MRI征象在腮腺肿瘤定性诊断中的价值及其病理基础

Value of Manifestations of Magnetic Resonance Imaging(MRI) in Diagnosis of Parotid Tumors and Their Pathological Bases

背景与目的:腮腺肿瘤的病理类型非常复杂,MRI在其诊断中具有明显的优越性,但在诸多方面诊断标准仍不统一,需要大样本的病例分析以探讨MRI征象在其诊断中的价值及其病理基础。本文总结常见腮腺良、恶性肿瘤的MRI表现,以探讨各征象在腮腺肿瘤定性诊断中的作用。方法:收集132例腮腺肿瘤及其它病变患者(共140个病灶)的MRI资料,其中良性者89例,恶性者43例。112例经手术病理证实,17例经活检证实,3例经临床观察证实。对其中58例手术切除病灶完整者的标本行病理逐层切片检查,并将结果与MRI影像进行对照分析。MRI平扫采用T1WI、T2WI,其中108例共115个病灶同时行平扫和增强扫描。统计学分析采用χ2检验。结果:(1)常见腮腺良性肿瘤的MRI特征表现:所有行增强扫描的40个腺淋巴瘤均呈轻度增强,其中25例T2WI表现为低、等信号;22例混合瘤T2WI表现为高而不均匀信号;5例血管瘤可见异常增粗的血管结构;3例囊性淋巴管瘤的形状特别不规则并包绕邻近结构;4例脂肪瘤的信号类似于其它部位的脂肪瘤。(2)常见腮腺恶性肿瘤的MRI特征表现:8例混合瘤恶变的T2WI信号高而不均匀,且形状不规则,边界不清楚;7例腺样囊性癌以侵犯范围广泛为特征;8例粘液表皮样癌中,3例低度恶性者边界清楚,与良性肿瘤难区别,5例中、高度恶性者边界不清。

BACKGROUND &OBJECTIVE: The pathologic types of parotid tumor are very complicated and the advantage of magnetic resonance imaging (MRI) in diagnosis of these tumors is very obvious; however, there is not still accordance at several areas of MRI diagnosis of them. A large amount of cases are needed for analyzing these MRI features and their pathological fundament. This study was conducted to summarize the MRI manifestations of common benign and malignant tumors and to explore the value of the morphological features of MRI in histological diagnosis of parotid tumor. METHODS: The MRI manifestations for 132 cases(140 lesions) of parotid tumor/lesion were collected, including 89 benign tumors/lesions and 43 malignant tumors. Of them, 112 cases were proved by surgery, 17 cases by biopsy, and 3 cases by clinic observation. MRI features were completely compared with pathological results of surgical samples slice by slice in 58 cases. T1WI and T2WI sequence were used in MRI unenhancement scan; 108 cases (115 lesions) were examined with both unenhancement and enhancement. Chi square test was used for statistic analysis. RESULTS: (1) The MRI features of common parotid benign tumors were as following: 40 cases of Warthins tumors enhanced slightly and more than half of them (25 cases) appeared low or equal signal intensity in T2WI; 22 cases of pleomorphic adenoma appeared high and unhomogeneous signal intensity in T2WI; 5 cases of hemangioma were characterized by their vascular structures which were enlarged than normal; 3 cases of lymphangioma not only appeared specially irregular shape but also surrounded adjacent structures of parotid gland (3 cases). The features of 4 cases of parotid lipoma were same as those in other position of the body.(2) The MRI features of common parotid malignant tumors were as following: 8 cases of malignant pleomorphic adenoma appeared high and unhomogeneous signals in T2WI together with irregular shape and ill defined margin; 7 cases of adenoid cystic carcinoma characterized by invasion of very large range surrounding parotid gland. In 8 cases of malignant mucoepidermoid carcinoma,3 cases showed low grade malignant mucoepidermoid carcinomas, which had well defined margin and were difficult to distinguish from benign tumor. However, 5 cases of high grade malignant mucoepidermoid carcinoma showed ill defined margin, their features were tend to undergo necrosis and invade lymph node; 9 cases of lymphomas were all secondary lesions and there were two characters in their imaging, one was the wide involved range, the other was they consisted of several nodes. The shapes of 3 cases acinic cell carcinoma could be either regular or irregular, the cystic areas could be found in them with high signal intensity both on T1WI and T2WI. CONCLUSION: There are certain characters for each of common benign and malignant parotid tumors in MRI and these may be helpful for histological diagnosis in most of them.