Malignant peripheral nerve sheath tumor in a cat

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citológico e hematologia de cães e gatos. Medvet, São Paulo. Gross TL ... McGavin MD, Zachary JF (2013) Bases da Patologia em Veterinária. Elsevier, Rio de ...

Comparative Clinical Pathology


Malignant peripheral nerve sheath tumor in a cat: cytological, histopathological, and immunohistochemical aspects Bianca Santana de Cecco 1 & Taiara Muller da Silva 2 & Diandra Visentini Felin 3 & Verônica Metz Weber 3 & Lara Seffrin Dutra 3 & Glaucia Denise Kommers 2 & Cinthia Melazzo de Andrade 2 Received: 27 November 2017 / Accepted: 5 February 2018 # Springer-Verlag London Ltd., part of Springer Nature 2018

Abstract The malignant peripheral nerve sheath tumor is an uncommon tumor in cats. Cytological preparations can be used to diagnose such neoplasia, being a useful tool to characterize a spindle cell tumor presenting several criteria of malignancy. Histopathological examination is required for a definitive diagnosis, complemented by immunohistochemical techniques. This paper describes a case of malignant peripheral nerve sheath tumor in a cat. The diagnosis of mesenchymal neoplasm with high pleomorphism was suggested by cytology, performed through fine needle aspiration. Thereafter, the nodule underwent surgical excision, histopathological analysis, and immunohistochemistry. For immunohistochemical analysis, the panel included vimentin, S-100 protein, GFAP, von Willebrand factor, and cytokeratin. The markers that showed positive immunolabeling were vimentin and S-100 protein, confirming the mesenchymal origin of the tumor. It is possible to conclude that cytology was useful and reliable to pre-diagnose the neoplasm in this case. Added to the convenience and short time for execution of the technique, the aspiration cytology is recommended to suggest a diagnosis in similar cases and support the clinical management of the patient. Keywords Cytology . Neoplasia . Schwannoma . Feline medicine

Schwannoma or peripheral nerve sheath tumor (PNST) is a neoplasm associated to the roots of the peripheral nerves, including those of Schwann cells derived from the neural crest and responsible for the myelination of the peripheral nerve system, as well as the fibroblast connective tissue surrounding nerve bundles (Raskin and Meyer 2011). In cats, it is an uncommon tumor, described most commonly in the head and neck, as well as in the central and peripheral nervous system (Watrous et al. 1999; Buza et al. 2012; Okada et al. 2007).

* Bianca Santana de Cecco [email protected] 1

Veterinary Pathology Department, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil


Veterinary Pathology Department, Federal University of Santa Maria, Santa Maria, RS, Brazil


Department of Veterinary Clinical Pathology, Federal University of Santa Maria, Santa Maria, RS, Brazil

Based on the biological and morphological characteristics, the PNST are divided in benign (BPNST) or malignant (MPNST) (Brower et al. 2005). The malignant tumors showed more anaplastic cytological characteristics and aggressive growth invading the adjacent normal tissue, compared to other tumors (McGavin and Zachary 2013; Gross et al. 2005). When observed in cytology samples, MPNST presents low cellularity and shows a few clusters of mesenchymal cells. Sometimes, axon fragments obtained from the aspirate make the diagnosis easier (Koestner and Higgins 2002). Microscopically, the MPNST have several morphological patterns, and some common features are anaplasia, high mitotic index, necrosis, adjacent tissue invasion, and distant organs metastasis, commonly affecting the lungs (Stoica et al. 2001). Cytology is a useful diagnostic tool, since it is easy to practice, minimally invasive, and the result is achieved quickly, what gives the clinician the support to choose a treatment (Cowell et al. 2009). The cytological exam is performed as a trial exam, to define the cell type and to determine the malignancy characteristics of these cells as anaplasia, anisokaryosis,

Comp Clin Pathol

and nuclear features (Raskin and Meyer 2011). However, definitive diagnosis is obtained through the histopathological exam and immunohistochemistry. This case report has an objective to describe the cytological, histopathological, and immunohistochemical aspects of a MPNST in a cat, comparing the results of techniques and highlighting the fine-needle aspiration cytology (FNAC) as a useful and reliable technique. Considering the tumors located in the head region in cats, MPNST should be cited as a differential diagnosis. A female cat, mixed breed, unneutered, 11 years old, arrived in the Academic Veterinary Hospital of the Federal University of Santa Maria (UFSM), presenting an itching cutaneous nodule on the head (Fig. 1) with the history of 4 months of growth that seemed to be growing fast. The animal had the history of squamous carcinoma in the ears 5 years ago, went through surgical removal followed by sun restriction, and had no recurrence. The veterinary clinician who was responsible for the case asked for complementary exams such as blood analysis, blood biochemistry, and FNAC. Blood analysis and biochemistry were unremarkable. FNAC revealed a highly cellular sample with large spindle cells displayed in clusters or individually presenting a marked pleomorphism. These cells had a cytoplasm that varied from moderate to intensely basophilic and discretely vacuolated; the nuclei were ovoid with significant anisokaryosis, course chromatin, multiple prominent and pleomorphic nucleoli, and nuclear molding. Frequently, binucleated and multinucleated

Fig. 1 Feline female, mixed breed, 11 years old. Macroscopic appearance of the tumor before surgical excision, ulcerated mass adhered to the adjacent soft tissues

cells were seen. It was also observed a moderate number of small lymphocytes and a large amount of eosinophilic extracellular matrix. These findings were suggestive of peripheral nerve sheath tumor. The differential diagnoses were sarcomas and hemangiopericytoma. Based on the physical examination and cytology, the surgical excision of the nodule was chosen as treatment and definitive diagnosis tool. The mass was then forwarded to histopathology at the Veterinary Pathology Laboratory in UFSM. The macroscopic exam showed a white, multilobulated mass with yellow areas invading the dermis. When cut, the mass was soft with homogeneously white cutting surface. Microscopically, it was observed a non-delimited and nonencapsulated mass, composed by a neoplastic cell proliferation displayed in mantle extending from the superficial dermis to the deep dermis. The cells were arranged in parallel, in a wavy pattern, and sometimes, swirling. The stroma was plentiful and occasionally collagen and small amount of myxoid matrix were observed. In the areas of low cellularity, the cells had a fusiform shape; some were oval and others were polyhedral (higher density area) with an eosinophilic cytoplasm. The chromatin was predominantly dense and sometimes vesiculated, especially in areas of high cell density. The nucleoli were conspicuous and varied in size. The pleomorphism and cellular atypia were more pronounced in areas of high cell density. One to two mitotic figures per high power field and mild inflammatory infiltrate of lymphocytes were present. Histopathological diagnosis confirmed the suspicion of malignant peripheral nerve sheath tumor, previously suggested by FNAC. In order to complement the histopathological analysis, an immunohistochemistry panel was performed (Fig. 2). The markers used were glial fibrillary acidic protein (GFAP), von Willebrand factor, vimentin, S-100 protein, and cytokeratin. In this case, the markers that showed a positive result were vimentin and S-100 protein. Vimentin is a marker with high expression in mesenchymal cells, and schwannoma as already mentioned is a tumor of mesenchymal origin. The neoplastic cells stained intensely and diffusely for S-100 protein as well. Cytokeratin is a marker for epithelial cells and was used to rule out an epithelial origin of the tumor; as expected, the immunolabeling was negative. Neoplastic cells were negative for von Willebrand, ruling out the main differential diagnosis for MPSNT, which are endothelial cell tumors such as hemangiopericytoma. GFAP was not reactive at all because of the lack of central nervous system tissue. This report emphasizes the importance and reliability of FNAC as a screening test for inflammatory and neoplastic lesions. Cytologic evaluation represents a fast, convenient, and easy technique, which most of the time corresponds to the final diagnosis, giving support to clinical management

Comp Clin Pathol Fig. 2 Malignant peripheral nerve sheath tumor in a cat. a Cytology of the tumor. Spindle mesenchymal cells are observed, presenting elongated shape and the presence of extracellular matrix (fast panoptic, × 100). b Photomicrograph of the same case that of a, highlighting the morphology of the cells, characterized by an elongated fusiform shape with basophilic cytoplasm and some multinucleated cells. (fast panoptic, × 400). c Histopathology of the case. It is observed a wavy pattern of the spindle mesenchymal cells with abundant myxoid stroma and matrix (H&E, × 100). d Histopathology, showing the wavy pattern which can sometimes form swirls. e Immunohistochemistry with antivimentin. (DAB, × 100). f Microphotography immunohistochemistry demonstrating positive labeling for S-100 protein

of patients. The veterinary clinician was able to start quickly the treatment based on the FNAC diagnostic. This exam was also important to choose the surgery technique appropriated for the patient. In addition, we conclude that the malignant peripheral nerve sheath tumor should be included as a differential diagnosis for cutaneous and subcutaneous tumors in cats, especially those located on the head and neck.

Compliance with ethical standards Conflict of interest The authors declare that they have no conflict of interest. Informed consent Informed consent was obtained from all individual participants included in the study. Ethical approval All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.

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