What is metastatic skin cancer? A: Metastatic skin cancer is a lesion of malignant tumor secondary to skin through blood or lymphatic tract metastasis, tissue interstitial spread or surgical implantation. What are the most common manifestations of metastatic skin cancer? A: The clinical manifestations of metastatic skin cancer are diverse, most of them are nodules, followed by papules, plaques and scar-like tissue. There are also some metastatic cancers with clinical manifestations similar to many benign skin diseases such as erythema annulare, cellulitis, sclerosing chancre and lymphedema. What are the most common sites for metastatic skin cancer? A: In men, the most common sites are head, neck, chest and abdomen, while in women, chest and abdomen are the most common sites. What are the most common sites of metastatic skin cancer? A: Primary sites: mostly lung cancer, breast cancer, followed by gastrointestinal tumors. In women: breast tumor (69%), colorectal tumor (9%), malignant melanoma (5%), ovarian cancer (4%); in men: lung cancer (24%), colorectal tumor (19%), melanoma (13%), oral squamous cell carcinoma (12%). What is the importance of early detection of metastatic skin cancer? A: The appearance of skin metastatic cancer also indicates the possibility of metastasis from other parts of the tumor, and further examination of other parts should be done. Although the incidence is low, the diagnosis of metastatic skin cancer is very important because metastatic skin cancer is sometimes the first symptom of visceral tumor, which can help doctors detect the primary tumor early and prolong the survival time of patients to a certain extent. Can the primary site of metastatic skin cancer be found? A: Among the metastatic tumors in the whole body, some of them cannot be clearly identified as the primary site even after detailed clinical, imaging and histological examinations, and this group of tumors accounts for 5%-15% of all malignant tumors. If we can make a clear diagnosis from pathology, especially it can help to identify the primary site of tumor, it is important for further treatment and prognosis judgment of such tumors. How to confirm the diagnosis of metastatic skin cancer? A: Diagnosis mainly relies on tissue biopsy pathology, while X-ray, CT, PET-CT and blood tumor marker test are also very important for early detection of malignant tumor. Why do we need to do immunohistochemistry for metastatic skin cancer? A: In the past, it was difficult to make a clear diagnosis of metastatic cancer only by the observation of HE sections. In recent years, with the development of immunohistochemistry technology, a large number of valuable antibodies have been practically applied in the clinic, which provides great help to clarify the nature and origin of metastatic tumors.