Final answer:
A malignant tumor from epithelial tissue is called a carcinoma. Carcinomas, which include basal cell and squamous cell carcinoma, can metastasize, unlike benign tumors. A biopsy is required for diagnosis, and melanoma, though also skin cancer, is distinct for being highly metastatic.
Step-by-step explanation:
A malignant tumor developing from epithelial tissue is known as a carcinoma. This type of cancer can originate in various parts of the body such as the breast, prostate, lung, and colon. Carcinomas include several types, such as basal cell carcinoma, which is the most common type of skin cancer and rarely metastasizes, and squamous cell carcinoma, another common skin cancer that affects the squamous cells in the epidermis.
The term 'malignant' refers to the ability of these tumors to invade nearby tissues and spread to other parts of the body, a process known as metastasis. This contrasts with benign tumors, which do not spread and are not cancerous. To confirm a diagnosis of carcinoma, a biopsy is usually performed, wherein a pathologist examines a tissue sample under a microscope. They may also distinguish different subtypes of carcinoma, such as small-cell and non-small-cell carcinoma of the lung, based on the cancer cells' appearance and behavior.
Melanoma, another type of skin cancer, is particularly aggressive and characterized by the uncontrolled growth of melanocytes. It is known for its potential to be highly metastatic and is the most fatal of skin cancers. Unlike basal cell carcinoma, melanoma tends to spread rapidly to other organs if not detected and treated early.