squamous cell carcinoma ( scc ) is the most common malignant mucosal neoplasm to affect the head and neck region . occasionally , variants of scc may be encountered , which includes verrucous , exophytic or papillary , spindle cell ( sarcomatoid ) , basaloid and adenosquamous types that make up an aggregate of 10%15% of all sccs . spindle cell carcinoma ( spcc ) is a relatively rare malignancy affecting the upper aerodigestive tract comprising up to 3% of scc . the most common site of origin in the head and neck region is larynx and hypopharynx . spcc , also called lane tumor , pseudosarcoma , carcinosarcoma , sarcomatoid carcinoma , collision tumor and pleomorphic carcinoma , is an uncommon poorly differentiated type of scc . it is a biphasic tumor with a carcinoma that has surface epithelial changes and an underlying spindle - shaped neoplastic proliferation . there has been confusion over the basic nature of the sarcomatoid element , that is , whether it is benign or malignant and mesenchymal or epithelial in origin . the epithelial nature of the sarcomatoid component of spcc is clearly revealed by a combination of immunohistochemical staining for keratins and electron microscopic demonstration of tonofilament - like filaments and/or desmosome - like structures . however , who classification of tumor has placed this entity under malignant epithelial tumors of scc . moreover , to the best of our knowledge , there is only one case report in literature documenting the malignant transformation of oral verrucous leukoplakia into spcc . we report here a case of spcc arising in the buccal mucosa in a patient who was previously diagnosed with oral leukoplakia and was under medical management for same . a 35-year - old female patient reported to the outpatient department of oral medicine and radiology with the chief complaint of pain in the left cheek for past 8 days . according to history of presenting illness , the patient was provisionally diagnosed as homogenous leukoplakia with respect to left buccal mucosa 6 months back [ figure 1 ] . at that time , an incisional biopsy was done from left buccal mucosa which was suggestive of hyperkeratosis . the patient was then prescribed antioxidant once daily and was advised to report for regular follow - up . after 6 months , she reported with the chief complaint of pain in the left buccal mucosa past 8 days . personal history showed that she had history of areca nut chewing , 23 times in a day for 67 months and had quit the habit 4 years back . extraoral examination showed the presence of left submandibular lymphadenopathy which was tender and fixed to the underlying soft tissues . intraoral hard tissue examination showed grossly decayed 18 , root stumps of 14 , 46 , 47 and 48 , carious 13 , 14 , 23 and 35 and missing 27 , 36 and 37 . intraoral soft - tissue examination revealed diffuse , thick , nonscrapable white patch on the left buccal mucosa extending from commissure region up to the retromolar region anteroposteriorly and from the level of the occlusal plane to buccal vestibule superoinferiorly [ figure 2 ] . a punched out ulcer was seen on the left buccal mucosa approximately 1 cm  1 cm in size located 1 cm lateral to the commissure of mouth [ figure 2 ] . on palpation , it was well defined with indurated margins and covered with a yellowish base . based on history and examination findings , provisional diagnosis of homogenous leukoplakia with malignancy in relation to left buccal mucosa was made . the patient was advised to get routine blood investigation and contrast - enhanced computed tomography ( cect ) scan of the head and neck . clinical photograph showing homogenous leukoplakia on the left buccal mucosa before appearance of ulcer clinical photograph of the patient showing homogenous leukoplakia with an ulcer after 6 months of initial lesion cect revealed heterogeneously enhancing soft - tissue thickening in the left buccal space with cervical lymphadenopathy involving level ib and bilateral upper jugular nodes [ figure 3 ] . histopathological sections showed hyperparakeratinized stratified squamous dysplastic epithelium with a focal area of invasion in the underlying connective tissue [ figure 4 ] . the lesional tissue was composed of streaming fascicles of anaplastic spindle cells [ figure 5 ] , which showed marked pleomorphism and strong resemblance to atypical mesenchymal cells . the cells present in the fasciculated pattern were elongated with elliptical nuclei and showed hyperchromatism and altered nuclear - cytoplasmic ratio [ figure 6 ] . numerous mitotic figures and abnormal mitoses were seen throughout the lesional tissue . in the deeper layer , spindle cells had invaded the muscle tissue and had caused degenerative changes in the muscle fibers . sections showed that 90% of the tumor cells were positive for pancytokeratin [ figure 7 ] and 5% of the tumor cells were positive for vimentin [ figure 8 ] . the patient was referred to the department of oral and maxillofacial surgery where it was planned to carry out surgical excision with wide margins along with neck dissection . contrast - enhanced computed tomography section showing enhanced and enlarged bilateral cervical lymph nodes ( arrow ) photomicrograph ( 10 ) showing dysplastic epithelium with focal area of invasion in underlying connective tissue photomicrograph ( 10 ) showing streaming fascicles of anaplastic spindle cells ( arrow ) photomicrograph ( 40 ) showing marked pleomorphism and strong resemblance to atypical mesenchymal cells with hyperchromatism and altered nuclear - cytoplasmic ratio photomicrograph ( 10 ) showing positive immunohistochemical expression for pancytokeratin in majority of tumor cells and inset ( 40 ) showing cytoplasmic positivity for pancytokeratin ( arrow ) photomicrograph ( 10 ) showing positive immunohistochemical expression for vimentin in very few tumor cells and inset ( 40 ) showing cytoplasmic positivity for vimentin they are relatively uncommon in the oral cavity accounting for < 1% of all tumors in this region . spcc is a rare variant of scc with both malignant squamous cells and spindle cells of epithelial origin . moreover , the diagnosis can be challenging , especially when scc component is not obvious . thus , to establish a correct diagnosis , any clue of epithelial component should be carefully sought in suspected lesions . four factors are considered as predisposing factors , namely , tobacco , alcohol , poor oral hygiene and previous irradiation to area of tumor . it commonly affects men than women , usually in the middle or later decades of life with a mean age of 57 years . in the present case , the patient is a female in the third decade of life . although the patient did not have any previous history of irradiation , there was known history of areca nut chewing . clinical presentation of oral spcc can vary from an exophytic polypoid mass with an ulcerated surface to a frankly infiltrative ulcer , frequently affecting lower lip , tongue and alveolar ridge . in the present case , the patient presented with leukoplakia which had transformed into ulcer over a period of 6 months on buccal mucosa , rare site of presentation . histologically , it is characterized by the presence of two distinct epithelial - derived components : a carcinomatous or scc component and a sarcomatoid or dysplastic spindle cell component . the carcinomatous component comprises a minor portion of the tumor mass and is represented by dysplasia , carcinoma in situ or frankly invasive carcinoma . areas of squamous differentiation are most consistently identified at the base of polypoid lesion at advancing margin or within invaginations at the surface where epithelium is not ulcerated or denuded . the spindle cell component comprises major portion of this tumor and imitates a number of different mesenchymal processes . it can be arranged in diverse array of appearance : storiform , cartwheel or whorled : resembling a malignant fibrous histiocytoma ; interlacing bundles or fascicles similar to leiomyosarcoma or malignant peripheral nerve sheath tumor ; chevron or herringbone similar to fibrosarcoma . in the present case , areas of elongation and spindling seem to arise from basal epithelial cells , making demarcation between surface epithelial cells and underlying tumor indistinct . the epithelial and spindle components share a common pathway of tumorigenesis despite their divergence at the phenotypic level . however , through positive keratin immunostaining and demonstration of desmosomes and tonofilaments in the cells , it has been proven that spindle cell elements are epithelial in origin . immunohistochemically , the most sensitive and reliable epithelial markers to be used are keratin and epithelial membrane antigen . these findings suggest that these cells have acquired mesenchymal properties both morphologically and functionally through metaplastic changes . double labeling with keratin and vimentin reflects the versatility of intermediate filament phenotype . in the present case spcc in the oral cavity and oropharynx is potentially aggressive and seems to recur easily and tends to metastasize . although it is difficult to predict biologic behavior , those with deeply invasive tumors tend to have a poor prognosis , whereas those with early stage tumors usually have an excellent prognosis . it is common for potentially malignant disorders such as leukoplakia to undergo malignant transformation into scc but is rare to transform into spcc , a variant of scc . spcc is a biphasic malignant tumor which is aggressive in nature , tends to recur easily and metastasize . interesting part of this tumor is that it mimics other connective tissue sarcoma and malignancy at microscopic level , so its histopathologic differentiation is a must for timely diagnosis and management .