Introduction to 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) Cause 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 cell genes to mutate and differentiation to be abnormal, 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, 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 tissues, 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. Xia Hui, Department of Cardiothoracic Surgery, The First Affiliated Hospital of the General Hospital of the Chinese People's Liberation Army

The pathological classification of teratomas is as follows: ① Mature teratomas: benign teratomas, composed of differentiated mature tissues, are the most common benign ovarian tumors; 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 symptoms and manifestations clinically 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. A careful abdominal physical examination and rectal digital examination are essential for the examination of abdominal, pelvic, and occult sacrococcygeal teratomas. X-rays of the tumor site can reveal abnormal calcifications of bones, teeth, etc. in the tumor to confirm the teratoma, which is mostly mature teratoma. 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 its adjacent relationship with important blood vessels and spinal nerves.

(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.

(5) Prognosis: The prognosis of teratoma is closely related to factors such as age at initial diagnosis, tumor location, incidence of malignant transformation, and treatment outcomes.

Complete removal of the tumor and reduction of postoperative recurrence and malignant transformation are another major prognostic factor for teratoma. Even for malignant teratoma, complete surgical resection is still the basic guarantee for long-term survival.