CASE REPORT published: 17 June 2022 doi: 10.3389/fvets.2022.905302 Case Report: Neuroblastoma-Like Schwannoma in a Domestic Short-Haired Cat Vivian S. Chen 1 , Andrew W. Bollen 2 , Paola Marco-Salazar 3 , Robert J. Higgins 4† and Sílvia Sisó 4,5* 1 Charles River Laboratories, Inc., Durham, NC, United States, 2 Neuropathology Division, Department of Pathology, School of Medicine, University of California, San Francisco, San Francisco, CA, United States, 3 Department of Medicine and Animal Surgery, School of Veterinary Medicine, Autonomous University of Barcelona (UAB), Bellaterra, Spain, 4 Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States, 5 Translational Imaging and Pathology, Codiak BioSciences, Cambridge, MA, United States An axillary mass was detected in a 6-year-old, neutered, male, domestic short-haired cat during a wellness exam. Gross examination following surgical removal revealed a discrete, deep subcutaneous, discoid mass that was between 0.5- and 0.7-cm-in-diameter and diffusely firm and white. Histologically, the mass was well-demarcated, partially encapsulated, and expanded the panniculus carnosus. It was Edited by: Andrea Tipold, composed of tightly packed, giant rosettes of radially arranged fusiform cells stacked University of Veterinary Medicine in one to 10 layers with peripherally palisading nuclei and with centrally oriented, Hannover, Germany fibrillary, cytoplasmic processes, and collagenous fibers. Laminin immunoreactivity and Reviewed by: ultrastructural examination highlighted a continuous basal lamina outside the plasma Maria Teresa Mandara, University of Perugia, Italy membrane of each neoplastic cell. Neoplastic cells were immunoreactive for GFAP, Jéssica Molín, S100, periaxin, and Sox-10 and were immunonegative for synaptophysin, smooth Universitat de Lleida, Spain muscle actin, and pancytokeratin. Collective findings were consistent with a diagnosis of *Correspondence: Sílvia Sisó neuroblastoma-like schwannoma. This is the first veterinary report of this rare variant of neuropathvetnet@gmail.com benign schwannoma. † Deceased Keywords: schwannoma, neurilemoma, peripheral nerve sheath tumor, neuroblastoma, cat Specialty section: This article was submitted to INTRODUCTION Veterinary Neurology and Neurosurgery, In cats, cutaneous schwannomas, which are grouped within the entity of benign peripheral nerve a section of the journal sheath tumors (PNST), occur predominantly in the head or neck and, with less frequency, in the Frontiers in Veterinary Science limbs or the trunk (1). Recent studies of a large feline case series found that PNST comprised at Received: 26 March 2022 least 7% of all skin tumors and are more common than previously reported (2). Schwannomas are Accepted: 23 May 2022 usually characterized histologically by fusiform cells organized in a storiform pattern with nuclear Published: 17 June 2022 palisading, and with alternating patterns of compact, cellular (Antoni type A) to loosely arranged, Citation: myxoid (Antoni type B) streams and fascicles of spindloid cells (3). However, classification of Chen VS, Bollen AW, Marco-Salazar P, schwannomas in domestic animal species is challenging due to the small number of histological Higgins RJ and Sisó S (2022) Case studies, often the absence of distinct PNST features, and the lack of a diagnostic panel of Report: Neuroblastoma-Like Schwannoma in a Domestic spatial biomarkers for confirming the histogenesis of neoplastic cells (3). Moreover, morphologic Short-Haired Cat. variants of schwannomas that are recognized in human medicine, such as “ancient” schwannoma Front. Vet. Sci. 9:905302. or epithelioid schwannoma, have been rarely reported in domestic animals (3, 4). In the cat, doi: 10.3389/fvets.2022.905302 schwannomas have been lumped broadly under the category of benign or malignant PNST without Frontiers in Veterinary Science | www.frontiersin.org 1 June 2022 | Volume 9 | Article 905302 Chen et al. Neuroblastoma-Like Schwannoma in a Cat any distinction between schwannomas, perineuriomas, or routinely processed for transmission electron microscopic neurofibromas (1, 2). Neuroblastoma-like schwannoma is a examination. For light microscopy, 5-µm tissue sections were variant of benign schwannoma that has rarely been described stained with haematoxylin and eosin (H&E), Masson’s trichrome in people and not previously in a domestic animal species stain or processed for immunohistochemistry (IHC) using 1- (4). This variant has unique histomorphologic features, and h incubation periods with one of several primary antibodies the immunophenotypic characteristics are consistent with a (Table 1). The panel of primary antibodies included those to histogenesis from Schwann cells. laminin, glial fibrillary acidic protein (GFAP), S-100, periaxin, Sox-10, smooth muscle actin (SMA), synaptophysin and Ki- CASE PRESENTATION 67. Table 1 summarizes details of the vendors, the different IHC reagents and antigen unmasking protocols used for each A 6-year-old, neutered, male, domestic short-haired cat was antibody. Negative controls in which either diluent or normal presented to the William R. Pritchard Veterinary Medical serum was substituted for the respective primary antibody were Teaching Hospital (VMTH), University of California – Davis, included in the study, and standardized positive control tissue, as California, USA, for a wellness examination, including an used in the UCD VMTH histology laboratory, was included for evaluation of an axillary mass that was first noted by the owners each antibody where appropriate. 2 weeks prior to the visit. Prior medical history included feline Histologically, there was a discrete, multilobular and partially herpes virus-1 infection and symblepharon of the left eye as a encapsulated mass that focally expanded the panniculus carnosus kitten, and mild overconditioning and mild dental disease as in the vicinity of hypercellular peripheral nerve fascicles. an adult. The stretched capsule surrounding the mass consisted of The mass was palpated as approximately 1-cm-in-diameter, epineurium and a few residual nerve fibers (Figure 1A). The round, firm and partially adhered to the muscle and connective lobules, which were separated by variably thick bands of tissue of the left lateral thoracic wall and axilla. Examination of dense connective tissue, varied in size, and were composed of a fine needle aspirate of the mass was tentatively diagnosed as a multiple tightly packed, 5- to 300-µm-in-diameter, fibrillar, giant feline basal cell tumor and the owners elected surgical removal of rosettes. Each rosette was characterized by radially-arranged, the mass. It was removed ∼1 week later with 1- to 2-cm lateral fusiform cells with indistinct cell borders, and twisted nuclei margins and with one fascial plane deep to the mass. At surgery, stacked in one to 10 layers at the periphery with often the mass was discoid, between 0.5- and 0.7-cm-in-diameter and prominent nuclear palisading (Figures 1B,C). The center of diffusely firm and white. The fresh specimen was trimmed, the rosettes was composed of various amounts of trichrome- and most sections were immediately immersion-fixed in 10% positive collagen fibrils (Figure 1D) and of indistinct fibrillar buffered formalin for 24 h and then processed and embedded and eosinophilic cytoplasmic processes, which were laminin in paraffin wax. Additional tissue sections were submitted in immunoreactive (Figure 1E). The nuclei were round to oval Karnovsky’s fixative to California Animal Health and Food and occasionally indented with mostly stippled chromatin Safety Services Laboratory Systems (CAHFS, Davis, CA) and and variably distinct nucleoli. Anisocytosis and anisokaryosis TABLE 1 | Panel of antigenic markers used by immunohistochemistry. Primary antibody Provider; Location Pre-treatment Primary Secondary antibody Detection system (Catalog number) antibody (catalog number) dilution Synaptophysin (SY38, Dako; Carpinteria, CA, USA Heat induced epitope 1:80 Mouse Dako Envision+ system-HRP (K4006) Vector NovaRed SYN) (M0776) retrieval (HIER) (SK-4800) Steamer-30’ Glial fibrillary acidic Dako; Carpinteria, CA, USA Proteinase K-5’ 1:600 Rabbit Dako Envision+ system-HRP (K4006) Vector NovaRed protein (GFAP) (Z0334) (SK-4800) Laminin (LAM) BioGenex, (PU078-UP) 0.2% protease, 37C, 1:40 Rabbit Biocare Medical 4+ Detection Vector NovaRed 10’ System; Streptavidin-HRP (SK-4800) Anti-human Periaxin Sigma-Aldrich (57716) (HIER) Steamer-30’ 1:1000 Rabbit Biocare Medical 4+ Detection Vector NovaRed System; Streptavidin-HRP (SK-4800) Anti-human Sox-10 Santa Cruz (SC-17342) (HIER) Steamer-30’ 1:100 Rabbit Biocare Medical 4+ Detection Vector NovaRed System; Streptavidin-HRP (SK-4800) S-100 Vector VP-S276 (HIER) Steamer-30’ 1:600 Rabbit Biocare Medical 4+ Detection Vector NovaRed System; Streptavidin-HRP (SK-4800) Smooth Muscle Actin BioGenex (MU128-UC) Steam EDTA-9, 30’ 1:300 Mouse Dako Envision+ system-HRP (K4006) Vector NovaRed (1A4; SMA) (SK-4800) Ki-67 Dako; Carpinteria, CA, USA (HIER) Steamer-30’ 1:40 Mouse Biocare Medical 4+ Detection Vector NovaRed (M7240) System; Streptavidin-HRP (SK-4800) Frontiers in Veterinary Science | www.frontiersin.org 2 June 2022 | Volume 9 | Article 905302 Chen et al. Neuroblastoma-Like Schwannoma in a Cat FIGURE 1 | Neuroblastoma-like schwannoma, cat, subcutaneous mass. The FIGURE 2 | Neuroblastoma-like schwannoma, cat, subcutaneous mass. mass is composed of multiple lobules that are separated by variably thick Immunohistochemistry. Neoplastic Schwann cells cytoplasmic processes bands of dense connective tissue (arrow). Note the hypercellular peripheral diffusely and strongly immunoreact to periaxin (A). One hundred percent of nerve fascicles (asterisk) in the vicinity of the mass, which is partially nuclei of neoplastic cells are strongly positive for Sox-10 (inset) (B). Neoplastic encapsulated by the epineurium. H&E stain (A). The lobules are composed of Schwann cell cytoplasmic processes immunoreact to S-100 (C). Neoplastic multiple, tightly packed, 5–300-µm-in-diameter, fibrillar, giant rosettes that fibrillary cytoplasmic processes are strongly labeled with glial fibrillary acid exhibited a characteristic cellular polarity with a peripheralized nucleus and protein (D). Immunohistochemistry for synaptophysin confirms lack of centrally oriented cytoplasm. Note that there is nuclear palisading. H&E stain immunoreactivity of neoplastic cells (E). Approximately 10% of the cells display (B). Each individual giant rosette is characterized by radially-arranged fusiform nuclear ki-67 (MIB-1) immunostaining (F). cells with round to oval, lymphocyte-like nuclei and eosinophilic fibrillary cytoplasm. H&E (C). Giant rosettes contain a centralized collagen core (in blue). Masson’s trichrome stain (D). Each fibrillar and eosinophilic cytoplasmic neoplastic process, similar to each Schwann cell in healthy peripheral nerves numbers of nucleoli. Re-examination of the initial cytological (asterisk), diffusely and strongly immunoreacts to laminin. Immunohistochemistry for laminin (E). Each neoplastic cell is coated by a smear (Supplementary Figure 1) confirmed the pattern of giant well-formed, continuous, 50 nm thick, electron-dense basal lamina investing rosettes with piling of elongated nuclei at the periphery and long and interdigitating cytoplasmic processes. The cytoplasm contains a centrally-oriented, fibrillary processes. flattened, often invaginated nucleus, microfibrils and sparse organelles with a A final diagnosis of neuroblastoma-like schwannoma was few mitochondria, ribosomes, and lysosome-like granules. TEM micrograph (F). made based on the cytomorphological features and the strong immunoreactivity to laminin, which characteristically highlighted basal lamina around each neoplastic Schwann cell. Additional immune markers revealed that neoplastic cells were were mild, and mitotic figures were occasional (3 mitotic also strongly immunoreactive to GFAP, S-100, periaxin, and Sox- figures in 10 400x fields). Variably areas of intratumoral 10 but with no immunoreactivity to synaptophysin and SMA coagulative necrosis were occasional throughout. Very small (Figures 2A–F). The proliferative index was 10, as calculated by numbers of lymphocytes, plasma cells, and rare neutrophils the proportion of Ki-67-positive nuclei in a total count of 2,000 were scattered within the mass, mostly surrounding lobules. cells. Previous studies on feline benign PNSTs reported neoplastic Ultrastructural examination of neoplastic cells corroborated cells as mostly consistently immunoreactive for laminin, variably a well-formed, continuous basal lamina investing long and immunoreactive to S-100 and GFAP, and minimally to SMA interdigitating cytoplasmic processes (Figure 1F). Multifocally, (1, 2). In this study, two additional relatively novel Schwann cell variable amounts of collagen fibrils were deposited extracellularly markers, periaxin and Sox-10, supported the histogenesis of this (Supplementary Figure 1). Neoplastic cells exhibited sparse neoplasm as a schwannoma. Both markers have been evaluated organelles with a few mitochondria, ribosomes, and lysosome- in canine PNSTS together with laminin (3). Periaxin is required like granules and had twisted and indented nuclei and variable for maintenance of the myelin sheath that is formed from the Frontiers in Veterinary Science | www.frontiersin.org 3 June 2022 | Volume 9 | Article 905302 Chen et al. Neuroblastoma-Like Schwannoma in a Cat cell membrane of Schwann cells (5), and Sox-10 is expressed in AUTHOR CONTRIBUTIONS some cells of the Schwann cell lineage of peripheral nerves and enhances Schwann cell responsiveness to axonal neuregulin and VC was the UC Davis anatomic-pathology resident who received cell survival (6). and work-out the case. PM-S was a visiting Ph.D. student Rosette formation with strong immunolabeling of neoplastic who work-out the IHC of the case. SS was the UC Davis cells with neuronal-specific immune biomarkers such as Neuropathology Fellow who act as the reviewer neuropathologist synaptophysin, is a characteristic feature of neuroblastomas and lead the diagnostic immunohistochemical approach. RH (3). This lack of immunoreactivity, together with the other and AB were the expert opinion senior neuropathologists results of immunophenotyping, confirmed a neuroblastoma- who help diagnose the case. All authors contributed to like schwannoma as the definitive diagnosis. Consistent with the diagnosis of the case and concept of the case report reports in people, this rare variant of schwannoma has strong and writing. S-100 immunoreactivity and primarily occurs as a solitary and sporadic mass in the dermis and subcutaneous tissues with FUNDING scattered reports in other sites, such as the orbit and as a pleural mass in the posterior mediastinum (7–10). A total of 25 This study was initiated and completed at the VMTH of neuroblastoma-like schwannomas have been reported in people, UC Davis during VC’s last year of residency in anatomic preferentially female and aged from 16 to 64 years old (8, 10, pathology and SS as a Fellow in Neuropathology, UC Davis, 11). Differential diagnoses include the hyalinizing spindle cell Davis. This study was funded by the Center for Companion tumor with giant rosettes, a variant of low-grade fibromyxoid Animal Health at UC Davis (CCAH Alloc.# 2013-35-R siso). sarcoma, which despite mimicking the histomorphology of PM-S was supported by an AGAUR Ph.D. visiting grant neuroblastoma-like schwannoma, has a malignant behavior and [2012 BE100584] from the Generalitat de Catalunya, Barcelona, is not immunoreactive to S-100 (10). Catalunya, Spain. In summary, this is the first report of neuroblastoma-like schwannoma in a domestic animal. The histologic hallmark ACKNOWLEDGMENTS of this variant of schwannomas is the uniform rosette histoarchitecture. Despite they can resemble Homer-Wright We would like to thank Mike Manzer, Barry Puget, Kurt rosettes, they are much larger than those seen in neuroblastomas, Takahashi, and Cristopher Kwong in the UCD VMTH lack immunoreactivity to synaptophysin and display strong histology laboratory for their superb histological and immunoreactivity to Schwann cell markers like laminin, S-100 immunohistochemical technical support. We thank Scott and Sox-10. Also, their centers appeared to be composed of Fish and Michele Parsiani in the electron microscopy service collagen rather than neurites, as demonstrated by histochemical at CAHFS for their technical expertise. We are thankful to stains and immunohistochemistry. Histological features that Dr. David Malarkey and Dr. Gordon Flake at NIEHS for their favored a benign diagnosis in this case include encapsulation, reviews of this article. lack of mitotic figures and absence of necrosis. At a 3-month follow-up examination, a computerized tomography (CT) scan SUPPLEMENTARY MATERIAL demonstrated mild contrast enhancement of the left ventrolateral thoracic body wall subcutaneous tissue deep to the previous The Supplementary Material for this article can be found surgical scar, suggestive of either granulation tissue or recurrent online at: https://www.frontiersin.org/articles/10.3389/fvets. neoplasia. However, further contact for follow-up with the cat has 2022.905302/full#supplementary-material been lost. Supplementary Figure 1 | Neuroblastoma-like schwannoma, cat, subcutaneous mass. (A) Multifocally, variable amounts of scaffolds of ∼53 nm thick collagen fibrils (inset) form stacks along processes and in between basal laminae. DATA AVAILABILITY STATEMENT Transmission electron microscopy. (B) A cytological smear of the mass recapitulates the giant rosettes with prominent cellular polarity. 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