Bilateral Aural Masses with Malignant Transformation to Sebaceous Adenocarcinoma and Osseous Invasion in a German Shepherd Dog: A Case Report

Bilateral Aural Masses with Malignant Transformation to Sebaceous Adenocarcinoma and Osseous Invasion in a German Shepherd Dog: A Case Report | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report Bilateral Aural Masses with Malignant Transformation to Sebaceous Adenocarcinoma and Osseous Invasion in a German Shepherd Dog: A Case Report Rana Vafaei, Hamzeh Soltaninejad, Mohammad Reza Esmailinejad, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7789950/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background : Sebaceous gland tumors are among the most common cutaneous neoplasms in dogs and are generally benign. However, malignant transformation into sebaceous adenocarcinoma is rare and may result in local invasion or metastasis. Cytological examination plays a crucial role in the initial evaluation of canine cutaneous and ear canal masses, facilitating differentiation between benign and malignant lesions. Aims : This case report aimed to describe an unusual presentation of bilateral malignant aural sebaceous tumors with osseous invasion in a German Shepherd dog, emphasizing the diagnostic value of cytology in identifying malignant transformation within otherwise benign-appearing sebaceous lesions. Methods : A four-year-old intact male German Shepherd dog was presented with bilateral obstructive ear canal masses. Fine-needle aspiration (FNA) cytology was performed on both lesions, and skull radiographs were obtained to assess potential bone involvement. Cytological smears were evaluated for cellular morphology, population diversity, and evidence of malignancy. Results : Cytology revealed two distinct cellular populations: (1) large clusters of mature sebaceous epithelial cells consistent with a benign sebaceous component and (2) smaller, cohesive clusters of basaloid reserve cells showing marked cytological atypia characterized by anisokaryosis, high nuclear-to-cytoplasmic ratio, and multiple prominent nucleoli. These findings were compatible with sebaceous adenoma exhibiting foci of malignant transformation. Radiographic examination demonstrated osteolytic changes of the temporal bones, supporting the presence of invasive behavior. The owner declined further diagnostic and therapeutic interventions. Conclusion : This case highlights the importance of comprehensive cytological evaluation in sebaceous gland tumors to detect malignant components that may be overlooked in mixed lesions. The bilateral presentation and evidence of bone invasion underscore the potential for locally aggressive behavior and emphasize the need for histopathological confirmation when cytological findings suggest malignancy. Canine Sebaceous adenocarcinoma Ear canal tumor Osseous invasion German Shepherd Case report BMC Figures Figure 1 Figure 2 Figure 3 Background Sebaceous gland tumors account for approximately 6.8% to 8.3% of all cutaneous neoplasms in dogs (Goldschmidt and Shofer 1992 ). The vast majority are benign sebaceous adenomas or epitheliomas. Sebaceous adenocarcinomas are uncommon, representing less than 10% of all sebaceous tumors, and are characterized by local invasiveness and a low to moderate metastatic potential, often to regional lymph nodes and lungs (Scott et al. 2001 ; Vail and Withrow 2019 ). The external ear canal is a common site for various tumors in dogs, with ceruminous gland adenocarcinomas being the most frequently reported malignant type (London et al. 1996 ). The presentation of primary sebaceous adenocarcinoma within the ear canal, especially bilaterally, is exceptionally rare. This malignancy's aggressive behavior can lead to devastating local effects, including invasion of the underlying tympanic bulla and petrous temporal bone (Marino et al. 1994 ). This case report details the diagnostic findings and ethical dilemma in a young German Shepherd dog with bilateral sebaceous adenocarcinomas originating from the ear canals, with confirmed radiographic evidence of bone invasion, for which the owner elected no treatment. Case presentation A four-year-old, 38 kg, intact male German Shepherd dog was referred to the oncology service for evaluation of bilateral aural masses (Fig. 1). The owner reported a six-month history of persistent head shaking, otorrhea, and malodor, which was initially managed as chronic otitis by the primary veterinarian. Medical management with topical and systemic antibiotics and anti-inflammatories provided minimal improvement. Over the previous two months, progressive growth of masses within both ear canals was noted. Clinical Findings: On physical examination, the dog was bright, alert, and responsive. Vital parameters were within normal limits. Dermatological examination revealed bilateral, firm, ulcerated, and erythematous masses completely obstructing the vertical ear canals. Both pinnae were thickened, and a foul-smelling, hemorrhagic discharge was present. Otoscopic examination beyond the masses was impossible. No significantly enlarged mandibular or superficial cervical lymph nodes were palpated. Diagnostic Investigations: Cytology: Fine-needle aspiration of both masses was performed. Cytological evaluation revealed clusters of basaloid reserve cells and more mature sebaceous epithelial cells with moderate anisocytosis and anisokaryosis (Fig. 2 A). Numerous inflammatory cells (neutrophils and macrophages) were also present. The initial cytological interpretation was consistent with a sebaceous adenoma with secondary inflammation (Fig. 2 B & C). Diagnostic Imaging: Lateral and oblique radiographs of the skull were performed. The images revealed distinct, mottled lytic areas affecting the temporal bones adjacent to both tympanic bullae (Fig. 3). There was no evidence of soft tissue mineralization within the masses. Thoracic radiographs in three views were unremarkable, with no signs of pulmonary metastasis. Treatment and Outcome: A multidisciplinary team discussed treatment options with the owner. The recommended course was aggressive local therapy involving bilateral total ear canal ablation (TECA) and lateral bulla osteotomy (LBO), followed by histopathological margin evaluation and consideration of adjunctive radiotherapy due to the confirmed bone invasion. The prognosis with treatment was guarded due to the extent of invasion but was considered the only potential option for local control or cure. After extensive counseling, the owner declined all therapeutic interventions, including palliative care, citing financial constraints and concerns over the dog's quality of life post-operatively, given the bilateral nature of the required procedure. The dog was discharged with instructions for monitoring quality of life. Follow-up communication two months later revealed that the dog's condition had deteriorated significantly, and the owner elected for euthanasia on welfare grounds. No necropsy was permitted. Discussion and Conclusions This case presents several unusual and clinically significant features. First, the bilateral occurrence of a malignant sebaceous gland tumor in the ear canals is a highly uncommon presentation, with most previous reports describing unilateral ceruminous gland carcinomas (London et al. 1996 ; Marino et al. 1994 ). Second, the presence of osseous invasion on radiographs at the time of diagnosis indicates a highly aggressive local disease process (Mukherjee et al. 2011 ). Third, this aggressive behavior manifested in a relatively young dog, whereas most cutaneous neoplasms are typically diagnosed in older animals (Rodrigues 2025 ). The cytological and histopathological findings underscore a critical diagnostic challenge. The initial FNA primarily sampled the benign (adenoma) component of the tumor, highlighting the limitation of cytology in diagnosing malignancy within heterogeneous masses. Definitive diagnosis required histopathological examination of deep tissue biopsies, which identified the foci of adenocarcinoma. This emphasizes the importance of deep and multiple biopsies for any persistent or invasive aural mass. The owner's decision to forgo treatment presents a common ethical challenge in veterinary medicine. While advanced, the disease was potentially manageable with radical surgery. This case illustrates the complex interplay between advanced medical options, financial limitations, and perceptions of animal welfare. It reinforces the need for clear, compassionate communication regarding prognosis with and without treatment. In conclusion, this case report serves to alert clinicians that: Sebaceous adenomas, though often benign, can undergo malignant transformation. Aural masses in dogs, even in young patients, require thorough investigation, including diagnostic imaging to assess for bone involvement. Deep-tissue biopsy is essential for a definitive diagnosis; as superficial samples may not be representative. Sebaceous adenocarcinoma should be considered a differential diagnosis for invasive aural masses, and its potential for aggressive local behavior warrants early and aggressive intervention. Abbreviations FNA: Fine-Needle Aspiration TECA: Total Ear Canal Ablation LBO: Lateral Bulla Osteotomy Declarations Ethics approval and consent to participate: Not applicable for a case report per institutional policy. Funding: No funding was received for this case report. Author Contribution All authors contributed to the management of the case, writing, and editing of the manuscript. All authors read and approved the final manuscript. Acknowledgement The authors thank the clinical pathology and diagnostic imaging departments for their contributions. Data Availability All data generated during this case are included in this published article. The histopathology slides and radiographs are stored in the hospital's medical records. References Goldschmidt MH, Shofer FS (1992) Skin Tumors of the Dog and Cat. Pergamon Press. London CA, Dubilzeig RR, Vail DM, Ogilvie GK, Hahn KA, Brewer WG, Hammer AS, O'Keefe DA, Chun R, McEntee MC, McCaw DL (1996) Evaluation of dogs and cats with tumors of the ear canal: 145 cases (1978-1992). Journal of the American Veterinary Medical Association, 208(9), 1413-1418. Marino DJ, MacDonald JM, Matthiesen DT, Patnaik AK (1994) Results of surgery in cats with ceruminous gland adenocarcinoma. Journal of the American Animal Hospital Association, 30, 54–58. Mukherjee D, Chaichana KL, Adogwa O, Gokaslan Z, Aaronson O, Cheng JS, McGirt MJ (2011) Association of extent of local tumor invasion and survival in patients with malignant primary osseous spinal neoplasms from the surveillance, epidemiology, and end results (SEER) database. World neurosurgery. 76(6), 580-585. Rodrigues BL (2025) Linfoma cutâneo epiteliotrópico em cão jovem: Relato de caso. Pubvet, 19(05):e1770-. Scott DW, Miller WH, Griffin CE (2001) Muller & Kirk's Small Animal Dermatology (6th ed.). W.B. Saunders. Vail DM, Withrow SJ. (2019) Withrow & MacEwen's Small Animal Clinical Oncology (6th ed.). Elsevier. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7789950","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":550766200,"identity":"93edd101-111d-4e92-8bd9-1e076be678fe","order_by":0,"name":"Rana Vafaei","email":"","orcid":"","institution":"University of Tehran","correspondingAuthor":false,"prefix":"","firstName":"Rana","middleName":"","lastName":"Vafaei","suffix":""},{"id":550766201,"identity":"9f254774-efaf-4da4-84a4-5a5ce98b8072","order_by":1,"name":"Hamzeh Soltaninejad","email":"","orcid":"","institution":"Shahid Bahonar University of 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1","display":"","copyAsset":false,"role":"figure","size":122649,"visible":true,"origin":"","legend":"\u003cp\u003eGross appearance of the mass on the external ear canal, presenting as a firm and irregular mass.\u003c/p\u003e","description":"","filename":"Figure1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7789950/v1/086fa52fca1573f08bba578d.jpeg"},{"id":96917857,"identity":"1380ed61-1516-46b5-9346-1f9479726e01","added_by":"auto","created_at":"2025-11-27 14:10:38","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":130355,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCytological assessment of Sebaceous Gland Tumors. A \u003c/strong\u003eFine-needle aspirate cytology of the masses. Note the cohesive cluster of well-differentiated sebaceous epithelial cells with abundant, vacuolated cytoplasm and small, round, central nuclei (Wright-Giemsa stain, 100x). \u003cstrong\u003eB and C \u003c/strong\u003emalignant transformation in the same specimen. Exhibiting marked cellular pleomorphism, high nuclear to cytoplasmic ratio, and multiple nucleoli. (Wright-Giemsa stain, 100x).\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7789950/v1/024edcc6d8c98c47bf564cc2.jpg"},{"id":96847510,"identity":"b03a165e-4f26-4ac5-a98b-52d3f3f1b2e2","added_by":"auto","created_at":"2025-11-26 16:50:55","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":156938,"visible":true,"origin":"","legend":"\u003cp\u003eLateral \u003cstrong\u003e(A)\u003c/strong\u003e and ventrodorsal \u003cstrong\u003e(B)\u003c/strong\u003e radiographic views of the canine skull. Black arrows indicate osteolytic changes of the temporal bone. White arrows highlight a soft tissue opacity within the external ear canal, consistent with the malignant mass and suggesting possible local invasion.\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7789950/v1/225adadf0df5eebb4ff8c03e.jpg"},{"id":97136452,"identity":"af58977f-ec70-49c0-9bac-4b14ae8b5580","added_by":"auto","created_at":"2025-12-01 09:56:36","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":854551,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7789950/v1/a0e6fa3a-e5ff-411c-b4f2-d28fa0af1461.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Bilateral Aural Masses with Malignant Transformation to Sebaceous Adenocarcinoma and Osseous Invasion in a German Shepherd Dog: A Case Report","fulltext":[{"header":"Background","content":"\u003cp\u003eSebaceous gland tumors account for approximately 6.8% to 8.3% of all cutaneous neoplasms in dogs (Goldschmidt and Shofer \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). The vast majority are benign sebaceous adenomas or epitheliomas. Sebaceous adenocarcinomas are uncommon, representing less than 10% of all sebaceous tumors, and are characterized by local invasiveness and a low to moderate metastatic potential, often to regional lymph nodes and lungs (Scott et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Vail and Withrow \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe external ear canal is a common site for various tumors in dogs, with ceruminous gland adenocarcinomas being the most frequently reported malignant type (London et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1996\u003c/span\u003e). The presentation of primary sebaceous adenocarcinoma within the ear canal, especially bilaterally, is exceptionally rare. This malignancy's aggressive behavior can lead to devastating local effects, including invasion of the underlying tympanic bulla and petrous temporal bone (Marino et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1994\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThis case report details the diagnostic findings and ethical dilemma in a young German Shepherd dog with bilateral sebaceous adenocarcinomas originating from the ear canals, with confirmed radiographic evidence of bone invasion, for which the owner elected no treatment.\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cp\u003eA four-year-old, 38 kg, intact male German Shepherd dog was referred to the oncology service for evaluation of bilateral aural masses (Fig. 1). The owner reported a six-month history of persistent head shaking, otorrhea, and malodor, which was initially managed as chronic otitis by the primary veterinarian. Medical management with topical and systemic antibiotics and anti-inflammatories provided minimal improvement. Over the previous two months, progressive growth of masses within both ear canals was noted.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Findings:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOn physical examination, the dog was bright, alert, and responsive. Vital parameters were within normal limits. Dermatological examination revealed bilateral, firm, ulcerated, and erythematous masses completely obstructing the vertical ear canals. Both pinnae were thickened, and a foul-smelling, hemorrhagic discharge was present. Otoscopic examination beyond the masses was impossible. No significantly enlarged mandibular or superficial cervical lymph nodes were palpated.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDiagnostic Investigations:\u003c/strong\u003e\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003eCytology:\u003c/strong\u003e Fine-needle aspiration of both masses was performed. Cytological evaluation revealed clusters of basaloid reserve cells and more mature sebaceous epithelial cells with moderate anisocytosis and anisokaryosis (Fig. 2 A). Numerous inflammatory cells (neutrophils and macrophages) were also present. The initial cytological interpretation was consistent with a sebaceous adenoma with secondary inflammation (Fig. 2 B \u0026amp; C).\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eDiagnostic Imaging:\u003c/strong\u003e Lateral and oblique radiographs of the skull were performed. The images revealed distinct, mottled lytic areas affecting the temporal bones adjacent to both tympanic bullae (Fig. 3). There was no evidence of soft tissue mineralization within the masses. Thoracic radiographs in three views were unremarkable, with no signs of pulmonary metastasis.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eTreatment and Outcome:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA multidisciplinary team discussed treatment options with the owner. The recommended course was aggressive local therapy involving bilateral total ear canal ablation (TECA) and lateral bulla osteotomy (LBO), followed by histopathological margin evaluation and consideration of adjunctive radiotherapy due to the confirmed bone invasion. The prognosis with treatment was guarded due to the extent of invasion but was considered the only potential option for local control or cure.\u003c/p\u003e\n\u003cp\u003eAfter extensive counseling, the owner declined all therapeutic interventions, including palliative care, citing financial constraints and concerns over the dog\u0026apos;s quality of life post-operatively, given the bilateral nature of the required procedure. The dog was discharged with instructions for monitoring quality of life. Follow-up communication two months later revealed that the dog\u0026apos;s condition had deteriorated significantly, and the owner elected for euthanasia on welfare grounds. No necropsy was permitted.\u003c/p\u003e"},{"header":"Discussion and Conclusions","content":"\u003cp\u003eThis case presents several unusual and clinically significant features. First, the bilateral occurrence of a malignant sebaceous gland tumor in the ear canals is a highly uncommon presentation, with most previous reports describing unilateral ceruminous gland carcinomas (London et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Marino et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). Second, the presence of osseous invasion on radiographs at the time of diagnosis indicates a highly aggressive local disease process (Mukherjee et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Third, this aggressive behavior manifested in a relatively young dog, whereas most cutaneous neoplasms are typically diagnosed in older animals (Rodrigues \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe cytological and histopathological findings underscore a critical diagnostic challenge. The initial FNA primarily sampled the benign (adenoma) component of the tumor, highlighting the limitation of cytology in diagnosing malignancy within heterogeneous masses. Definitive diagnosis required histopathological examination of deep tissue biopsies, which identified the foci of adenocarcinoma. This emphasizes the importance of deep and multiple biopsies for any persistent or invasive aural mass.\u003c/p\u003e\u003cp\u003eThe owner's decision to forgo treatment presents a common ethical challenge in veterinary medicine. While advanced, the disease was potentially manageable with radical surgery. This case illustrates the complex interplay between advanced medical options, financial limitations, and perceptions of animal welfare. It reinforces the need for clear, compassionate communication regarding prognosis with and without treatment.\u003c/p\u003e\u003cp\u003eIn conclusion, this case report serves to alert clinicians that:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSebaceous adenomas, though often benign, can undergo malignant transformation.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eAural masses in dogs, even in young patients, require thorough investigation, including diagnostic imaging to assess for bone involvement.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eDeep-tissue biopsy is essential for a definitive diagnosis; as superficial samples may not be representative.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSebaceous adenocarcinoma should be considered a differential diagnosis for invasive aural masses, and its potential for aggressive local behavior warrants early and aggressive intervention.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eFNA: Fine-Needle Aspiration\u003c/p\u003e\n\u003cp\u003eTECA: Total Ear Canal Ablation\u003c/p\u003e\n\u003cp\u003eLBO: Lateral Bulla Osteotomy\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eEthics approval and consent to participate:\u003c/h2\u003e\n\u003cp\u003eNot applicable for a case report per institutional policy.\u003c/p\u003e\n\u003ch2\u003eFunding:\u003c/h2\u003e\n\u003cp\u003eNo funding was received for this case report.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eAll authors contributed to the management of the case, writing, and editing of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eThe authors thank the clinical pathology and diagnostic imaging departments for their contributions.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eAll data generated during this case are included in this published article. The histopathology slides and radiographs are stored in the hospital\u0026apos;s medical records.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eGoldschmidt MH, Shofer FS (1992) Skin Tumors of the Dog and Cat. Pergamon Press.\u003c/li\u003e\n \u003cli\u003eLondon CA, Dubilzeig RR, Vail DM, Ogilvie GK, Hahn KA, Brewer WG, Hammer AS, O\u0026apos;Keefe DA, Chun R, McEntee MC, McCaw DL (1996) Evaluation of dogs and cats with tumors of the ear canal: 145 cases (1978-1992). Journal of the American Veterinary Medical Association, 208(9), 1413-1418.\u003c/li\u003e\n \u003cli\u003eMarino DJ, MacDonald JM, Matthiesen DT, Patnaik AK (1994) Results of surgery in cats with ceruminous gland adenocarcinoma. Journal of the American Animal Hospital Association, 30, 54\u0026ndash;58.\u003c/li\u003e\n \u003cli\u003eMukherjee D, Chaichana KL, Adogwa O, Gokaslan Z, Aaronson O, Cheng JS, McGirt MJ (2011) Association of extent of local tumor invasion and survival in patients with malignant primary osseous spinal neoplasms from the surveillance, epidemiology, and end results (SEER) database. World neurosurgery. 76(6), 580-585.\u003c/li\u003e\n \u003cli\u003eRodrigues BL (2025) Linfoma cut\u0026acirc;neo epiteliotr\u0026oacute;pico em c\u0026atilde;o jovem: Relato de caso. Pubvet, 19(05):e1770-.\u003c/li\u003e\n \u003cli\u003eScott DW, Miller WH, Griffin CE (2001) Muller \u0026amp; Kirk\u0026apos;s Small Animal Dermatology (6th ed.). W.B. Saunders.\u003c/li\u003e\n \u003cli\u003eVail DM, Withrow SJ. (2019) Withrow \u0026amp; MacEwen\u0026apos;s Small Animal Clinical Oncology (6th ed.). Elsevier.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Canine, Sebaceous adenocarcinoma, Ear canal tumor, Osseous invasion, German Shepherd, Case report, BMC","lastPublishedDoi":"10.21203/rs.3.rs-7789950/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7789950/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e: Sebaceous gland tumors are among the most common cutaneous neoplasms in dogs and are generally benign. However, malignant transformation into sebaceous adenocarcinoma is rare and may result in local invasion or metastasis. Cytological examination plays a crucial role in the initial evaluation of canine cutaneous and ear canal masses, facilitating differentiation between benign and malignant lesions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAims\u003c/strong\u003e: This case report aimed to describe an unusual presentation of bilateral malignant aural sebaceous tumors with osseous invasion in a German Shepherd dog, emphasizing the diagnostic value of cytology in identifying malignant transformation within otherwise benign-appearing sebaceous lesions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e: A four-year-old intact male German Shepherd dog was presented with bilateral obstructive ear canal masses. Fine-needle aspiration (FNA) cytology was performed on both lesions, and skull radiographs were obtained to assess potential bone involvement. Cytological smears were evaluated for cellular morphology, population diversity, and evidence of malignancy.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e: Cytology revealed two distinct cellular populations: (1) large clusters of mature sebaceous epithelial cells consistent with a benign sebaceous component and (2) smaller, cohesive clusters of basaloid reserve cells showing marked cytological atypia characterized by anisokaryosis, high nuclear-to-cytoplasmic ratio, and multiple prominent nucleoli. These findings were compatible with sebaceous adenoma exhibiting foci of malignant transformation. Radiographic examination demonstrated osteolytic changes of the temporal bones, supporting the presence of invasive behavior. The owner declined further diagnostic and therapeutic interventions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e: This case highlights the importance of comprehensive cytological evaluation in sebaceous gland tumors to detect malignant components that may be overlooked in mixed lesions. The bilateral presentation and evidence of bone invasion underscore the potential for locally aggressive behavior and emphasize the need for histopathological confirmation when cytological findings suggest malignancy.\u003c/p\u003e","manuscriptTitle":"Bilateral Aural Masses with Malignant Transformation to Sebaceous Adenocarcinoma and Osseous Invasion in a German Shepherd Dog: A Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-26 16:50:50","doi":"10.21203/rs.3.rs-7789950/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5c249e3d-6ec6-4f5c-8564-18c3019cc6cc","owner":[],"postedDate":"November 26th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-27T14:53:29+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-26 16:50:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7789950","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7789950","identity":"rs-7789950","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}