Substantial fetal masses may be malignant or benign. Benign masses are commonly seen as substantial masses or cystic masses with clear borders. Malignant masses are commonly found in substantial masses or mixed masses with unclear borders, uniform infiltrative growth, no complete envelope, rich blood supply in the mass, and relatively fast growth rate, so substantial masses are not necessarily malignant tumors. If it is benign, it can be removed by surgery and usually does not require other treatment. If it is malignant, it needs not only surgical resection but also radiotherapy or chemotherapy to avoid infiltration and metastasis. In addition, once a substantial mass is detected, patients should seek prompt medical attention to clarify the nature of the mass and its prognosis, and decide whether to continue the pregnancy.