病理診斷：毛黏液樣星形細(xì)胞瘤

毛黏液樣星形細(xì)胞瘤( pilomyxiod astrocytoma,PMA),先前被認(rèn)為就是PA,或者是一種臨床不典型的PA。1999年由Tihan等首次對(duì)其進(jìn)行命名并指出PMA是毛細(xì)胞型星形細(xì)胞瘤的一種亞型,2007年WHO中樞神經(jīng)系統(tǒng)腫瘤分類新增補(bǔ)為毛細(xì)胞型星形細(xì)胞瘤的一種亞型,歸入神經(jīng)上皮性腫瘤,屬WHOⅡ級(jí)。與PA相比,PMA呈現(xiàn)更為復(fù)雜的生物學(xué)行為,具有較強(qiáng)的侵襲性,局部復(fù)發(fā)和腦脊液播散更常見。

Pilomyxiod astrocytoma (PMA) was previously known as PA, or clinically atypical PA. In 1999 by Tihan etc. For the first time on the naming and points out that the PMA is a form of type pilocytic astrocytoma , in 2007 the WHO classification of the central nervous system tumors new additions as a form of type hair cell astrocytoma, into neuroepithelial tumors, belong to the WHO Ⅱ level. Compared with PA,PMA presents more complex biological behaviors, is more aggressive, and local recurrence and CSF dissemination are more common.

PMA又稱為PA亞型或PA嬰兒型,多見于兒童和幼兒,平均發(fā)病年齡為18個(gè)月,也可見于青少年,成人罕見。PMA好發(fā)于中線區(qū)域,多在視交叉、下丘腦、鞍區(qū)、丘腦,也可見于其他位置包括小腦半球、大腦半球和脊髓。腫瘤的發(fā)生位置和發(fā)病年齡有一定的相關(guān)性,發(fā)生于不典型位置者多見于年齡較大者。PMA對(duì)周圍的血管神經(jīng)更具侵襲性,手術(shù)通常難以完全摘除,臨床治療般以部分切除輔以術(shù)后化療為主。不論全切或部分切除,大部分腫瘤常在1年內(nèi)復(fù)發(fā),局部復(fù)發(fā)率約為76%。

PMA, also known as PA subtype or PA infantile type, is more commonly seen in children and young children, with an average age of 18 months. It can also be seen in adolescents, but is rare in adults. PMA tends to occur in the midline region, mostly in the optic chiasma, hypothalamus, sellar region and thalamus, but also in other locations including cerebellar hemisphere, cerebral hemisphere and spinal cord. There is a correlation between the location of tumor and the age of tumor onset. PMA is more invasive to peripheral blood vessels and nerves, and it is usually difficult to completely remove the peripheral blood vessels and nerves. The majority of tumors recurred within 1 year, regardless of total or partial resection, with a local recurrence rate of about 76%.

大體所見毛細(xì)胞黏液樣星形細(xì)胞瘤在術(shù)中病理報(bào)道中常被描述為質(zhì)地較硬的膠樣腫塊,腫瘤可浸潤周圍腦實(shí)質(zhì)。顯微鏡下顯示其組織學(xué)特點(diǎn)為顯著黏液樣變的基質(zhì)和單一形態(tài)的雙極細(xì)胞,以血管為中心分布,腫瘤組織內(nèi)部可見微血管增殖,但是無Rosenthal纖維或嗜酸性顆粒小體/玻璃樣小滴

The gross appearance of a  pilomyxiod astrocytoma is often described as a hard, gelatinous mass that can infiltrate the surrounding brain parenchyma. Microscopically, the histological features of the stroma are marked by mucoid-like changes and single morphologic bipolar cells, centered around blood vessels, with microvascular proliferation visible within the tumor tissue, but without Rosenthal fibers or eosinophilic granulocytes/hyaline droplets

CT表現(xiàn)為邊界清楚的腫塊,實(shí)性居多,囊變少見,其影像特征與低級(jí)別膠質(zhì)瘤相似。實(shí)性部分及囊壁呈等或稍低密度,囊性部分呈明顯低密度,瘤內(nèi)有出血時(shí)呈高密度。增強(qiáng)后腫瘤實(shí)性部分及囊壁呈不均勻強(qiáng)化,可有占位效應(yīng),?？蓪?dǎo)致腦積水

CT findings showed a well-defined mass, mostly solid, with few cystic changes. The imaging features were similar to those of low-grade gliomas. The solid part and the cystic wall showed equal or slightly lower density, the cystic part showed significantly lower density, and the hemorrhage in the tumor showed higher density. After enhancement, the solid part of the tumor and the capsule wall showed uneven enhancement, which could have space-occupying effect and often lead to hydrocephalus

MRI腫瘤表現(xiàn)為實(shí)性、囊實(shí)性,呈圓形或分葉狀。PMA的MR表現(xiàn)由于組成成分的不同而存在差異。腫瘤多邊界清晰,極少數(shù)與周圍腦組織分界不清,腫瘤周圍水腫少見。實(shí)性部分及囊壁在T1WI上呈稍低或等信號(hào),T2WI呈高或稍高信號(hào),并于高信號(hào)內(nèi)見條狀低信號(hào)。增強(qiáng)掃描實(shí)性成分呈明顯環(huán)狀強(qiáng)化,這可能與腫瘤細(xì)胞“血管中心樣生長”有關(guān);也可見部分實(shí)性成分無強(qiáng)化,與腫瘤內(nèi)可能存在壞死、囊變或腫瘤組織學(xué)含大量黏液基質(zhì)有關(guān)。腫瘤囊性部分在T1WI上呈明顯低信號(hào),T2WI上呈高信號(hào),少數(shù)呈低信號(hào)。當(dāng)PMA發(fā)生在大腦半球,MR影像有相對(duì)特征性表現(xiàn):多位于大腦半球較表淺位置。表現(xiàn)為囊性病灶伴附壁結(jié)節(jié),附壁結(jié)節(jié)在T1WI上呈等低信號(hào)、在T2WI上呈高信號(hào),增強(qiáng)掃描呈“星芒狀”強(qiáng)化,有時(shí)PMA可伴有腦膜和脊膜的強(qiáng)化,提示腫瘤細(xì)胞已侵犯或播散至腦膜和脊膜。PMA在T2-FLAIR像上實(shí)性部分大多呈高信號(hào),少數(shù)呈等信號(hào),囊性部分多呈低信號(hào),腫瘤邊緣亦可呈高信號(hào)。PMA因其發(fā)生部位、病灶大小的不同,占位效應(yīng)也各不相同。發(fā)生于視交叉和下丘腦區(qū)的PMA,隨著病灶體積的增大,可以侵及兩側(cè)頸內(nèi)動(dòng)脈、視神經(jīng)及大腦中動(dòng)脈,若病灶發(fā)生在腦實(shí)質(zhì)內(nèi),常會(huì)導(dǎo)致中線結(jié)構(gòu)移位。PMA可引起阻塞性腦積水,但瘤周水腫多不明顯。24%腫瘤內(nèi)有瘤內(nèi)出血。

MRI tumor was solid, cystic and round or lobulated. MR performance of PMA varies with different components. Many tumors have clear boundaries, few of them have unclear boundaries with the surrounding brain tissue, and edema around the tumor is rare. The solid part and capsule wall showed a slightly lower or equal signal on T1WI, while the T2WI showed a high or slightly higher signal, and a strip of low signal was observed in the high signal. The solid components of the enhanced scan showed obvious ring enhancement, which may be related to the 'vascularized growth' of tumor cells. It is also observed that some solid components are not strengthened, which may be related to necrosis, cystic degeneration or tumor histology containing a large amount of mucous matrix. The cystic part of the tumor showed obvious low signal on T1WI, high signal on T2WI, and a few showed low signal. When PMA occurs in the cerebral hemisphere,MR images have a relatively characteristic appearance: they are usually located in the superficial position of the cerebral hemisphere. It was manifested as cystic lesions with mural nodules, which showed equal low signal on T1WI and high signal on T2WI. Enhanced scanning showed stellar-like enhancement, and sometimes PMA was accompanied by enhancement of meninges and spinal membranes, suggesting that tumor cells had invaded or spread to meninges and spinal membranes. PMA in t2-flair images was mostly hypersignal in the solid part, few in the isosignal, mostly in the cystic part, and also hypersignal in the edge of the tumor. According to the location and lesion size of PMA, the space occupying effect is also different. PMA occurs in the optic chiasm and hypothalamus, and with the increase of lesion volume, it can invade bilateral internal carotid artery, optic nerve and middle cerebral artery. If the lesion occurs in the brain parenchyma, the midline structure will often be shifted. PMA can cause obstructive hydrocephalus, but the peritubercular edema is not obvious. 24% of the tumors had intratumoral hemorrhage.

DWI上腫瘤可表現(xiàn)為低信號(hào)或高信號(hào),但ADC圖為高信號(hào),腫瘤實(shí)性部分的ADC值增高,與腫瘤內(nèi)富含黏液,瘤體組織中水分子擴(kuò)散不受限有關(guān)。MRS上表現(xiàn)為Cho和Lip峰增高,而Cr和NAA峰降低,部分可見腫瘤周圍區(qū)域Cho、Cr比值升高,這可能與PMA具有浸潤和侵襲性相關(guān)。

On DWI, tumors may show low or high signal, but ADC picture shows high signal. ADC value of solid part of the tumor increases, which is related to the fact that the tumor is rich in mucus and the diffusion of water molecules in the tumor tissue is not restricted. Cho and Lip peaks were increased on MRS, while Cr and NAA peaks were decreased. Cho and Cr ratios were increased in some areas around the tumor, which may be related to invasion and invasion of PMA.

PMA診斷要點(diǎn)包括:多見于兒童和幼兒;好發(fā)于近中線的神經(jīng)軸部位,多在視交叉、下丘腦、鞍區(qū)、丘腦;CT平掃實(shí)性部分及囊壁呈等或稍低密度,囊性部分呈明顯低密度,瘤內(nèi)有出血時(shí)呈高密度;MR檢查T1WI上多為低信號(hào),T2WI多為高信號(hào),T2-FLAIR序列呈高信號(hào),增強(qiáng)掃描實(shí)性部分多數(shù)呈環(huán)狀明顯強(qiáng)化;DWI上呈低信號(hào);MRS上Cho和Iip峰增高,而Cr和NAA峰降低。

Diagnosis of PMA includes: it is more common in children and young children; It is more likely to occur in the nerve axis near the midline, mostly in the optic chiasma, hypothalamus, sella region and thalamus. CT scan showed equal or slightly lower density of the solid part and the cystic wall, significantly lower density of the cystic part, and higher density of bleeding in the tumor. MR examination showed low signal on T1WI, high signal on T2WI, high signal on t2-flair sequence, and obvious ring enhancement on the solid part of enhanced scanning. Low signal on DWI; Cho and Iip peaks on MRS increased, while Cr and NAA peaks decreased.

PMA主要與毛細(xì)胞型星形細(xì)胞瘤、血管網(wǎng)狀細(xì)胞瘤、室管膜瘤、生殖細(xì)胞瘤及侵襲性垂體瘤相鑒別。

1.毛細(xì)胞型星形細(xì)胞瘤兒童及青少年發(fā)病,幕下常見,囊性及附壁結(jié)節(jié)或囊實(shí)性為主,增強(qiáng)掃描壁結(jié)節(jié)及實(shí)性部分明顯強(qiáng)化,一般不伴瘤周水腫。

pilocytic astrocytoma  is common in children and adolescents. It is mainly cystic and mural nodules or cystic solid. Enhanced scanning of mural nodules and solid parts is obviously enhanced.

2.血管母細(xì)胞瘤常有家族史,是常染色體顯性遺傳性疾病,好發(fā)于30-65歲成年人,小腦為好發(fā)部位,多數(shù)呈大囊小結(jié)節(jié)樣改變,瘤壁結(jié)節(jié)明顯強(qiáng)化,內(nèi)壁光整,形成“壁燈征”,并可見流空的血管。  

Hemangioblastoma often has a family history, is an autosomal dominant disease, and is prone to occur in adults aged 30-65 years old. Cerebellum is the most common site of occurrence, and most of them show small nodular changes in large bursa. The nodules on the tumor wall are obviously strengthened, the inner wall is smooth, forming a 'wall lamp sign', and empty vessels can be seen.

3.PMA發(fā)生于第四腦室時(shí)需與第四腦室室管膜瘤相鑒別,后者主要發(fā)生在兒童和青少年,T1WI呈等或低信號(hào),T2WI呈高信號(hào),腫瘤多呈不規(guī)則形,邊緣不光整,可伴有鈣化,增強(qiáng)掃描呈不均強(qiáng)化,常伴瘤周水腫。  

When PMA occurs in the fourth ventricle, it is necessary to differentiate it from the fourth ventricle ependymoma, which mainly occurs in children and adolescents. T1WI shows equal or low signal, while T2WI shows high signal. The tumors are mostly irregular shape, with uneven edges, and may be accompanied by calcification.

4.生殖細(xì)胞瘤發(fā)生于鞍區(qū)時(shí)缺乏典型特征,可呈實(shí)性、囊實(shí)性,與鞍區(qū)PMA較難鑒別,但生殖細(xì)胞瘤多較小,對(duì)放療敏感,且常有下丘腦內(nèi)分泌異常癥狀。

Germ cell tumors occur in the saddle region without typical features, can be solid, cystic solid, and difficult to identify with PMA in the saddle region, but germ cell tumors are more small, sensitive to radiotherapy, and often have hypothalamic endocrine abnormalities 

5.侵襲性垂體瘤MRI上瘤體?？梢姵鲅獕乃馈⒛易?并常見海綿竇受侵、頸內(nèi)動(dòng)脈被包繞征象,腫瘤內(nèi)常有血管流空信號(hào)。

On MRI, the tumor of invasive pituitary tumor often has hemorrhage, necrosis and cystic changes, and the invasion of cavernous sinus and the wrapping of internal carotid artery are common, and the signal of vascular empylate is often found in the tumor.

PS:預(yù)后:毛細(xì)胞黏液樣星形細(xì)胞瘤與毛細(xì)胞星形細(xì)胞瘤相比較,毛細(xì)胞黏液樣星形細(xì)胞瘤更具侵襲性,且局部復(fù)發(fā)和腦脊液播散更為常見,因此預(yù)后不良。

pilomyxiod astrocytomas are more aggressive than pilocytic astrocytomas, and local recurrence and CSF dissemination are more common, so the prognosis is poor.