tum or consisted of a firm , well - circumscribed , ovoid piece of soft pink tissue measuring 21.51 cm in the supraglottic area of the larynx .
histologically , the mass showed a fibrous and chondromyxoid stroma containing epithelial and myoepithelial cells .
epithelial component consisted of relatively uniform - appearing cells arranged in tubules and small , nested aggregates ( figure 1 )
myoepithelial component was positive for p63 , s100 protein ( figure 2a ) , and glial fibrillary acidic protein ( gfap ) ( figure 2b ) ; and focally positive smooth muscle actin ( sma ) .
( a - b ) hematoxylin and eosin ( h&e ) stained section showing sheets of myoepithelial cells and ductular structures lined with epithelial cells set in chondromyxoid stroma ( h&e , a : 40 ; b : 100 ) .
( c ) adjacent to the lesion , normal laryngeal cartilage can be seen ( h&e , 100 ) .
immunohistochemistry indicates that the myoepithelial cells cytoplasm is focally positive for s100 protein ( a ) and glial fibrillary acidic protein ( gfap ) ( b ) ( a : 100 ; b : 100 ) .
pa is a commonly diagnosed benign tumor in the salivary glands that may also occur in a variety of other sites ; however , it is rarely seen in the larynx .
the diagnosis of pa is simple , but when it grows in an unusual site like the larynx , it can be mistaken for a malignant neoplasm .
pleomorphic adenomas are characterized by epithelial tissue mixed with tissues of myxoid , mucoid or chondroid appearance .
histologically , pleomorphic adenoma of the larynx may resemble aggressive epithelial tumors because of the high cellularity and lack of a stromal component .
importantly , this feature is not in keeping with that of major salivary glands , which demonstrate relatively reduced myoepithelial cellularity .
occasionally , pleomorphic adenomas are composed almost entirely of epithelial cells with few or no stromata
myoepithelial cells are variably positive for s100 protein , sma , gfap , calponin , and cd10 .
although pa is a benign tumor , it can cause problems in clinical management due to its tendency to recur and risk of malignant transformation .
histological features indicative of malignant transformation include cytological atypia , increased mitotic figures , satellite tumor nodules , tumor necrosis , and infiltrative margins7 .
pas have tendency to recur when not widely excised , particularly if they are predominantly mucoid , and have variability in the thickness of the capsule and the tumor invading the capsule . in addition , due to low biological requirements , the neoplastic cells can survive when spilt into the operative sites .
pas should be differentially diagnosed from other tumors such as carcinoma ex pleomorphic adenoma , adenoid cystic carcinoma , basal cell carcinoma , basal cell adenoma , myoepithelioma , polymorphous low - grade adenocarcinoma , angiofibroma , hamartoma , epidermoid cyst , hemangioma , vascular malformations , nasopharyngeal carcinoma , and nonepithelial tumors .
carcinoma ex pleomorphic adenoma exhibits extensively infiltrative malignancy with necrosis , perineurial invasion , frequent mitotic figures , marked nuclear atypia .
adenoid cystic carcinoma usually shows cribriform , solid or tubular pattern similar to cylindromas of the skin .
it is composed of small , bland myoepithelial cells with scant cytoplasm and dark , compact , angular nuclei that surround pseudoglandular spaces with periodic - acid schiff ( pas)-positive excess basement membrane material and mucin .
peripheral perineurial invasion and small , true , glandular lumina are sometimes seen , but no squamous differentiation , and extensive necrosis is usually absent .
adenoid cystic carcinoma has high proliferative index , high p53 immunoreactivity , and intense staining for b - cell lymphoma 2 ( bcl 2 ) , but negative reactivity for glial fibrillary acidic protein .
in contrast , pleomorphic adenoma is not invasive , shows no perineurial invasion and has squamous metaplasia and mesenchyme - like areas .
it is an infiltrative tumor with perineurial invasion and vascular invasion as well as variable cytologic atypia and mitotic activity .
it is composed of solid , trabecular , tubular or membranous patterns , but no myxoid matrix or cartilagenous areas .
basal cell adenoma is composed of basaloid cells sharply delineated from the stroma by basement membrane .
polymorphous low - grade adenocarcinoma is usually a nonencapsulated tumor with diverse ( polymorphous ) growth patterns , infiltrative borders , perineurial invasion and tumor necrosis is rare .
differential diagnosis of pa consists of myoepithelioma , a benign epithelial salivary gland tumor , and presence of plasmacytoid or spindled myoepithelial cells .
additionally , basal cell adenoma may also be involved in the differential diagnosis . to conclude , pleomorphic adenoma of the larynx is a rare neoplasm and therefore its diagnosis requires a high index of suspicion .
recurrence many years after surgical excision as well as malignant transformation should be a concern and therefore long - term follow - up is necessary .
 pleomorphic adenoma ( pa ) is the most common benign neoplasm of the salivary glands . 
 it usually occurs in major salivary glands , such as the parotid and submandibular glands . 
 occasionally , however , it occurs in the larynx . 
 these lesions generally present as a slow - growing , painless mass . 
 malignant transformation is very rare , but it increases with time . the present report is the case of a 59-year - old male who presented with a complaint of hoarseness . 
 right vertical partial hemilaryngectomy revealed an intact , mucosa - covered , fleshy 21.51 cm mass in the supraglottic area of the larynx . 
 lesion had histological characteristics of a pa , and this was confirmed by immunohistochemical expression of cytokeratin , s100 protein , glial fibrillary acidic protein ( gfap ) and vimentin . 
 their histopathological identification is , however , not always straightforward ; immunohistochemistry can contribute significantly to formulation of a definitive diagnosis and to the realization of appropriate follow - up . 
CASE REPORT
DISCUSSION