rhabdomyosarcoma is a malignant neoplasm derived from primitive mesenchyme that retains the capacity for skeletal muscle differentiation and thus often arises at sites where skeletal muscle tissue is normally absent ( e.g. urinary bladder ) , or in areas where striated muscle is scanty ( e.g. nasal cavity and middle ear ) . the most common site is head and neck ( parameningeal and orbit ) , followed by genitourinary tract . less commonly involved sites of head and neck regions are nasal cavity and nasopharynx , ear , paranasal sinuses , soft tissue of face and neck and finally the oral cavity , including the tongue lip and palate . it mostly affects children below 10 years of age but may also affect adolescents and young adults . in the present case , only 17 cases have been reported in the indexed journals till date involving intraoral mucosa according to our review of the literature . intraoral site involvement in a patient nearer to adult age is extremely rare , and the manner by which panel of immunohistochemical markers had been used to confirm the diagnosis makes this case unique . a 17-year - old female patient reported to the department of oral pathology with a mass involving the left side of the mouth for the last 1 months . the lesion was stated to be fast enlarging , painless and caused occasional spontaneous bleeding . left middle third of the face showed slight swelling . on intraoral examination , a diffuse fleshy mass was seen involving left posterolateral part of the palate , left upper retromolar region and adjacent buccal mucosa , measuring about 3 cm  3 cm [ figure 1 ] . on palpation , the lesion was firm , mildly tender and seemed to be extending inferiorly , laterally as well as medially . orthopantomogram showed no bony abnormality except faint soft tissue shadow behind maxillary second molar and impacted left maxillary canine . contrast - enhanced computed tomography showed soft tissue lesion in the parapharyngeal space both causing mass effect on oropharynx and nasopharynx with extension to the cheek causing erosion of mandible [ figure 2 ] . incisional biopsy was taken from the lesion after having written informed consent of her parents . underlying connective tissue contained the tumor mass consisting of clusters of primitive spindle and round cells with dark staining nuclei and little cytoplasm arranged in abundant myxoid stroma [ figure 3 ] . mitotic figures and typical tadpole nuclei were also present [ figure 5 ] , but characteristic cross striation was not found . in other areas , primitive oval cells and scanty rhabdomyoblasts with eccentric vesicular nuclei the lesion was further provisionally diagnosed as malignant round cell tumor compatible with embryonal rhabdomyosarcoma . for confirmation of diagnosis , diffuse swelling involving left maxillary tuberosity , adjacent part of palate and buccal mucosa contrast - enhanced computed tomography shows space occupying lesion involving oropharynx , nasopharynx , parapharyngeal space with extension to the cheek and mandible round and spindle - shaped tumor cells with hyperchromatic nuclei and little cytoplasm.(h&e stain , 100 ) tumor cell invasion into blood vessel ( h&e stain , 200 ) tumor cells with tadpole nuclei ( h&e stain , 1000 ) neoplastic rhabdomyoblast cell ( h&e stain , 1000 ) the lesion showed positive reactivity with desmin [ figure 7 ] , myod1 [ figure 8 ] , myogenin [ figure 9 ] and muscle - specific actin [ figure 10 ] . it also showed negative reactivity with cytokeratin , epithelial membrane antigen , mic-2 , synaptophysin , cd34 , cd31 and littoral cell angioma . immunohistochemical staining for desmin shows positive result ( ihc stain , 400 ) immunohistochemical staining for myod1 shows focal positive result ( ihc stain , 400 ) immunohistochemical staining for myogenin shows positive result ( ihc stain , 400 ) immunohistochemical staining for muscle - specific actin shows positive result ( ihc stain , 400 ) immunohistochemical reports of this case are given in table 1 for better understanding . according to the available case reports , it is found that mandibular gingiva is more commonly affected than maxillary gingiva . few reports of intraosseous involvement are there , one of which involved angle of the mandible and ascending ramus . palatal lesions mostly involve the soft palate , and few of them involved the uvula . this malignancy is most prevalent in the first and second decades of life , gradually decreases with increasing age and rarely affects a person in seventh or eighth decade of life . findings from table 1 helped us to confirm the diagnosis as a case of rhabdomyosarcoma . the histopathological report was of round cell tumor , and so , we had to exclude all other round cell malignancies . considering the histopathological pattern and age of the patient , we arrived at the final diagnosis of embryonal rhabdomyosarcoma . histopathological ( h / p ) diagnosis always must be confirmed by immunohistochemical investigation as the histological pattern is variable and poorly differentiated tumors bear resemblance with many other round cell malignancies . prognosis of the lesion depends on age of the patient , anatomic site , clinical staging ( tumor size , node involvement and metastasis ) and h / p subtype . twenty percent of patients develop metastasis at the time of diagnosis ; and lung , lymph node and bone marrow are the common sites . rhabdomyosarcoma is treated by complete resection of the lesion , followed by multi - agent chemotherapy with or without radiotherapy .
rhabdomyosarcoma is the malignant neoplasm of striated muscle and a relatively uncommon tumor of the oral cavity . 
 embryonal variety is the most common subtype , observed in children below 10 years of age but occasionally seen in adolescents and young adults . 
 the present report describes a case of embryonal rhabdomyosarcoma in the left posterior buccal mucosa , with extension in the adjacent alveolus , soft palate , oropharynx and nasopharynx of a 17-year - old female .