Causes of early teratoma

Teratoma is a tumor covered by a membrane. In the tumor, many tissues similar to normal organs can be seen mixed, such as hair, cartilage, glands, etc. These tissues may originate from three germ layers. Mediastinal teratoma is a germ cell tumor occurring in the mediastinum. There are different views on its histological origin. So what are the causes of early teratoma?

1. Causes of disease

Ovarian immature teratoma is composed of mature and immature embryonic tissues from the three germ layers, which may show that one germ layer is immature or incompletely differentiated, or (2-3 germ layers are immature). Mature and immature tissues are often mixed.

2. Pathogenesis

1. The tumor is usually a unilateral giant mass, and the contralateral ovary may be combined with a benign teratoma. The capsule is smooth, but often adheres to the surrounding tissues or is torn during surgery. The cut surface is mostly solid, with cystic areas; occasionally, the cystic area has solid areas on the cyst wall. The solid area is soft and delicate, with bleeding and necrosis, and is colorful, sometimes with bone, cartilage, hair or brain tissue; the cystic area is usually filled with serous, mucous or jelly-like substances.

2. Microscopically, it is composed of mature and immature tissues from three germ layers; the ectoderm is mainly nerve tissue and skin, the mesoderm is mainly fibrous connective tissue, cartilage, bone, muscle and undifferentiated mesenchymal tissue, and the endoderm is mainly glandular duct-like structure, and sometimes bronchial or gastrointestinal epithelium can be seen. These tissues are in different stages of maturity and have no organ-like arrangement. Immature tissue mainly refers to neuroepithelial tissue, which can form rosettes or neural tube structures, or diffuse into pieces.

Based on the content of this neuroepithelium in the tumor, some scholars have proposed a grading method for immature teratomas, which is of great significance for both treatment and prognosis.

Level 0: All are mature organizations.

Grade I: There is a small amount of immature tissue (mainly glial and primitive mesenchyme), nuclear division can be seen, and there is little neuroepithelium, limited to 1/40x field of view in each section.

Grade II: There is a lot of immature tissue, but the neuroepithelium does not exceed 3/40x field of view in each section.

Stage III: There is a large amount of immature tissue, with the amount of neuroepithelium occupying 4 or more/40 times the field of view in each section, and it is often fused with sarcomatous stroma.

This pathological grading method has been widely used. Some scholars have also proposed that the amount of neuroepithelium in each section is 10% as grade I, 10% to 33% as grade II, and more than 33% as grade III. In order to reduce the inconsistency of grading, Norris et al. recently proposed to merge this grading into two categories: low-grade malignancy and high-grade malignancy, that is, grade I that does not require chemotherapy and grades II and III that require postoperative chemotherapy. These grading methods must be based on sufficient sampling, and one piece of material should be taken for every centimeter of the maximum diameter of the tumor in areas with different macroscopic morphology. If the tumor is >20cm, at least 20 pieces of tissue should be taken for examination.

The morphology and tissue grade of metastatic lesions may be different from those of the primary tumor. Some of them form many nodules of varying sizes on the peritoneal surface, which are well-differentiated glial cells under the microscope. This is called peritoneal gliomatosis. This type of implanted nodules is benign and will disappear on its own after the primary tumor is removed.