There are many types of skin diseases, and amidst them there are a lot of tumours. Some of them are harmless and need no treatment. These are called benign tumours. Some are cancerous and must be removed early. These are called malignant tumours.
Now, what are some of the benign skin tumours?
Seborrhoeic keratosis are brown to black growths on the face and body. They are usually present on the skin of people over 40 years old. The tumours appear as if they are "stuck-on" the skin. Sometimes, they can be very dark. The surface is usually rough and can be greasy. There may be multiple, distributed on the face, body and limbs. They can be left alone but may be removed by minor surgery for cosmetic reasons.
Skin Tags are skin coloured lumps that grow out of the skin. They are soft and usually found on the neck, armpits and body. These are harmless but can be removed by minor surgery for cosmetic reasons.
Sebaceous hyperplasia are enlarged oil glands on the face which appear as small yellow irregular lumps with an opening in the centre. They are often seen on the face of elderly persons. They can be removed by minor surgery.
Syringomas are benign growths of the sweat ducts. They appear as small skin-coloured lumps usually on the eyelids and cheeks. They are painless. They can be removed by minor surgery for cosmetic reasons.
Xanthelasma  are raised yellow-coloured patches appearing on the eyelids. They represent oily deposits in the skin. These lesions may be associated with high fat content in the blood. Therefore, anyone with these lesions should see a doctor to see if they have any underlying medical problem that needs treatment. The lesions can be removed by minor surgery.
Then, how are benign growths treated ? Most these skin diseases can be destroyed by electro-surgery or laser surgery. Electro-surgery is a procedure whereby the tumours are destroyed using a needle attached to an electric current. When the current is switched on, the electrical energy is converted to heat energy which will burn off the tissue. Laser surgery removes skin tumours by high energy light. These procedures are painless under local anaesthesia.

As to the malignant tumours, most skin cancer can be effectively treated if detected early. You should visit your doctor at least once a year, and conduct a self-exam
about every 3 months. The signs of skin cancer to look for are  moles, brown spots or pearly bumps that have changed in color, size or shape; a new growth of skin that may increase in size; a change in skin texture including scaly red patches or crusty areas that may itch, bleed or scab; a sore that does not heal.

The skin is the largest organ of the body and certainly the most visible. Although many skin diseases are isolated, a significant portion of skin symptoms reflects a more generalized disease that affects other organs. Hence, a dermatologist is required to have a working knowledge of basic surgery, rheumatology (many rheumatic diseases can feature skin diseases symptoms), neurology, and endocrinology. Dermatology is often practiced in tandem with venereology, the specialism that diagnoses and treats sexually transmitted diseases, and phlebology, the specialism that deals with problems of the superficial venous system. The recent trend is to club dermatology with cosmetology. This incorporates the use of  lasers and other light sources to enhance one's looks.