MRI appearance of malignant melanoma in the sinonasal tract and nasopharynx

Abstract

Objective To investigate the MRI appearance of malignant melanoma in the sinonasal tract and nasopharynx.Methods MRI Findings and clinical data from 8 patients with biopsy or operation proved malignant melanoma were retrospectively reviewed.Gadolinium-enhanced imaging and dynamic contrast enhancement scanning were performed in all cases.Results The majority of lesions were located in the nasopharynx (n =2),middle turbinate (n =1 ),or a combination of the nasal cavity,ethmoidal sinus,and maxillary sinus ( n =5 ).The aggressive nature of the tumors was demonstrated by bone destruction ( n =5 ) and invasion of adjacent structures,involving anterior fossa (n =2 ),orbits (n =4 ),infratemporal fossa ( n =2 ),pterygopalatine fossa ( n =3 ),and parapharyngeal space ( n =1 ).The MRI appearance included two patterns.In the first pattern,the tumors were round and small (smaller than 2 cm in maximum dimension in three patients).MR signal intensity of the lesions was hyperintense to gray matter on T1 WI and hypointense on T2.In the second pattern,the lesions were irregular and large ( larger than 3 cm in maximum dimension in five patients).They showed heterogeneous low-signal on T1 WI.On T2WI,one lesion showed isointensity or little hypo-intensity,and four lesions showed hyperintense.They demonstrated mild heterogeneous enhancement on gadolinium-enhanced images.Four patients demonstrated as plateau type time-signal intensity curve (TIC) pattern,and another four patients demonstrated as wash-out type TIC pattern.Conclusions The MR signal characteristic of the malignant melanoma in the sinonasal tract and nasopharynx were related with the tumor size.When the lesion was small,the MR signal intensity was more typical.When the lesion was large,they had mixed signal intensity as other malignant tumors,and specific mild heterogeneous enhancement. Key words: Melanoma; Nasopharyngeal neoplasms; Nasal cavity; Magnetic resonance imaging