原发性肛管直肠恶性黑色素瘤影像学诊断(5例报告及文献复习)

目的探讨原发性肛管直肠恶性黑色素瘤(AMM)的CT和MRI诊断价值。方法回顾性分析经组织病理学证实的AMM5例,其中男2例,女3例。4例行CT检查,1例行MRI检查。结果AMM表现明显蕈伞型肿块充满肠腔不伴肠梗阻(n=4),肠壁明显增厚(n=1);2例伴肠周脂肪浸润,其中1例延伸至骶前间隙;4例伴淋巴结转移,其中1例淋巴结直径>3cm。CT平扫示肿块呈稍低密度影,轻度强化1例、中度强化3例;AMM及其转移灶在MRIT1WI均呈高信号,T2WI为低信号。抑脂T1WI能更好地显示病灶范围及转移灶。结论肛门直肠部AMM可表现为腔内较大蕈伞型肿块,虽充满肠腔,但不伴肠梗阻,同时具较大淋巴结转移及明显肠周脂肪浸润。MRI对鉴别黑色素性AMM有提示价值。

Imaging Diagnosis of Anorectal Malignant Melanoma :A Report of 5 Cases with Literature Review

Objective To discuss the diagnostic value of CT and MRI for primary anorectal malignant melanoma(AMM).Methods 5 patients(2 males and 3 females)with AMM confirmed pathologically were analyzed retrospectively,which were examined by CT(n=4)and 1.5T MRI(n=1).Results AMM presented as bulky intraluminal fungating masses without intestinal obstruction(n=4)and irregular rectal wall thickening(n=1).2 cases had perirectal fat infiltration and extended to the presacral space in one case,4 cases had perirectal enlarged lymph nodes and larger than 3 cm in diameter in one case.Nonenhanced CT showed a hypodense lesion and contrast-enhanced CT showed slight enhancement(n=1)and mild enhancement(n=3).The tumor scanned by MRI depicted high intensity on T1WI and low intensity on T2WI,so did the enlarged lymph nodes and bone metastasis.Fat-saturation T1WI significantly improved the extention of tumor and detection of metastasis.Conclusion Bulky intraluminal fungating masses without intestinal obstruction,perirectal fat infiltration and enlarged lymph nodes may be helpful to diagnose AMM.MRI is especially useful in differentiating melanotic AMM from other rectal tumors.