原发性黑素细胞病变

Primary Melanocytic Lesions

原发性黑素细胞病变是一组起源于软脑膜黑素细胞的、呈弥漫性或局限性生长的良、恶性肿瘤 ,包括 :①弥漫性黑素细胞增生症 ;②黑素细胞瘤 ;③恶性黑素瘤 ;④脑膜黑素瘤病。可出现交界性或混合性肿瘤。弥漫性黑素细胞增生症的CT和MRI表现为软脑膜的弥漫性增厚、强化。黑素细胞瘤内如含有较多的黑素 ,则表现为T1WI高信号、T2WI低信号 ,增强时肿瘤通常出现均匀强化表现。恶性黑素瘤也可表现为T1WI高信号、T2WI低信号 ,主要取决瘤体内黑素含量和是否伴有出血 ,增强时肿瘤通常也出现均匀强化表现。脑膜黑素瘤病可以表现为脑内外多发的T1WI高信号、T2WI低信号结节影 ,增强后可出现脑膜的弥漫性强化和(或)脑内的结节状强化。

Primary melanocytic lesions are a group of diffuse or circumscribed,benign or malignant tumors arising from melanocytes of the leptomeninges.This group includes:①diffuse melanocytosis(diffuse melanosis),②melanocytoma,③malignant melanoma,and ④meningeal melanomatosis,but intermediate or mixed cases may occur.CT and MRI of diffuse melanocytosis show diffuse thickening enhancement of the leptomeninges.Melanocytoma appears hyperintense on T1WI and hypointense on T2WI images,if the tumor contains enough melanin pigment;on postcontrast images the tumor usually is enhanced homogeneously.Malignant melanoma also may appear hyperintense on T1WI and hypointense on T2WI images depending on the amount of melanin pigment and hemorrhage in the tumor,on postcontrast images the tumor usually is enhanced homogeneously.Meningeal melanocytosis may appear multiple T1WI hyperintense and T2WI hypointense nodular lesions inside and outside the brain with diffuse meningeal and/or nodular enhancement of the leptomeninges and lesions in the brain on postcontrast images.All these appearances are nonspecific for the primary melanocytic lesions.