3肺部转移瘤的影像诊断

• 三、瘤周出血
比较典型的CT表现是结 节周围出现磨玻璃样密 度或边缘模糊的晕(晕 轮征)。但晕征不具特 异性，还可见于其他疾 病，如侵袭性曲霉菌病、 念珠菌病、Wegener肉 芽肿、伴咯血的结核瘤、 细支气管肺泡癌和淋巴 瘤等。胸片上表现为边 缘不规则的多发结节。 血管肉瘤和绒癌的肺转 移最易发生出血，可能 因为新生血管壁脆弱而 易破裂。
• Chest CT scans show a
spiculated mass in the apex of the left lung with multiple small nodular lesions in both lungs. Some of the nodules appear as cavitary or ring-like lesions. Discussion Cavitation of metastatic nodules is not as common as with primary lung carcinoma. The frequency of it is 4%, in contrast to 9% of primary lung carcinomas. Among metastatic nodules associated with cavitation, 70% are metastatic squamous cell carcinoma. The head and neck in males and the genitalia in females are the most common primary organ sites. Cavitation is observed rarely in metastatic adenocarcinoma, particularly that from colon cancer. Metastatic sarcoma can also be accompanied by cavitation, and pneumothorax is a relatively frequent complication. Chemotherapy is known to induce cavitation in metastatic pulmonary nodules.
• 二钙化
肺结节发生钙化常提示为良性，最常见于肉芽肿性病变，其次是错构瘤。但 有些恶性肿瘤的肺内转移性结节也可发生钙化或骨化，可见于骨肉瘤、软骨 肉瘤、滑膜肉瘤、骨巨细胞瘤、结肠癌、卵巢癌、乳腺癌、甲状腺癌的肺转 移和经治疗的转移性绒癌。钙化机制包括：①骨形成(骨肉瘤或软骨肉瘤)。 ②营养不良性钙化(甲状腺乳头状癌、骨巨细胞瘤、滑膜肉瘤或经过治疗的转 移性肿瘤)。③黏液性钙化(胃肠道和乳腺黏液腺癌)。CT是发现钙化的准确方 法，但不能区分转移性结节与肉芽肿性病变或错构瘤内的钙化。
临床经常遇到非典型肺转移，就需与其他肺部非恶性疾病相鉴别。 其放射学表现包括：空洞、钙化、瘤周出血、气胸、含气间隙病变、肿 瘤栓塞、支气管内膜转移、单发转移、瘤内血管扩张、灭活性转移瘤 (sterilized metastases)、良性肿瘤肺转移。
• 一、空洞
空洞较少见，仅占4%，，较原发肺癌发生率(9％) 低，其中70%为鳞癌转移。但最近有研究表明， 在CT上腺癌和鳞癌发生空洞性转移的几率无显著 性差异。此外，转移性肉瘤也可发生空洞，同时 合并气胸。化疗也可导致空洞形成。空洞的发生 机制常难确定，一般认为是肿瘤坏死或向支气管 内侵犯形成活瓣所致。空洞以不规则厚壁多见， 肉瘤或腺癌的肺转移可为薄壁空洞。肉瘤转移可 伴有空洞，但常合并有气胸
肺转移瘤 （Metastatic tumors of the lung）
• 肺是转移瘤的好发脏器，大量尸检结果显示，有20％～54％胸外恶性
肿瘤的病人发生肺转移。肺转移的途径可以是血行播散、淋巴道转移 或邻近器官直接侵犯。以绒毛膜癌、乳腺癌多见，恶性软组织肿瘤、 肝癌、骨肉瘤和胰腺癌次之；还有甲状腺癌、肾癌、前列腺癌和肾胚 胎癌等。 • 肺转移瘤以血行转移最为常见，血行转移为肿瘤细胞经腔静脉回流到 右心而转移到肺。瘤栓到达肺小动脉及毛细血管后，可浸润并穿过血 管壁，在周围间质及肺泡内生长，形成肺转移瘤。淋巴道转移多由血 行转移至肺小动脉及毛细血管床，继而穿过血管壁侵入支气管血管周 围淋巴结，癌瘤在淋巴管内增殖，形成多发的小结节病灶。常发生于 支气管血管周围间质、小叶间隔及胸膜下间质，并通过淋巴管在肺内 播散。肿瘤向肺内直接转移的原发病变为胸膜、胸壁及纵隔的恶性肿 瘤。 • 肺部转移性肿瘤较小时，很少出现症状，特别是血行性转移，咳嗽和 痰中带血并不多见。大量的肺转移可出现气促，尤其是淋巴性转移。 通常起病潜隐而进展较快，在数周内迅速加重。胸膜转移时，有胸闷 或胸痛。肺部转移性肿瘤变化快，短期内可见肿瘤增大、增多，有的 在原发肿瘤切除后或放疗、化疗后。有时可缩小或消失。
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粟粒样肺转移:
DMLD (diffuse micronodular lung disease), each nodule being < 3mm in diameter and occupying more than two-thirds of lung volume on chest radiograph, can be differentiated by its distribution. Centrilobular distribution is seen in DPB (diffuse panbronchiolitis), infectious bronchiolitis, H. influenza, bronchogenic disseminated tuberculosis, pneumoconiosis, primary lymphoma, and foreign body-induced necrotizing vasculitis. Perilymphatic distribution is noted in pneumoconiosis, sarcoidosis, amyloidosis. Random distribution is found in miliary tuberculosis and pulmonary metastasis. The nodules in pulmonary metastatic disease appeared to be slightly larger and are more variable in size than those in miliary tuberculosis. They show relatively well defined margins. Miliary metastases are most likely to be due to thyroid, renal carcinoma, bone sarcoma, trophoblastic disease, or melanoma.
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2. 淋巴道转移：淋巴转移以癌性淋巴管炎及淋巴结肿大为特征。多见于胃癌和乳腺癌。HRCT是诊断淋巴道转移的重要方法，当胸 片正常时，HRCT间有典型表现。表现为支气管血管束增粗，并有结节，小叶间隔呈串珠状改变或增粗，小叶中心有结节灶，并有 胸膜下结节。可并有肺门淋巴结增大，以单侧为主
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3. 肿瘤直接侵犯：纵隔、胸膜和胸壁的恶性肿瘤直接蔓延到肺部，表现为大小不等的转移灶。CT 和MRI可以显示肺内转移灶与原发灶的关系和肋骨及胸膜的侵犯情况。
• Hemorrahgic Metastasis from Choriocarcinoma （绒毛膜癌）Radiologic Findings
Chest radiograph shows multiple, ill-defined nodular opacities in both lungs. HRCT scan shows multiple, ill-defined nodules with halo of ground glass attenuation in the periphery zones of both lungs. Diagnosis was made based on clinical history of choriocarcinoma and radiologic findings. Serum HCG level was as high as 59,100 IU/ml.
Brief Review
The incidence of pulmonary metastases varies with the primary tumor and the stage of the disease. In autopsy series the most common sources of metastases to the lungs include tumors of breast, colon, kidney, uterus, prostate, head, and neck. Tumors such as choriocarcinoma, osteosarcoma, Ewing’s sarcoma, testicular tumors, melanoma and thyroid carcinoma have a high incidence of pulmonary metastases, but because they are not as prevalent in the population, lung deposits from these tumors are encountered less frequently . Hematogenous metastases usually result in multiple, large, well-defined nodules and tend to involve mainly the lower lung zones and frequently have a peripheral distribution. On occasion, if the metastases have bled into the surrounding lung, they show ill-defined edges. The reported incidence of pulmonary metastasis of choriocarcinoma has ranged from 5.1- 67% . The pattern of thoracic metastasis from choriocarcinoma is variable, including pulmonary nodules with surrounding hemorrhage, miliary nodules, nodule or masses with arteriovenous aneurysm formation, and pulmonary or pleural metastasis with spontaneous hemothorax .