rhabdomyomas ( rms ) are rare lesions of striated muscle origin that can be found in cardiac and in extracardiac locations . of these two , in the head and neck , the adult type is more common . laryngeal rms are extremely rare , with only 40 cases being reported worldwide.1 adult - type rms show an absolutely benign behavior and never metastasize.2 the treatment is excision . histologically , these tumors are subcategorized into adult and fetal forms according to their degree of cellular differentiation and maturity . adult - type tumors are confined to the head and neck region and usually originate from musculature of the pharynx , oral cavity , or less commonly the larynx . the reported ages of affected patients have ranged from 16 to 76 years.3 most reported cases of extracardiac rm have involved solitary masses . approximately 3 to 10% of adult rms may be multiple.4 rm virtually has no malignant potential . they frequently are asymptomatic solitary lesions but progressive hoarseness , a foreign - body sensation , and airway obstruction may occur . the radiologic features are usually those typical of benign neoplasms , with well - circumscribed margins with no invasion of surrounding tissue.1 in a few cases , computed tomography ( ct ) findings may mimic the appearance of the malignant lesions with indistinct borders and blending with adjacent isodense muscle tissue . the differential diagnosis for laryngeal masses includes cysts , laryngoceles , malignant neoplasms such as squamous cell carcinoma and rhabdomyosarcoma , as well as benign neoplasms such as hemangiomas , lipomas , amyloidomas , neurofibromas , and granular cell tumors.5 
  histologic analysis is essential for diagnosis . adult rm have been confused with many other benign tumors as hibernoma , oncocytoma , tumor of salivary glands , paraganglioma , and others,6 but mainly with granular cell tumor.1 microscopically the adult rm is characterized by large , closely packed , elongated to polygonal cells with pink to bright eosinophilic and finely granular cytoplasm . the nuclei are round to oval , vesicular , usually peripherally located , but may be centrally located . cross - striations are characteristic but are not an obligatory feature in light microscopic evaluation.2 they are more easily seen with phosphotungstic acid hematoxylin staining . the diagnosis of rm is histopathologic and can generally be well defined , but some cases can cause difficulties . the ihc features of rm are identical to those of normal skeletal muscle cells because it shows positivity to msa ( muscle - specific actin ) , desmin , and myoglobin.6 the positivity of these muscular markers is consistent with rm , as well as the positivity for vimentin , a marker of mesenchymal tissues.2 the main lesion to be differentiated from rm is the granular cell tumor that morphologically consists mainly of smaller cells , has no cross - striations , and is consistently positive for s-100 protein but negative for all myogenous markers ihc preparations.2 
  rm treatment is surgical resection . the 35-year - old white man complained of progressive hoarseness during a 1-year period . on indirect examination of the larynx , a large submucosal mass was noted in the left supra glottic larynx ( fig . 1 ) . the contrast - enhanced ct of the neck revealed a well - demarcated diffusely hyperattenuating submucosal mass on the left supraglottic space ( fig . 2 ) . 
 the laryngeal bulky lesion . 
 computed tomography revealed a well - demarcated diffusely hyperattenuating submucosal mass . markers for epithelium membrane tumors and s-100 protein for neuroectoderm tumors were negative , thus changing the diagnosis to rm adult type . at a careful revision of the slides , the hematoxylin and eosin sections revealed neoplastic closely packed polygonal cells with deeply eosinophilic vacuolated cytoplasm ( fig . cross - striations , not noted before , were present in few cells ( fig . 5 ) . ( hematoxylin and eosin ,   400 . ) 
 scarcely seen cross - striations . certainly the adult - type rm of the larynx is an extremely rare benign tumor of myoblastic origin . a literature review allows us to say that only 40 well - documented cases have been reported until today worldwide . in the past , this confusion is due to granular eosinophilic cytoplasm that is common to both diagnoses , although they have a completely different histogenesis . another important observation of the histologic point of view is that the rm should not be confused with rhabdomyosarcoma , which has a completely different prognosis . the histologic diagnosis should be no problem if adequately prepared slides are available , but as these tumors are very rare and many pathologists are not familiar with this type of tumor , there are reports of substantial difficulties to diagnose them on the first try . we present another case of laryngeal rm in a patient whose diagnosis was not initially set . although the clinical and pathologic findings should be taken into consideration , we emphasize that ihc plays an important role in the differential diagnosis . symptoms of laryngeal rm do not differ from those caused by other benign tumors of the larynx , but one should keep in mind the possibility of local airway obstruction when the patient complains of breathing difficulties . the tumor is usually described as a submucosal mass with a smooth surface that can resemble the appearance of a cyst . laryngoscopy and imaging exams help locate and define the limits of the tumor , but the definitive diagnosis will always depend on the histopathologic studies . the clinical outcome of laryngeal rm adult type is benign and no evidence of metastasis was reported in the literature . treatment should always be surgical removal , via either endoscopic or external approach , but always preserving the adjacent structures such as the vocal folds and the swallowing apparatus . although muscle tumors of the larynx are very rare , the rm should be considered when there is a submucosal mass in the larynx . because the establishment of definitive diagnosis can be difficult with routine histopathology , it is important to consider the realization of ihc studies .
introduction  rhabdomyoma is a rare benign tumor derived from skeletal muscles . 
 laryngeal rhabdomyomas are even rarer , with only approximately 40 reported cases in world literature . 
 laryngeal rhabdomyomas usually are seen as masses covered by mucosa . 
 they are often solitary asymptomatic tumors , but symptoms such as hoarseness can occur . 
 the radiologic features are usually those typical of benign neoplasms , showing well - delineated borders . 
 the differential diagnoses for laryngeal masses include cysts , laryngoceles , and benign and malignant neoplasms . the diagnosis is usually made using histopathologic findings , but in some cases some difficulties can be found . 
 immunohistochemical staining is of great value in the differentiation of similar tumors . 
 treatment of rhabdomyoma is surgical excision . 
 objective  to describe a case of rhabdomyoma of the larynx attended at santa casa de misericrdia do rio de janeiro . 
 case report  a 35-year - old man presented with progressive hoarseness in the preceding year . 
 laryngoscopy showed a large submucosal tumor at the supraglottic region of the larynx . 
 the neck computed tomography scan confirmed the submucosal mass , with distinct borders . 
 the patient was taken to the operating suite , where endoscopic extirpation of the mass was performed . 
 initial histologic diagnosis was suggestive of paraganglioma , which was not confirmed by studies with immunohistochemical markers , and diagnosis was changed to adult - type rhabdomyoma . 
 the patient recovered well . 
 his voice returned to normal after 3 months . 
 discussion  although muscle tumors of the larynx are very rare , rhabdomyoma should be considered when there is a submucosal mass in the larynx .