Because MCC is so rare, it is not usually suspected at the time of initial presentation. These tumors often present as firm blue or red, non-tender nodules. However, they may also present as plaques or lesions under the skin without changes in the overlying skin. The most common locations for these tumors are in the head and neck area and the extremities.
When a person with a concerning skin lesion is seen by a doctor, the doctor will perform a history and physical examination. The doctor will ask questions related to the risk factors for skin cancer and will focus on specific changes in the lesion that is of concern. The physical examination will include a full body skin exam, as well as examination of any swellings in the neck, the underarm area, and the groin, which may indicate spread of the disease.
In order to make a diagnosis of skin cancer, a piece of tissue from the skin lesion must be taken and evaluated. This is done by performing what is called a biopsy. There are generally two ways in which a biopsy is performed for MCC:
Punch biopsy: A punch biopsy is performed using a circular cutting device that takes out a cylinder of skin tissue. The biopsy device cuts through all layers of the skin using a circular motion down to the fat layer which is called the subcutaneous (below the skin) tissue. When performing a punch biopsy, a small amount of numbing medicine is injected into and around the lesion and then the core of tissue encompassing the lesion is removed. The skin defect is usually closed with 1 or 2 sutures. Punch biopsies are generally used in cases where the entire lesion may be removed by the punch biopsy device.
Excisional or incisional biopsy: An excisional or incisional biopsy is performed by using a scalpel (knife) to remove a sample of tissue. An excisional biopsy is generally used when the lesion is bigger than the usual punch biopsy devices but not so large that it will leave a large skin defect. An incisional biopsy is generally used for larger lesions when only a portion of the tissue is going to be sampled. In both cases, the biopsy area is injected with numbing medicine and then a piece of skin tissue is removed. As with the punch biopsy, the tissue sample will include all layers of the skin down to the fat layer. The biopsy site is then closed with several sutures.
Once a piece of the skin tissue is obtained, it is sent to a doctor who is specialized in looking at body tissues and can determine whether a skin cancer is present.