Metastatic mucinous adenocarcinoma from breast mimicking a pyogenic granuloma in the gingiva: a case report.

Mucin-producing adenocarcinomas (MAC) are an extremely rare, indistinct group of neoplasm having either a salivary gland origin or with prominent glandular component. The diagnosis is chiefly based on the histological aspect conjoined with immunohistochemical evaluation as clinico-radiographical features are non-specific. It can arise as a primary metastasis to soft tissues, most commonly from either lung, breast, kidney, or colon. This paper reports a 51-year-old woman with buccolingual gingival swelling having a final diagnosis of metastatic mucinous adenocarcinoma from the breast. A tissue biopsy was performed followed by immunohistochemistry that confirmed the diagnosis. They are extremely rare, making the diagnosis challenging as it may mimic a benign neoplasm. It accounts for approximately 1% of all oral malignant neoplasms having gingival propensity. The clinician should therefore take into account every diagnostic aspect while encountering such oral lesions to achieve proper patient welfare.

Preserving periodontal tissue in the treatment of a large peripheral ossifying fibroma: a case study.

Peripheral ossifying fibroma (POF) is a reactive, benign gingival enlargement. Its etiology is not fully known. It can be seen in many different sizes in the mouth. The histopathological appearance of POF is mineralized tissue and fibrous proliferation. All relevant soft and hard tissues must be removed to prevent recurrence. Periodontal tissue remaining after excision is important for tooth preservation. With large lesions, the loss of healthy periodontal tissue is also large. Periodontal surgical approaches are important to preserve the remaining periodontal tissue. The positive effects of autogenously obtained titanium-prepared platelet-rich fibrin (T-PRF) and connective tissue graft (CTG) on soft tissue are well known. A 34-year-old woman presented with a fibrous and pedunculated gingival mass in the upper left canine premolar region. The operation was performed with complete excision of the lesion down to the bone along with the surrounding healthy tissue. Periodontal treatment of the large defect created after excision of a large POF lesion was performed with laterally positioned flap, CTG and T-PRF. The periodontal tissue and defect were noted to heal in a healthy manner at the 6-month follow-up. POF is a benign lesion; however, it has a high recurrence rate. Complete elimination of the lesion is crucial to prevent recurrence. Periodontal surgical methods and biomaterials applied after surgical excision are significant to maintain the periodontal health of the remaining teeth and tissues.

[Clinical factors affecting the prognosis of lower gingival squamous cell carcinoma].

OBJECTIVE: To define the clinical factors that influence local recurrence and survival in patients with lower gingival squamous cell carcinoma (LGSCC) and determine whether bone invasion is an independent prognostic factor for them. METHODS: A total of 104 patients with LGSCC hospitalized in Peking University Stomatology Hospital from June 2013 to December 2015 were enrolled in this retrospective study.All the patients were followed-up for more than 3 years.The degree of bone invasion was assessed using preoperative imaging data (CT and panoramic radiograph).The degree of bone invasion was divi-ded into four categories: no bone invasion, invasion of cortical bone, invasion of bone marrow cavity, and invasion of the mandibular canal.According to the central position of tumor, it was divided into two types: anterior mandibular invasion (anterior region of the mental foramen) and posterior mandibular invasion (posterior region of the mental foramen). RESULTS: of different invasion depth groups were compared using Mann-Whitney U test.P value < 0.05 was considered to be statistically significant.Kaplan-Meier survival analysis method was used to draw survival curve, and COX regression was used to explore the risk ratio (HR) and 95% confidence interval (CI) of prognostic factors of LGSCC. RESULTS: The follow-up results showed that the 1-, 3-, and 5-year survival rates of LGSCC in this group were 91%, 84%, 82%, respectively.32.7%(34/104) of patients had cervical lymph node metastasis.The cervical lymph node metastasis rate of the anterior segment of the mandible was 12.5%(2/16), and 36.4%(32/88) for the posterior segment of the mandible (P < 0.05).Univariate and multivariate COX analysis showed that the N stage and local recurrence were the prognostic factors of LGSCC patients (P < 0.05). CONCLUSION: As the degree of mandibular invasion increases, the prognosis of patients with mandibular gum cancer becomes worse.N stage and local recurrence are prognostic risk factors for LGSCC.The incidence of cervical lymph node metastasis for LGSCC is related to the primary tumor location.It is concluded that tumors located at the posterior of the mandible might be more prone to cervical lymph node metastasis than the anterior of the mandible.Thus various levels of cervical lymph node dissection strategies should be adopted for different sites of LGSCC.

Angioleiomioma oral mimetizando um granuloma piogênico: relato de caso raro / Oral Angioleiomyoma mimetizing a pyogenic granuloma: A rare case report

Angioleiomioma (AL) é um tumor benigno de origem perivascular que raramente é observado na cavidade oral, principalmente em localizações como a gengiva. Devido sua apresentação clínica inespecífica, os ALs podem mimetizar outras lesões orais, como tumores benignos de glândulas salivares e lesões reacionais, como o granuloma piogênico. O presente artigo objetiva relatar um caso raro de AL localizado em gengiva, em uma paciente de 19 anos. Clinicamente, a lesão apresentava-se como um tumor assintomático, oval, pedunculado, bem definido, com superfície lisa, consistência fibrosa e cor eritematosa, semelhante a um granuloma piogênico, Uma biópsia excisional foi realizada e o fragmento foi encaminhado para análise histopatológica, que revelou uma proliferação vascular de diversos calibres, contendo paredes musculares espessas e proliferação muscular adjacente, além de infiltrado inflamatório, predominantemente crônico, hemácias extravasadas e área de ulceração, consistente com o diagnóstico de AL inflamado. A histopatologia desempenha um papel importante no diagnóstico final de lesões raras e com características clínicas inespecíficas. A excisão cirúrgica da lesão é o tratamento de escolha mais eficaz para os ALs orais. (AU)

Angioleiomyoma (AL) is a benign tumor of smooth muscle of perivascular origin that is rarely seen in the oral cavity, mainly in locations like the gingiva. Due to their nonspecific clinical presentation, ALs can mimic other oral lesions, such as benign salivary gland tumors and reactional lesions, as a pyogenic granuloma. We reported a case of an AL located in the gingiva in a 19-year-old female patient. In clinical terms, the lesion was presented as an asymptomatic, oval, pedunculated, well-defined nodule with a smooth surface, fibrous consistency and erythematous color, similar to a pyogenic granuloma. An excisional biopsy was performed and the fragment was sent for histopathological analysis that revealed a vascular proliferation of different calibers, containing thick muscle walls and adjacent muscle proliferation, in addition to an inflammatory infiltrate, predominantly chronic, extravasated red blood cells and an area of ulceration, consistent with the diagnosis of inflamed AL. The histopathology plays an important role in the final diagnosis of rare lesions and with nonspecific clinical characteristics. The surgical excision of the lesion is the most effective treatment of choice for oral ALs. (AU)

Gingival neoplasms: a multicenter collaborative study of 888 patients in Brazil

Background: To evaluate the prevalence and clinicopathological features of a large series of gingival neoplasms in Brazil. Material and methods: All gingival benign and malignant neoplasms were retrieved from the records of six Oral Pathology Services in Brazil, during a 41-year period. Clinical and demographic data, clinical diagnosis, and histopathological data were collected from the patients' clinical charts. For statistical analysis, the chi-square, median test of independent samples and the U Mann-Whitney tests were used, considering a significance of 5%. Results: From 100,026 oral lesions, 888 (0.9%) were gingival neoplasms. There were 496 (55.9%) males, with a mean age of 54.2 years. Most cases (70.3%) were malignant neoplasms. Nodules (46.2%) and ulcers (38.9%) were the most common clinical appearance for benign and malignant neoplasms, respectively. Squamous cell carcinoma (55.6%) was the most common gingival neoplasm, followed by squamous cell papilloma (19.6%). In 69 (11.1%) malignant neoplasms, the lesions were clinically considered to be inflammatory or of infectious origin. Malignant neoplasms were more common in older men, appeared with larger size, and with a time of complaint shorter than benign neoplasms (p<0.001). Conclusions: Benign and malignant tumors may appear as nodules in gingival tissue. In addition, malignant neoplasms, especially squamous cell carcinoma, should be considered in the differential diagnosis of persistent single gingival ulcers. (AU)

Gingival neoplasms: a multicenter collaborative study of 888 patients in Brazil.

BACKGROUND: To evaluate the prevalence and clinicopathological features of a large series of gingival neoplasms in Brazil. MATERIAL AND METHODS:  All gingival benign and malignant neoplasms were retrieved from the records of six Oral Pathology Services in Brazil, during a 41-year period. Clinical and demographic data, clinical diagnosis, and histopathological data were collected from the patients' clinical charts. For statistical analysis, the chi-square, median test of independent samples and the U Mann-Whitney tests were used, considering a significance of 5%. RESULTS:  From 100,026 oral lesions, 888 (0.9%) were gingival neoplasms. There were 496 (55.9%) males, with a mean age of 54.2 years. Most cases (70.3%) were malignant neoplasms. Nodules (46.2%) and ulcers (38.9%) were the most common clinical appearance for benign and malignant neoplasms, respectively. Squamous cell carcinoma (55.6%) was the most common gingival neoplasm, followed by squamous cell papilloma (19.6%). In 69 (11.1%) malignant neoplasms, the lesions were clinically considered to be inflammatory or of infectious origin. Malignant neoplasms were more common in older men, appeared with larger size, and with a time of complaint shorter than benign neoplasms (p<0.001). CONCLUSIONS:  Benign and malignant tumors may appear as nodules in gingival tissue. In addition, malignant neoplasms, especially squamous cell carcinoma, should be considered in the differential diagnosis of persistent single gingival ulcers.

A large-cohort study of 2971 cases of epulis: focusing on risk factors associated with recurrence.

BACKGROUND: To analyze the clinicopathological features of different histological subtypes of epulis, and evaluate the risk factors associated with recurrence. MATERIALS AND METHODS: A retrospective study including 2971 patients was performed. The patients' sex, age, location, size, histological subtypes, recurrence information, oral hygiene habits, periodontitis symptoms and smoking history were retrieved from the patient medical records and follow-up information. RESULTS: Among the 2971 cases, focal fibrous hyperplasia (FFH) was the most common lesion (60.92%), followed by peripheral ossifying fibroma (POF) (29.32%), pyogenic granuloma (PG) (8.08%) and peripheral giant cell granuloma (PGCG) (1.68%). The peak incidence of epulis was in the third and fourth decade of life, with a mean age of 45.55 years. Female predominance was found in all types of lesions with a female to male ratio of 1.71:1. PG had the highest recurrence rate (17.18%), followed by POF (12.98%), FFH (9.55%) and PGCG (8.82%). Histological subtypes were significantly correlated with the recurrence of epulis (P = 0.013). Regular supportive periodontal therapy (P = 0.050) had a negative correlation with recurrence, whereas symptoms of periodontitis (P < 0.001) had a positive correlation with the recurrence of epulis. CONCLUSIONS: Controlling the periodontal inflammation and regular supportive periodontal therapy might help reduce the recurrence of epulis.

Gingival and alveolar mucosal reactive hyperplastic lesions: a retrospective clinical and histological study of 996 cases.

BACKGROUND: gingival/alveolar mucosal reactive hyperplastic lesions (GRHL), including fibrous hyperplasia (FH), pyogenic granuloma (PG), peripheral ossifying fibroma (POF) and peripheral giant cell lesion (PGCL), are a common group of oral diseases. The aim of the present study was to access the frequency and distribution of the clinical and histological features of these disorders in a Brazilian population. MATERIAL AND METHODS: all specimens diagnosed as GRHL in three Oral Pathology laboratories were selected for the study. Clinical information was retrieved from the laboratory biopsy forms and hematoxylin and eosin stained histological slides were reviewed for analysis of the histological characteristics. RESULTS: final sample was composed of 996 specimens, including 463 FH (47%), 280 PG (28%), 183 POF (18%) and 70 PGCL (7%). Females were more affected by FH, PG, and POF, and most cases affected adults with mean ages ranging from 40 to 53 years. FH, PG, and POF were more common in the upper gingiva/alveolar mucosa. Most PG, POF and PGCL were pedunculated, in contrast with FH (p<0.001). PG, FH and POF were mostly red or normal mucosal in color, while PGCL were mostly red/purple (p<0.001). PGCL were larger, followed by POF, FH and PG (p<0.001). Some histological features were characteristically found in some conditions, but they were also encountered in other lesions with variable frequencies. CONCLUSIONS: Oral medicine specialists, oral pathologists and periodontists are usually the professionals in contact with patients presenting GRHL and it is of upmost relevance that they should be familiarized with their clinical and histological profile.

Immunohistochemical Characterization of Gingival Fibromas.

PURPOSE: Gingival fibromas (GFs) are fibrous lesions of the gingiva that are not well defined in the literature. They are histologically similar to peripheral ossifying fibromas (POFs), both being characterized as cellular proliferations of dense fibrous tissue, with POFs differing in that they demonstrate foci of calcification. This study aims to expand upon the immunohistochemical characterization of GFs, and to confirm their osteoblastic phenotype. METHODS: Formalin fixed, paraffin embedded GFs, POFs and fibroepithelial polyps (FEPs) of the gingiva were examined. Immunohistochemical staining was performed for special AT-rich sequence binding protein 2 (SATB2), runt-related transcription factor 2 (RUNX2), osteocalcin and alpha-smooth muscle actin (αSMA). Sections were evaluated by light microscopy and the immunohistochemical staining patterns were assigned immunoreactive scores (IRS) based on percentage of stained cells and intensity of staining. RESULTS: GFs, POFs, and FEPs of the gingiva expressed osteoblastic markers SATB2, RUNX2 and osteocalcin. GFs and POFs expressed αSMA while FEPs of the gingiva did not. GFs and POFs had similar staining patterns of SATB2, RUNX2 and αSMA. DISCUSSION: These findings demonstrate that GFs and POFs exhibit a similar immunohistochemical profile, and supports a theory that GFs are osteoblastic lesions possibly related to POFs.

Congenital granular cell epulis: 24 new cases with more differences than similarities to granular cell tumor.

Congenital granular cell epulis (CGCE) is a rare tumor of gingiva that is exclusive to newborns, has marked female predominance, and is rarely associated with other abnormalities. Although benign in behavior, CGCE can be lethal by obstruction of respiration and/or deglutition and can require a multidisciplinary team of specialist at birth for survival of an otherwise normal infant. Histologically, CGCE resembles granular cell tumor (GCT), but unlike GCT, which is Schwannian-derived, derivation of CGCE remains an enigma, largely because of its low prevalence. This study presents 24 new cases of CGCE, the largest series since the original description 150 years ago and permits detailed study of homogeneity of cases diagnosed as CGCE as well as detailed comparisons of CGCE with GCT by clinical, morphological, immunohistochemical, and ultrastructural studies. The data show homogeneity within the CGCE cases, more differences than similarities between CGCE and GCT, and no immunohistochemical staining for common placental proteins/hormones in CGCE. The findings support a primitive mesenchymal cell origin, and a progressive degenerative process in CGCE, rather than neoplasia. Prenatal detection of this lesion is important to facilitate adequate preparations for support of these infants during labor and delivery.

Peripheral ossifying fibroma: A 20-year retrospective study with focus on clinical and morphological features.

BACKGROUND: Peripheral Ossifying Fibroma (POF) is a reactive hyperplastic lesion that exclusively occurs in the gingiva and is characterized by the deposition of dystrophic calcification, cementum-like tissue, and immature and mature bone within the connective tissue. The objective of the present study was to perform a retrospective analysis of clinicopathologic features of POF. MATERIAL AND METHODS: Clinical and histopathological data were obtained from biopsy records and histopathological reports from a Brazilian reference service in Oral Pathology (1999 - 2020). Morphological analysis was performed to evaluate features related to the mesenchymal component, inflammatory infiltrate, ulceration, and mineralized tissue. RESULTS: A total of 270 POFs were diagnosed during the study period. A higher frequency was observed in females (71.9%) between the third (22.9%) and fourth (23.3%) decades of life. The anterior upper gingiva (29.1%) was the most affected region. Mature (86.7%) and immature (52.6%) bone tissue were the most frequent. There was a significant association between immature bone deposition and lesions with size ≤ 1.7 cm (p = 0.041); immature bone and cement-like tissue deposition with an evolution time ≤ 16 months (p < 0.001); deposition of immature bone and mesenchymal hypercellularization (p < 0.001); deposition of dystrophic calcification and the presence of ulceration (p < 0.001). CONCLUSIONS: The clinical characteristics corroborate the findings in the literature. The heterogeneous distribution and quantity of mineralized tissues found in the analyzed cases support the theory that the different mineralized tissues constitute a spectrum of clinical maturation of POF.

Épulis congénito: reporte de un caso clínico / Congenital epulis: clinical case study / Epúlide congênita: relato de caso clínico

El épulis congénito es una patología neonatal muy rara. Se trata de un tumor benigno pediculado de la mucosa de los maxilares, más frecuentemente localizado en maxilar superior en relación 2-3/1. Se describe el caso de un recién nacido de sexo femenino, de término, adecuado, vigoroso. Se constata al nacimiento la presencia de un épulis congénito que causa alteraciones de la succión. Se realiza intervención quirúrgica temprana, con resolución de la patología sin complicaciones.

Congenital epulis is a very rare neonatal pathology. It is a benign pedunculated tumor of the jaw mucosa, most frequently located in the upper jaw in a 2-3 / 1 ratio. The case of a newborn, female, term, adequate, vigorous is described. Noting at birth a congenital Epulis that causes suction alterations. Early surgical intervention is perfomed with resolution of the pathology without complications.

A epúlide congênita é uma patologia neonatal muito rara. É um tumor pedunculado benigno da mucosa dos maxilares, mais frequentemente localizado no maxilar superior na proporção de 2-3/1. Descreve-se o caso de um recém-nascido, do sexo feminino, a termo, adequado, vigoroso. Verificando ao nascimento uma Epúlide congênita que causa alterações na sucção. A intervenção cirúrgica precoce é realizada com resolução da patologia sem complicações.

Large Congenital Epulis: A Neonatal Tumour with Striking Appearance, but Simple Management.

Background Congenital epulis is a benign tumor of upper gingiva. Larger lesions interfere with mouth closing and normal feeding and may obstruct airways. We present a neonate with a large epulis. Case Report: A full term 3 kg 5 days female baby had a 20 cm × 15 cm gingival mass protruding from the oral cavity, connected by a pedicle attached to right upper gingiva (Figure 1). Multiple trophic ulcers had developed in the mass after birth. Mouth closing and normal feeding were hampered. The mass was excised surgically and baby improved. Conclusion: A large congenital epulis, though worrisome to parents, can be satisfactorily managed by surgical excision and has a good prognosis.

Prognostic factors for lymph node metastasis from upper gingival carcinomas.

OBJECTIVES: This study sought to identify tumor characteristics that associate with regional lymph node metastases in squamous cell carcinomas originating in the upper gingiva. MATERIALS AND METHODS: Data from 113 patients from Osaka University Dental Hospital were included. We measured each primary tumor's width, length, depth, and the extent of bone invasion. Additionally, tumor signal intensity for T1 and T2-weighted images as well as the center of the tumor's location and T classification was assessed, and a histopathological analysis was performed. RESULTS: Tumor signal intensity was not found to be a significant prognostic factor. However, bucco-lingual width, histopathological classification as well as the tumor's location were significantly different between metastatic and non-metastatic groups in both univariate and multivariate analysis. Superior-inferior depth and T classification were significant only in the univariate (and not the multivariate) analysis. CONCLUSIONS: Bucco-lingual width, histopathological grading as well as the tumor's location are likely to be important predictors for the occurrence of LN metastasis in upper gingival carcinoma patients and should be considered when managing care for these patients.

Primary malignant melanoma of mandibular gingiva: A rare case report.

Oral malignant melanomas are rare neoplasms of the oral cavity which present significant diagnostic ambiguity. The etiology is unclear though the stimulation of melanoblasts by genetic, epigenetic, and traumatic causes that have been proposed in etiopathogenesis. Clinically, it presents as a pigmented swelling or growth which remains asymptomatic until it advances to later stages. It is highly invasive and metastasizes quickly; hence, it has a very poor prognosis with a survival rate of only 7%. Early diagnosis of the neoplasm and thorough investigation is not only necessary for prompt treatment but also necessary for a favorable prognosis.

Nomograms for Predicting Cancer-Specific Survival of Patients with Gingiva Squamous Cell Carcinoma: A Population-Based Study.

OBJECTIVE: The use of the traditional American Joint Committee on Cancer (AJCC) staging system alone has limitations in predicting the survival of gingiva squamous cell carcinoma (GSCC) patients. We aimed to establish a comprehensive prognostic nomogram with a prognostic value similar to the AJCC system. METHODS: Patients were identified from SEER database. Variables were selected by a backward stepwise selection method in a Cox regression model. A nomogram was used to predict cancer-specific survival rates for 3, 5 and 10 years in patients with GSCC. Several basic features of model validation were used to evaluate the performance of the survival model: consistency index (C-index), receiver operating characteristic (ROC) curve, calibration chart, net weight classification improvement (NRI), comprehensive discriminant improvement (IDI) and decision curve analysis (DCA). RESULTS: Multivariate analyses revealed that age, race, marital status, insurance, AJCC stage, pathology grade and surgery were risk factors for survival. In particular, the C-index, the area under the ROC curve (AUC) and the calibration plots showed good performance of the nomogram. Compared to the AJCC system, NRI and IDI showed that the nomogram has improved performance. Finally, the nomogram's 3-year and 5-year and 10-year DCA curves yield net benefits higher than traditional AJCC, whether training set or a validation set. CONCLUSION: We developed and validated the first GSCC prognosis nomogram, which has a better prognostic value than the separate AJCC staging system. Overall, the nomogram of this study is a valuable tool for clinical practice to consult patients and understand their risk for the next 3, 5 and 10 years.

Basaloid squamous cell carcinoma in the maxillary gingiva.

Basaloid squamous cell carcinoma (BSCC) is a rare, unique, and aggressive variant of squamous cell carcinoma which mostly occurs in the upper aerodigestive tract. Histologically and immunologically different from conventional squamous cell carcinoma, it is mostly seen in men of the sixth and seventh decades and is commonly associated with tobacco and alcohol usage. BSCC usually presents as a high stage disease with distant metastasis, high recurrence rate, and poor prognosis. In the head-and-neck region, BSCC has a strong predilection for sites such as the base of the tongue, soft palate, and epiglottis. Less commonly, it may also occur on the floor of the mouth, gingiva, and tonsils. In the present article, we report a case of BSCC in the right maxillary anterior gingiva of a 57-year-old female for its rarity.

The natural product lapiferin inhibits cell proliferation and promotes cell apoptosis in gingival squamous cell carcinoma via P21 regulation.

Gingival squamous cell carcinoma (GSCC) is responsible fora large proportion of oral cavity malignancies. GSCC is characterized by rapid cell growth, and progressive invasion and migration. P21 is a widely recognized tumor suppressor, which is induced by P53 activation; however, drugs that aim to promote P21­mediated tumor suppression remain to be identified. A natural compound library was used to perform broad­spectrum screening of drugs that could promote P21 expression. Subsequently, the effects of the screened drug on GSCC cell proliferation and apoptosis were evaluated. The results of the present study suggested that lapiferin was the most effective natural compound that promoted the expression of P21 at both mRNA and protein levels. Lapiferin inhibited proliferation and enhanced apoptosis of YD­38 GSCC cells in a dose­dependent manner. Furthermore, following treatment with lapiferin, the critical cell cycle regulators cell division cycle 25C and cyclin B1 and tumor cell proliferation markers proliferating cell nuclear antigen and Ki67 were markedly decreased. In addition, pro­apoptotic proteins were promoted following treatment of YD­38 cells with lapiferin. Following the depletion ofP21 expression, lapiferin­mediated inhibition of cell proliferation and enhancement of cell apoptosis were significantly reduced. These results indicated that lapiferin may exert potent antitumor effects on GSCC via regulation of P21; therefore, lapiferin may be considered a potential, natural therapeutic agent for the treatment of GSCC.

A canine case of malignant melanoma carrying a KIT c.1725_1733del mutation treated with toceranib: a case report and in vitro analysis.

BACKGROUND: Canine malignant melanoma is highly aggressive and generally chemoresistant. Toceranib is a kinase inhibitor drug that inhibits several tyrosine kinases including the proto-oncogene receptor tyrosine kinase KIT. Although canine malignant melanoma cells often express KIT, a therapeutic effect for toceranib has yet to be reported for this tumor, with only a small number of patients studied to date. This is a case report of a dog with malignant melanoma that experienced a transient response to toceranib. Furthermore, the KIT expressed in the tumor of this case was examined using molecular analysis. CASE PRESENTATION: A Shiba Inu dog presented with a gingival malignant melanoma extending into surrounding structures with metastasis to a submandibular lymph node. The dog was treated with toceranib (Palladia®; 2.6-2.9 mg/kg, orally, every other day) alone. Improvement of tumor-associated clinical signs (e.g., halitosis, tumor hemorrhage, trismus, and facial edema) with reduced size of the metastatic lymph node was observed on Day 15. The gingival tumor and associated masses in the masseter and pterygoid muscles decreased in size by Day 29 of treatment. Toceranib treatment was terminated on Day 43 due to disease progression and the dog died on Day 54. The tumor of this dog had a novel deletion mutation c.1725_1733del within KIT and the mutation caused ligand-independent phosphorylation of KIT, which was suppressed by toceranib. This mutation was considered to be an oncogenic driver mutation in the tumor of this dog, thereby explaining the anti-tumor activity of toceranib. CONCLUSIONS: This is the first report that presents a canine case of malignant melanoma that responded to toceranib therapy. KIT encoded by KIT harboring a mutation c.1725_1733del is a potential therapeutic target for toceranib in canine malignant melanoma. Further investigation of the KIT mutation status and toceranib therapy in canine malignant melanoma will need to be undertaken.