cytologic features of these tumors. This report describes the cytologic appearance of an intracranial meningioma in a 9-year-old Miniature Schnauzer.     

Cytologic patterns of lymphadenopathy in canine monocytic ehrlichiosis

Background: Recognition of different cytologic patterns in lymph nodes (LNs) from dogs with canine monocytic ehrlichiosis (CME) and noninfectious causes of lymphoid reactivity may have diagnostic utility. Objectives: The aims of the present study were to compare cytologic patterns in LNs of dogs with different phases of CME, to investigate the association of cytologic pattern and presence of Ehrlichia spp. morulae, and to compare patterns of lymphoid reactivity between dogs with CME and those with noninfectious causes of lymphoid hyperplasia. Methods: Cytologic preparations of LNs from 35 dogs with nonmyelosuppressive CME (group A), 16 dogs with myelosuppressive CME (group B), 26 dogs with noninfectious diseases (group C), and 15 healthy dogs (group D) were evaluated. Percentages of lymphocyte types, plasma cells, macrophages, neutrophils, and eosinophils were determined. Samples from dogs in groups A and B were evaluated for the presence of morulae. Results: Cytologic abnormalities in LNs were recorded in 54% of dogs in group A, 88% in group B, 39% in group C, and 0% in group D and were more frequent (P=.02) in dogs with myelosuppressive CME than those with nonmyelosuppressive CME. Plasma cell hyperplasia was more frequent in CME than in noninfectious diseases (P=.03). An association between the presence of cytologic abnormalities and morulae in group A dogs was not found. Conclusions: Dogs with myelosuppressive CME have more lymphoid cytologic abnormalities than dogs with nonmyelosuppressive CME. LN plasmacytosis is the major pattern of lymphadenopathy in dogs with CME and is found more frequently in dogs with CME than in dogs with noninfectious causes of lymphadenopathy.     

Subcutaneous embryonal rhabdomyosarcoma in a dog: cytologic, immunocytochemical, histologic, and ultrastructural features

Abstract: A subcutaneous mass on the left antebrachium of an 11‐year‐old intact female English Pointer dog was evaluated presurgically by cytologic examination and immunocytochemical staining. The sample consisted of discrete, variably sized, markedly pleomorphic neoplastic cells that expressed vimentin with diffuse cytoplasmic staining, desmin with focal paranuclear staining, and myoglobin with diffuse cytoplasmic staining, consistent with a diagnosis of rhabdomyosarcoma. Lymphocytic and histiocytic markers were negative. Aspirates of the enlarged ipsilateral prescapular lymph node were positive for metastatic disease. Surgical excision of the tumor and lymph node were followed by histologic and electron microscopic examination. Histomorphologic appearance of neoplastic cells from the mass and the lymph node paralleled cytologic findings; the histologic diagnosis was round cell variant of embryonal rhabdomyosarcoma. By ultrastructural evaluation, cells contained numerous mitochondria and masses of cytoplasmic tangled myofilaments, features typical of rhabdomyoblasts. The dog received doxorubicin (30 mg/m²) every 3 weeks for 5 treatments. Local recurrence developed 6 months after resection but was not treated. Despite a guarded prognosis and untreated local recurrence, the dog was still alive 18 months after surgery. Cytologic evaluation and immunocytochemical staining were pivotal for the presurgical diagnosis of rhabdomyosarcoma.     

Cytologic and immunohistochemical characterization of a primitive neuroectodermal tumor in the brain of a dog

A 6-year-old intact female Pointer dog was presented for evaluation of acute onset of ataxia, circling, and head tilt. Neurologic assessment revealed overall decreased postural reaction, left-sided hemiparesis with incoordination, rigidity of fore- and hindlimbs, strabismus of the right eye, and bilateral horizontal nystagmus. Using magnetic resonance imaging, a mass lesion was identified in the cerebrum adjacent to the left side of the cerebellum compressing the brain stem ventrally. The mass was incompletely resected, and during surgery fine-needle aspiration and biopsy of the mass were performed. Cytologically, smears were highly cellular and contained predominantly small to medium-sized discrete round cells with high nuclear to cytoplasmic ratios and round nuclei with rare deep clefts or indentation, smooth chromatin, and indistinct nucleoli. Numerous cytoplasmic fragments were noted in the background. The primary diagnosis was lymphoma; other differential diagnoses included neuroendocrine tumor and poorly differentiated tumor of neural origin. The histologic diagnosis was lymphoma, and the lesion was presumed to be metastatic. On immunohistochemical analysis, the cells expressed neither CD3 nor CD79a. Re-examination of the histologic section revealed disorganized sheets of cells with multifocal palisading and perivascular arrangements of rosette-like structures. An expanded panel of antibodies to vimentin, cytokeratin, glial fibrillary acid protein (GFAP), neuron-specific enolase (NSE), synaptophysin (SYN), S-100, and CD45 was applied to histologic sections. Neoplastic cells were immunoreactive for vimentin, NSE, and S-100. Based on the histologic appearance and immunophenotype of the tumor, a diagnosis of primitive neuroectodermal tumor (PNET) was made. PNET, although rare in dogs, should be considered as a differential diagnosis for round cell tumors in the brain.     

Prostatic sarcomatoid carcinoma in a dog: cytologic and immunohistochemical findings

An 8-year-old neutered male Boxer was presented with tenesmus, hemorrhagic urethral discharge, and dysuria. Abdominal ultrasound and radiographic examinations revealed irregular prostatic enlargement. Laparotomy was performed and intraoperative cytology was done on imprint smears of a biopsy specimen obtained from a prostatic mass. The cytologic preparation was highly cellular and contained a predominant population of atypical, large, loosely cohesive spindle cells, with rare multinucleated cells and mitotic figures. The cytologic findings were consistent with undifferentiated sarcoma. At necropsy, a large cystic prostatic mass and numerous satellite nodules in the soft tissues around the pelvis were found. On histologic examination the tumor was composed primarily of bundles of neoplastic spindle cells. Rare pseudo-acinar structures and signet-ring cells also were observed. On immunohistochemical examination, the neoplastic cells co-expressed cytokeratin and vimentin. Based on histologic and immunohistochemical findings, the tumor was diagnosed as primary prostatic sarcomatoid carcinoma. This is a rare tumor in dogs, in which biphasic morphology of epithelial and mesenchymal cells can complicate the diagnosis, requiring immunochemical stains for confirmation.     

Cytologic patterns of lymphadenopathy in dogs infected with Leishmania infantum

BACKGROUND: Lymphadenopathy in canine leishmaniosis has been reported as reactive lymphoid hyperplasia or granulomatous (histiocytic) lymphadenitis. However, we are unaware of information on the effect of latent Leishmania infection on lymph node cytology compared with clinically affected dogs. OBJECTIVES: The aim of the present study was to investigate cytologic patterns of lymphadenopathy in dogs with clinical and subclinical forms of leishmaniosis and to correlate cytologic findings with the density of Leishmania amastigotes in fine needle aspiration (FNA) smears. METHODS: FNA cytology of prescapular or popliteal lymph nodes was evaluated on 32 dogs with clinical evidence of leishmaniosis (group A), 24 subclinically infected dogs (group B), and 17 clinically healthy noninfected dogs (group C); groups were based on the results of serologic and PCR tests for Leishmania sp. Differential nucleated cell counts (based on 300 cells) and amastigote density were determined microscopically. Cytologic findings were categorized and compared among groups. RESULTS: Cytologic abnormalities were found in 19 of 32 (59.4%) dogs in group A, 1 of 24 (4.2%) dogs in group B, and 2 of 17 (11.8%) dogs in group C and were significantly more frequent in group A than group B (P <.001) or C (P = .001). In group A, 68.7% of the dogs had lymphoid hyperplasia, 12.5% had lymphoid hyperplasia and histiocytic lymphadenitis, 6.3% had histiocytic lymphadenitis, and 3.1% had lymphoid hyperplasia and neutrophilic lymphadenitis. Lymphoid hyperplasia was also noted in 1 dog in group B, and lymphoid hyperplasia and eosinophilic lymphadenitis were each found in 1 dog in group C. Lymph node smears from 31 (96.9%) dogs in group A and 6 (25%) dogs in group B were positive for Leishmania amastigotes; however, no correlation was found between the density of amastigotes and cytopathologic patterns of lymphadenopathy. CONCLUSION: Abnormal lymph node cytology is much more common in dogs with clinical leishmaniosis than in dogs with subclinical infection, and primarily involves lymphoid hyperplasia. Despite finding no association between the density of amastigotes and type of lymphadenopathy, lymph node cytology still is a valuable diagnostic tool for diagnosing canine leishmaniosis.     

Myoclonus and hypercalcemia in a dog with poorly differentiated lymphoproliferative neoplasia

A 1‐year, 8‐month‐old Rhodesian Ridgeback was presented with obtundation, ambulatory tetraparesis, and myoclonus. Initial clinical findings included ionized hypercalcemia with an apparent marked increase in parathyroid hormone, thrombocytopenia, and nonregenerative anemia. Low numbers of circulating atypical cells were noted on blood film evaluation. Brain magnetic resonance imaging identified an extra‐axial contrast enhancing subtentorial lesion, and cerebrospinal fluid (CSF) analysis documented a marked atypical lymphocytic pleocytosis. Flow cytometry performed on the CSF demonstrated expression of only CD45, CD90, and MHC class II, with Pax5 positivity on subsequent immunohistochemistry. The final diagnosis was of B‐cell lymphoblastic lymphoma or acute leukemia, given the distribution of disease and the presence of significant bone marrow infiltration alongside an aggressive clinical course. The unusual immunophenotype of the neoplastic cells and hypercalcemia presented antemortem diagnostic challenges, highlighting the need for a multidisciplinary approach and caution in the interpretation of clinical abnormalities in cases with multiple comorbidities.