Central nervous system tumors

Many kinds of TM can be detected in patients with intracranial GCT, but there are four kinds that are commonly used clinically: ① The main serum protein of AFP human fetus, which is 1 ~ 10ng/ml in normal children and has a molecular weight of 65 kildalton (kDa); ②β-HCG is secreted by normal placental syncytiotrophoblastic cells with a molecular weight of 45kDa; ③PLAP cell surface glycoprotein with molecular weight of 68kDa can be normally expressed in placental syncytiotrophoblast cells (STGC). CEA is a kind of glycoprotein with a molecular weight of 318kDa. The pathological subtypes of GCT were different, and the types and levels of TM expression were different.

1. Germ cell tumor

CT plain scan showed round irregular shape or butterfly shape, uniform or slightly high density, with or without calcification and cystic change; Reinforcement can show small cystic changes, mostly moderate to obvious uniform reinforcement, a few uneven reinforcement. Nodular calcification was observed around the lesion. The simultaneous discovery of tumor foci in the pineal region and sella region is conducive to the diagnosis of germinoma.

Most MRI scans showed equal or slightly longer T1 signal and slightly longer T2 signal, and occasionally T1 mixed with high-signal bleeding foci. Homogeneous reinforcement, clear boundary, only a few moderate or uneven reinforcement. The basal ganglia GE has its unique imaging features: the tumor volume is large, but the occupying effect is not obvious, the paratumoral edema is light, and the cerebral cortex atrophy in the ipsilateral fissure is common. The enhanced scanning showed irregular garland enhancement or speckled enhancement. Nagata believes that the mechanism of lateral fica atrophy is Wsllerian degeneration: tumor invasion and destruction of the brain's white matter, especially the nerve fibers of the inner sac.

It has been reported that 75-100% of GE patients are PLAP positive as measured by immunohistochemistry. If β-HCG<50IU/L, AFP>20ng/ml, PLAP positive, should be considered as pure germ cell tumor.

2. Teratoma and malignant teratoma

CT scan showed nodular, lobulated or irregular shape. The density is uneven, usually manifested as solid, cystic, calcification, ossification coexist, especially polycystic. The strengthening was characterized by significant but uneven strengthening of the solid part and polycyclic strengthening of the cyst wall. Although it is difficult to distinguish between benign and malignant teratoma on CT, generally speaking, the latter has a large solid part, relatively little cystic part, calcification and fat content, and common peritumoral edema.

Both MRT1 and T2 showed very mixed signals, both the entity and the cyst wall were significantly strengthened, the boundary was clear, and the morphology was mostly nodular and lobulated. If there is a flow of oil signals in the brain, the disease can be confirmed. Peritumoral edema suggests malignant teratoma.

TMCEA may be mildly or moderately elevated. AFP was significantly elevated in patients with immature teratoma and mixed GCT containing this component.

3. Endodermal sinus tumor

CT plain scan showed irregular solid tumor with low density, high density or mixed density, no cystic change, accompanied by different degrees of peritumoral edema, and some cases may have teratoma components.

MRI tumors showed equal or low signal on T1WI and uneven high signal on T2WI, with significant uneven enhancement after injection.

TM has a very important significance in the diagnosis and treatment of this type of tumor, and sometimes it is even more reliable than pathology, because the pathology is not complete and easy to miss the diagnosis. Patients with endodermal sinus tumor or mixed germ cell tumor containing endodermal sinus tumor components have positive AFP, if the serum AFP>1000ng/ml, the diagnosis can be confirmed. CEA may be mildly or moderately elevated.

4. Embryonic cancer

Plain CT scan showed a high density of tumors and sometimes calcification.

MRIT1WI is equal signal, T2WI is equal or high signal, obviously enhanced after injection, some cases have cystic change.

Serum β-HCG was increased in TM50% patients with embryonic carcinoma. CEA may be mildly or moderately elevated. AFP may be mildly or moderately elevated in patients with embryonic carcinoma and mixed intracranial germ cell tumors containing this component.

5. Chorionic epithelial carcinoma

Different from other intracranial germ cell tumors, chorionic epithelial carcinoma has its own imaging features and TM expression:

Plain CT scan is a slightly high-density image, which may have calcification and bleeding at the same time.

MRI plain scan T1WI or slightly higher or mixed signals, due to different periods of intratumoral subacute bleeding, tumor enhancement is obvious.

TM100% of chorionic epithelial carcinoma patients with elevated serum β-HCG, β-HCG increase can indicate that the tumor is choriocarcinoma or mixed germ cell tumor containing choriocarcinoma components, such as β-HCG>1000mlU/ml almost certainly choriocarcinoma or mixed germ cell tumor containing choriocarcinoma components. CEA may be mildly or moderately elevated.

Cerebrospinal fluid cytological examination, except for benign teratoma, intracranial germ cell tumors are prone to cerebrospinal fluid implantation and dissemination. Some patients can find shed tumor cells in cerebrospinal fluid, which is of great diagnostic significance, but the clinical detection rate is not high.

diagnosis.

Intracranial germ cell tumors mainly occur in suprasellar region, basal ganglia region, pineal region and other midline regions. Different pathological subtypes of tumors have their own characteristics in age, sex ratio, location distribution, disease course, clinical manifestations and imaging features. Based on this, a preliminary diagnosis can be made, but it is not sufficient to distinguish GCT from other tumors or GE from NGGCTs, and the final diagnosis depends on tumor marker (TM) level testing, cerebrospinal fluid cytology, and/or biopsy.