Squamous and Basal Cell Carcinoma Surgical Margins

Updated on March 26, 2022

Medically reviewed by William Truswell, MD

Simple surgical excision (removal) is the most common method used to treat both primary and recurrent skin cancer tumors. The procedure involves surgically removing the tumor and a certain amount of normal-appearing skin surrounding it. This surrounding region is called the "margin" or "surgical margin."

Removing the margin maximizes the chance that all the cancerous cells will be removed. After the lesion is excised, it is sent to a pathologist who checks the margins of the excision to make sure they are clear.

Margins for Basal Cell and Squamous Cell Carcinomas

Primary and recurrent tumors get treated with marginal excisions. For example, one study showed that for low-risk basal cell carcinoma (BCC), margins are usually 3 to 4 mm, and high-risk margins are 5 to 10 millimeters based on the European Dermatology Forum with medical associations showing the same approximate margins. The study also showed low-risk squamous cell carcinoma (SCC), margins are usually 4 to 6 mm based on the National Comprehensive Cancer Network.

Excision may be performed in the outpatient or inpatient setting depending on the extent of cancer, though some more aggressive forms of tumors, recurrent tumors, or tumors on or adjacent to functionally significant structures, such as eyelids, lips, etc., may require a more involved procedure called Mohs micrographic surgery (MMS).

BCC and SCC are referred to as nonmelanoma skin cancers and are the most common forms of skin cancer, with BCC being more common than SCC; as many as 75% of nonmelanoma skin cancers are BCC.Despite being the most common skin cancers, nonmelanoma skin cancers only account for 0.1% of cancer deaths.

Margins for Melanoma Lesions

For melanoma lesions, the size of the margin is much larger and depends on the stage of the disease:

Stage 0: For melanoma in situ (in which cancer cells affect the top layer of skin [epidermis] only) standard margins may be 0.5 cm. For lentigo maligna, a subtype of in situ that occurs on sun-damaged skin, the margins are very irregular and may range from 6 mm (86% clearance rate) to 9 mm (98.9% clearance rate). MMS is generally recommended for this situation and for larger lesions.
Stage I: 1 to 2 cm, depending on the thickness of the melanoma (called the Breslow thickness).
Stage II: If the melanoma is 1 to 2 mm thick, a 1 to 2 cm margin of normal skin will be removed as well.
Stage III: A wide excision of the primary tumor depending on the thickness is followed by chemotherapy, immunotherapy, or other adjuvant treatments.

Basal Cell Carcinomas

Basal cell carcinomas, or BCCs, are abnormal growths or lesions in the skin's basal cells, which appear in the deepest layer of the outer layer of skin. BCCs commonly have a pink, pearly appearance often with a central ulcer (rodent ulcer). They may also appear as scars. BCC can be disfiguring, but rarely metastasizes beyond the tumor, though it can occur. Suspected BCCs should be examined and treated, and should not be ignored.

Basal cell carcinoma affecting the ear — Basal cell carcinoma on ear. DermNet / CC BY-NC-ND

Squamous Cell Carcinomas

Squamous Cell Carcinomas, or SCCs, are abnormal growths in the skin cells of the uppermost layers of the skin. SCCs commonly appear as open sores, scaly red patches, warts or growths that have a depression in the center. These may bleed or develops scabs, and they can be disfiguring. Though they are among the most common skin cancers and account for a relatively low percentage of deaths from cancer, they can metastasize and should not be ignored.

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