Diagnostic immunohistochemistry of primary and secondary central nervous system neoplasms of dogs and cats

The diagnosis of primary and secondary CNS neoplasms of dogs and cats relies on histologic examination of autopsy or biopsy samples. In addition, many neoplasms must be further characterized by immunohistochemistry (IHC) for a more refined diagnosis in specific cases. Given the many investigations assessing the diagnostic and prognostic IHC profile of CNS neoplasms in the veterinary literature, it may be difficult for the diagnostic pathologist or pathology trainee to narrow the list of reliable diagnostic IHCs when facing a challenging case. Here we compile a comprehensive list of the most diagnostically relevant immunomarkers that should be utilized for the diagnostic support or confirmation of the most common primary and secondary CNS neoplasms of dogs and cats.

Clinical, magnetic resonance imaging, and histological description of a choroid plexus papilloma with disseminated intraventricular and spinal cerebrospinal fluid drop metastases in a young adult dog: a case report

A 2-year-old male entire Cane Corso was presented for investigations into a 1-week history of ambulatory paraparesis and pelvic limb ataxia gradually deteriorating. Magnetic resonance imaging (MRI) revealed intraventricular space-occupying lesions affecting the fourth ventricle and lateral apertures and intradural-extramedullary space-occupying lesions at the level of C7 vertebra, L4-L5, and L7-S1 intervertebral disk spaces. Due to poor quality of life, the patient was euthanized. A post-mortem examination revealed partially encapsulated, multifocally infiltrative, and moderately cellular neoplastic masses. The histological description was similar for all masses. The cells appeared cuboidal with round central nuclei and a moderate amount of eosinophilic cytoplasm and were arranged almost exclusively in single-layered papilliform patterns supported by a fibrovascular stroma. Mitoses were rarely observed (1/2.37 mm2). The primary neoplasm was morphologically most consistent with a choroid plexus papilloma despite drop metastases. This is the first report of a histologically confirmed primary ventricular choroid plexus papilloma causing disseminated MRI-apparent intraventricular and spinal drop metastases.

The Analysis of E-Cadherin, N-Cadherin, Vimentin, HER-2, CEA, CA15-3 and SF Expression in the Diagnosis of Canine Mammary Tumors

Canine mammary tumors (CMTs) are one of the most common tumors in female dogs, and they are associated with a poor prognosis owing to their high rate of recurrence and metastasis rates, which make their diagnosis especially important in clinical veterinary medicine. In this study, the characteristics of tumors were observed in dogs suffering from CMTs, and clinical diagnosis and histopathology were used to identify tumors. Furthermore, the expression levels of tumor markers for CMTs were analyzed by enzyme-linked immunosorbent assay (ELISA) and quantitative PCR (qPCR). Upon clinical examination, dogs with CMTs displayed a distinct and irregular mass in the mammary gland, and X-ray (Latero-lateral and ventro-dorsal views) and ultrasonography of the abdomen revealed a moderately echogenic mass at the mammary gland with slightly stronger density than the surrounding tissue. A total of 30 tumors were identified by histopathology, 11 benign and 19 malignant. Changes in some indicators in dogs suffering from CMTs and healthy dogs suggested that there were multiple direct or paraneoplastic changes associated with tumors that could be detected/suspected by hematological examination, and ELISA revealed the HER-2 serum concentrations were significantly different between healthy animals and those with malignant tumors. qPCR indicated that tumor markers N-cadherin, Vimentin, HER-2, CEA, CA15-3 and SF were higher in dogs with malignant tumors than healthy dogs, with a low level of E-cadherin in malignant tumors. This study verified that serological tests and molecular biological tests were essential to the early diagnosis, treatment and prognosis of dogs with tumors.

Use of a telovelar approach for complete resection of a choroid plexus tumor in a dog

OBJECTIVE

To describe a telovelar approach to the fourth ventricle for excision of a choroid plexus tumor within the ventricle.

ANIMAL

A 3-year-old entire male Chihuahua.

STUDY DESIGN

Case report METHODS: A 3-year-old dog with two-month history of progressive vestibular signs and subdued mentation was diagnosed with a fourth ventricle tumor. Gross total resection of the tumor was achieved through a telovelar approach to the fourth ventricle.

RESULTS

Complete removal of the tumor was confirmed on immediate postoperative MRI. The dog recovered from the surgical procedure without complications, displaying some neurological deficits as preoperatively. His neurological examination was normal 2 weeks after surgery and remained so until the time of writing this case report (28 months) without additional treatment.

CONCLUSION

The telovelar approach allowed complete excision of a choroid plexus tumor located in the fourth ventricle of the dog reported here.

Spinal ectopic choroid plexus papilloma in a cat

Case summary

A 10-year-old male neutered Russian Blue cat was presented with a 2-month history of progressive non-ambulatory paraparesis. Spinal MRI revealed a well-demarcated, compressive intradural extramedullary mass at the level of T1 vertebra. The mass had subtle hyperintensity on T2-weighted images, was isointense on T1-weighted images and had diffuse, marked enhancement following gadolinium administration. Neuroaxis MRI, including limited brain sequences, excluded other visible lesions. Thoracic and abdominal radiographs were unremarkable. The mass was resected via a dorsal C7–T2 laminectomy and durotomy. Histopathology revealed a neoplasm composed of columnar-to-polygonal cells forming bilayered palisading patterns with a few apical cilia. Three mitoses were noted in 10 high-power fields. This was consistent with an epithelial neoplasm and initially a metastatic adenocarcinoma was considered most likely. Full-body CT with contrast and including the brain found rhinitis but did not identify any additional neoplastic foci. Biopsies of the nasal cavity and fine-needle aspiration of the spleen and liver were unremarkable. On immunohistochemical evaluation, pan-cytokeratin and E-cadherin immunolabelling was observed; however, synaptophysin, thyroglobulin, chromogranin A and glial fibrillary acidic protein was not detected. This, along with the histological morphology and absence of a primary tumour, was compatible with an ectopic choroid plexus neoplasm. Follow-up performed at 3, 14 and 24 months postoperatively revealed neurological improvement without recurrence.

Relevance and novel information

We describe the presentation, histopathological and immunohistochemical features and outcome of a case of a rare ectopic choroid plexus neoplasm in the spinal cord of a cat.

Role of Cadherins in Cancer-A Review

Cadherins play an important role in tissue homeostasis, as they are responsible for cell-cell adhesion during embryogenesis, tissue morphogenesis, differentiation and carcinogenesis. Cadherins are inseparably connected with catenins, forming cadherin-catenin complexes, which are crucial for cell-to-cell adherence. Any dysfunction or destabilization of cadherin-catenin complex may result in tumor progression. Epithelial mesenchymal transition (EMT) is a mechanism in which epithelial cadherin (E-cadherin) expression is lost during tumor progression. However, during tumorigenesis, many processes take place, and downregulation of E-cadherin, nuclear β-catenin and p120 catenin (p120) signaling are among the most critical. Additional signaling pathways, such as Receptor tyrosine kinase (RTK), Rho GTPases, phosphoinositide 3-kinase (PI3K) and Hippo affect cadherin cell-cell adhesion and also contribute to tumor progression and metastasis. Many signaling pathways may be activated during tumorigenesis; thus, cadherin-targeting drugs seem to limit the progression of malignant tumor. This review discusses the role of cadherins in selected signaling mechanisms involved in tumor growth. The clinical importance of cadherin will be discussed in cases of human and animal cancers.

E-Cadherin Expression in Canine Melanocytic Tumors: Histological, Immunohistochemical, and Survival Analysis

E-cadherin, a glycoprotein involved in cell-cell adhesion, has a pivotal role in epithelial-mesenchymal transition, a process through which neoplastic epithelial cells develop an invasive phenotype. In human cutaneous melanomas, decreased E-cadherin expression is associated with shorter survival and increased Breslow thickness, whereas in the dog its role is poorly understood. Tumor thickness and modified Clark level were recently proposed as useful features to assess canine melanocytic tumors, but no studies investigated their association with E-cadherin expression. We performed immunohistochemistry on 77 formalin-fixed, paraffin-embedded primary canine melanocytic tumors. A 3-tier and a 2-tier classification system for assessing E-cadherin expression were tested, with the latter being more informative for the assessment of canine melanocytic tumors. E-cadherin expression was lower in cutaneous melanomas than melanocytomas, as well as in amelanotic tumors compared to pigmented tumors. In amelanotic melanomas, absent E-cadherin expression was associated with an unfavorable outcome, suggesting a potential use of this marker in defining the prognosis of amelanotic melanomas. E-cadherin expression was lower in tumors with greater tumor thickness and modified Clark level ≥IV, suggesting its possible utility in identifying the most invasive tumors. The expression of E-cadherin in oral melanomas was heterogeneous, but was associated with pigmentation and clinical outcome; thus, E-cadherin evaluation could be advantageous to detect the most aggressive neoplasms. However, cutaneous melanomas without E-cadherin expression frequently had a favorable clinical outcome. Hence, its importance as prognostic factor should be carefully considered depending on the tumor origin.

Choroid plexus and the blood-cerebrospinal fluid barrier in disease

The choroid plexus (CP) forming the blood-cerebrospinal fluid (B-CSF) barrier is among the least studied structures of the central nervous system (CNS) despite its clinical importance. The CP is an epithelio-endothelial convolute comprising a highly vascularized stroma with fenestrated capillaries and a continuous lining of epithelial cells joined by apical tight junctions (TJs) that are crucial in forming the B-CSF barrier. Integrity of the CP is critical for maintaining brain homeostasis and B-CSF barrier permeability. Recent experimental and clinical research has uncovered the significance of the CP in the pathophysiology of various diseases affecting the CNS. The CP is involved in penetration of various pathogens into the CNS, as well as the development of neurodegenerative (e.g., Alzheimer´s disease) and autoimmune diseases (e.g., multiple sclerosis). Moreover, the CP was shown to be important for restoring brain homeostasis following stroke and trauma. In addition, new diagnostic methods and treatment of CP papilloma and carcinoma have recently been developed. This review describes and summarizes the current state of knowledge with regard to the roles of the CP and B-CSF barrier in the pathophysiology of various types of CNS diseases and sets up the foundation for further avenues of research.

Canine Primary Intracranial Cancer: A Clinicopathologic and Comparative Review of Glioma, Meningioma, and Choroid Plexus Tumors

In the dog, primary intracranial neoplasia represents ~2-5% of all cancers and is especially common in certain breeds including English and French bulldogs and Boxers. The most common types of primary intracranial cancer in the dog are meningioma, glioma, and choroid plexus tumors, generally occurring in middle aged to older dogs. Much work has recently been done to understand the characteristic imaging and clinicopathologic features of these tumors. The gross and histologic landscape of these tumors in the dog compare favorably to their human counterparts with many similarities noted in histologic patterns, subtype, and grades. Data informing the underlying molecular abnormalities in the canine tumors have only begun to be unraveled, but reveal similar pathways are mutated between canine and human primary intracranial neoplasia. This review will provide an overview of the clinicopathologic features of the three most common forms of primary intracranial cancer in the dog, delve into the comparative aspects between the dog and human neoplasms, and provide an introduction to current standard of care while also highlighting novel, experimental treatments that may help bridge the gap between canine and human cancer therapies.

Clinicopathologic Features, Diagnosis, and Characterization of the Immune Cell Population in Canine Choroid Plexus Tumors

The World Health Organization characterizes human choroid plexus tumor (CPT) as papilloma (CPP), atypical CPP (ACPP), and carcinoma (CPC). CPCs can disseminate via cerebrospinal fluid and be mistaken for metastatic carcinoma, creating a diagnostic challenge. Kir7.1 immunohistochemistry (IHC) is a highly reliable tool for diagnostic confirmation of CPTs and their differentiation from metastatic carcinomas in human beings and dogs. This study describes the neuropathology, Kir7.1 staining profile, and the immune cell population within the tumor microenvironment in 11 CPTs in dogs. Archived tissue sections with a diagnosis of CPT were examined and immunolabelled with Kir7.1 for diagnostic confirmation. The number of Ki67-positive neoplastic cells was calculated in 2.4 mm² (equivalent to 10 FN22/40X fields), and a mean value was generated for each neoplasm. IHC for CD3, CD20, MAC387, and Iba1 was performed for immune cell characterization, and the number of stained cells for each antibody was counted in 2.4 mm², generating individual cumulative values for each antibody. T-tests with Bonferroni correction evaluated IHC differences between tumor types, and Spearman's rank correlations evaluated relationships among IHC markers. Kir7.1 immunoreactivity was intense at the apical cell membrane in CPPs and ACPPs, and at the apical cell membrane and cytoplasm in CPCs. Ki67 immunoreactivity was detected in all cases. CD3+ and CD20+ lymphocytes trended together (p = 0.005) and were present within and around all CPTs. Five cases had intravascular MAC387+ monocytes. Iba1 immunoreactivity was robust within and around all tumors. Statistical differences in immune cell markers were not found among tumor types. As previously reported, Kir7.1 is a reliable antibody for the diagnosis of canine CPTs. Although immune cells were present in all cases, no significant associations were found between the type of cells and tumor diagnosis. The characterization of the immune cells within CPTs could be useful in future studies involving immunotherapy.

Comparative Cytogenetic Analysis of Dog and Human Choroid Plexus Tumors Defines Syntenic Regions of Genomic Loss

Choroid plexus tumors (CPTs) occur spontaneously in humans and dogs providing an opportunity for comparative cross species analysis of common tumor mechanisms. Large scale chromosomal copy number alterations are the hallmark of human CPTs and identification of driver genes within these regions is problematic. Copy number alterations in 12 spontaneous dog CPTs were defined using an Illumina 170 K single nucleotide polymorphism array and were characterized by highly recurrent whole chromosomal losses in up to 100% of cases with few chromosome wide gains. Loss of canine chromosomes 2, 5, 8, and 20 were seen in 90%-100% of cases and included regions syntenic to loci within commonly reported whole chromosome losses in human choroid plexus tumors. These regions included previously defined tumor suppressor clusters on chromosome 3p and 17p as well as genes associated with chromosomal instability such as TP53 and VHL. This karyotypic signature is similar to a previously defined hypodiploid subgroup of human choroid plexus carcinomas. The nonrandom, highly recurrent alterations in dog CPTs suggest specific selection pressures and oncogenic mechanisms are present. More extensive analysis of this spontaneous tumor model is warranted and may provide key insights into driver mechanisms common to both species.

Canine Ependymoma: Diagnostic Criteria and Common Pitfalls

Reports of canine ependymoma are generally restricted to single case reports with tumor incidence estimated at 2% to 3% of primary central nervous system (CNS) tumors. While most commonly reported in the lateral ventricle, tumors can occur anywhere in the ventricular system and in extraventricular locations. Rosettes and pseudorosettes are a common histologic feature; however, these features can be mimicked by other CNS neoplasms. Thirty-seven potential ependymoma cases were identified in a retrospective database search of 8 institutions, and a histologic review of all cases was conducted. Of 37 cases, 22 candidate cases were further subjected to a consensus histologic and immunohistochemical review, and only 5 of 37 (13.5%) were conclusively identified as ependymoma. The neuroanatomic locations were the lateral ventricle (3/5), third ventricle (1/5), and mesencephalic aqueduct (1/5). Subtypes were papillary (4/5) and tanycytic (1/5). Histologic features included rosettes (5/5), pseudorosettes (5/5), ependymal canals (2/5), tanycytic differentiation (1/5), blepharoplasts (1/5), ciliated cells (1/5), and high nuclear to cytoplasmic ratio (5/5). Immunolabeling for GFAP (4/4) and CKAE1/3 (3/4) was found in pseudorosettes, rosettes, and scattered individual neoplastic cells. Diffuse but variably intense cytoplasmic S100 immunolabeling was detected in 3 of 4 cases. Olig2 intranuclear immunolabeling was observed in less than 1% of the neoplastic cells (3/3). Tumors that had pseudorosettes and mimicked ependymoma included oligodendroglioma, choroid plexus tumor, pituitary corticotroph adenoma, papillary meningioma, and suprasellar germ cell tumor. These findings indicate that canine ependymoma is an extremely rare neoplasm with histomorphologic features that overlap with other primary CNS neoplasms.

Glomeruloid Microvascular Proliferation, Desmoplasia, and High Proliferative Index as Potential Indicators of High Grade Canine Choroid Plexus Tumors

Choroid plexus tumors (CPT) are intraventricular neoplasms accounting for 10% of all primary central nervous system tumors in dogs. They are frequently classified according to the human WHO classification into choroid plexus papilloma (CPP, grade I), atypical CPP (aCPP, grade II), and choroid plexus carcinoma (CPC, grade III). Histological features observed in canine CPT such as increased vascular density (IVD) and glomeruloid microvascular proliferation (GMVP) are not part of the WHO classification. This multi-centric study aimed to investigate tumor-associated vascular hyperplasia in dogs by determining the prevalence of GMVP and IVD in 52 canine CPT and their association with tumor grade. In addition, the expression of angiogenic factors was assessed by immunohistochemistry in 25 tumors to investigate the pathogenesis of tumor-associated vascular hyperplasia. Based on the classical histological hallmarks, this study of 52 CPT identified 22 (42%) CPP (grade I) and 30 of (58%) CPC (grade III). GMVP was more prevalent in CPC (13/30; 43%) than CPP (1/22; 4%), whereas IVD occurred to a similar extent in CPP and CPC. Desmoplasia was more common in CPC (19/30; 63%) than CPP (2/22; 9%), and similarly, the proliferative index (PI) of neoplastic epithelium was significantly higher in CPC (5.14%) than CPP (0.94%). The majority of CPT expressed platelet-derived growth factor (PDGF), PDGFRα, PDGFRβ, and vascular endothelial growth factor (VEGF) irrespective of tumor grade or tumor-associated vascular hyperplasia. These results suggest that tumor-associated GMVP, desmoplasia, and PI may serve as histological indicators of malignancy in CPT.