Introduce some questions about teratoma

Teratomas originate from potentially multifunctional primitive embryonic cells and are mostly benign, but the tendency to be malignant increases with age. The site of occurrence is related to the midline anterior axis or midline paracentral area of ​​the embryological body cavity, and is often seen in the sacral and coccygeal region, mediastinum, retroperitoneum, and gonadal region. They are more common in newborns and infants, and are more common in women.

(1) Causes and pathology:

During the development of human embryos, there is a type of pluripotent cell with pluripotent development potential. Under normal embryonic development, it develops and differentiates into mature cells of each germ layer. If some pluripotent cells separate or fall off from the whole at different stages of the embryo, causing mutations in cell genes and abnormal differentiation, embryo abnormalities may occur. It is generally believed that if this separation or shedding occurs in the early embryo, a teratoma will be formed; if it occurs in the late embryo, an abnormally differentiated tissue with three germ layers of endoderm, mesoderm and ectoderm will be formed, that is, a teratoma will be formed.

The pathological characteristics of teratoma are that the tumor tissue is composed of three germ layers: the outer, middle and inner germ layers, and often contains mature or immature skin, teeth, bones, cartilage, nerves, muscles, fat, epithelium and other tissues. A few may also contain gastric mucosa, pancreas, liver, kidney, lung, thyroid and thymus tissue components. Malignant teratomas often appear as immature tissues that are difficult to define and distinguish. The malignant transformation of teratomas is often manifested as abnormal proliferation of neural tissue or epithelial tissue to form malignant teratomas.

The pathological classification of teratomas is as follows: ① Mature teratomas: benign teratomas, composed of differentiated and mature tissues; ② Immature teratomas: malignant teratomas, composed of immature tissue structures during the embryogenesis period, mostly glial or neural tube-like structures, often with undifferentiated, increased mitotic malignant pathological manifestations. In the past, germ cell malignancies such as seminoma, dysgerminoma, embryonal carcinoma, and endodermal sinus tumor were collectively referred to as malignant teratomas. In fact, they are embryological germ cell tumors, the result of abnormal differentiation in various areas of migration from the yolk sac to the gonads. Pathologically, they often do not have the three germ layer structure and should not be classified as teratomas.

(2) Clinical manifestations:

Teratomas may present with various clinical symptoms and manifestations due to their different locations, multiple complications, and obvious malignant tendencies:

① Painless mass: This is the most common symptom of teratoma. It is usually round and cystic with clear boundaries and uneven hardness. Even bony nodules can be palpated. Exophytic tumors are common in the midline of the sacrum, occipital, forehead, and nose. Sacrococcygeal teratoma can be divided into three clinical types according to its location: overt, latent, and mixed.

②Compression and cavity obstruction symptoms: Mediastinal teratomas can often compress the respiratory tract and cause choking, dyspnea, and distended neck veins; retroperitoneal teratomas often cause abdominal pain and can cause intestinal obstruction. Pelvic and sacrococcygeal occult teratomas are often diagnosed due to constipation, difficulty defecating, and urinary retention.

③ Acute symptoms of abnormal tumor changes: Ovarian and testicular teratomas may cause ovarian or testicular torsion and necrosis, manifested by severe pain and corresponding local symptoms; when secondary infection and intracystic bleeding occur in teratomas, the tumor may often increase rapidly, with obvious local tenderness, and accompanied by fever, anemia, shock and other systemic infection or blood loss symptoms; tumors in the retroperitoneum, ovaries, pelvis, sacrum and coccyx may also suddenly rupture and cause massive bleeding, hemoperitoneum, shock and other dangerous manifestations.

④ Symptoms of tumor malignancy: When malignant teratomas and benign teratomas become malignant, they often show rapid tumor growth and loss of original elasticity. For exophytic tumors, superficial veins may be dilated and congested, and local skin may be infiltrated with increased skin temperature. Lymph node enlargement and lung and bone metastasis may occur through lymphatic and blood circulation, and systemic symptoms such as weight loss, anemia, and tumor fever may also occur.

(3) Diagnosis:

Most teratomas are exophytic or have obvious palpable masses, and early diagnosis can often be achieved based on clinical manifestations. Careful abdominal physical examination and rectal digital examination are very necessary for the examination of abdominal, pelvic, and occult sacrococcygeal teratomas; X-ray films of the tumor site can reveal abnormal calcifications of bones, teeth, etc. in the tumor to confirm the teratoma, and most of them are mature teratomas; gastrointestinal barium meals, barium enema, and intravenous pyelography can understand the compression and displacement of the gastrointestinal tract or organs such as the kidneys, ureters, and bladder in the corresponding parts. CT and MRI examinations should be performed on teratomas that grow rapidly and have a wide range of infiltration to clarify the range of tumor infiltration and the adjacent relationship with important blood vessels and spinal nerves. For those who consider the possibility of malignant teratoma, the levels of alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) in the serum of children should be tested, which will guide the diagnosis and prognosis. 92% of malignant teratomas have elevated alpha-fetoprotein, while 4% of benign teratomas also have abnormal AFP. It was found that the postoperative recurrence rate was significantly increased in benign teratomas with elevated AFP.

(4) Treatment: Once a teratoma is diagnosed, early surgical resection is necessary to prevent benign teratoma from becoming malignant due to delayed surgery. It can also prevent tumor infection, rupture, bleeding and complications. The key point of teratoma surgery is to completely remove the tumor. For ovarian and testicular tumors, one ovary or testicle should be removed. For sacrococcygeal teratoma, it is important to remove the coccyx at the same time to avoid residual pluripotent cells that may cause tumor recurrence.

The treatment principle of malignant teratoma is combined adjuvant therapy. Conventional chemotherapy is used for 1.5 to 2 years after surgical resection. Cisplatin, vinblastine or vincristine, and bleomycin are commonly used. In recent years, combined chemotherapy with cisplatin, doxorubicin, ifosfamide and other chemotherapy drugs is recommended. Radiotherapy is only used for cases of malignant teratoma with clear microscopic or macroscopic residuals. The radiotherapy dose is preferably 25Gy for microscopic residuals, and 35Gy can be used for macroscopic residuals. For those with complete surgical resection, chemotherapy is advocated in recent years, and radiotherapy is used with caution to avoid delayed damage to reproductive organs and bone development during radiotherapy.

For patients with large or extensively infiltrated malignant teratomas that are clinically judged to be unresectable, preoperative chemotherapy or radiotherapy can be used to shrink the tumor before delayed radical surgery, which is of positive significance in improving the surgical resection rate and preserving important organs. For advanced cases, preoperative chemotherapy or radiotherapy can also achieve the therapeutic purpose of relieving tumor compression, controlling metastatic lesions, and gaining the opportunity for another surgery.