Basal cell carcinoma (BCC) represents the most frequently diagnosed form of skin cancer, originating from specialized cells in the skin’s outermost layer. This type of cancer is known for its generally slow growth pattern.
Understanding Basal Cell Carcinoma
Basal cell carcinoma develops from basal cells, a type of keratinocyte found in the deepest part of the epidermis. These cells are responsible for producing new skin cells, continuously pushing older ones to the surface where they eventually shed. The uncontrolled growth of these basal cells leads to the formation of a BCC.
The primary cause of BCC is often linked to prolonged or intense exposure to ultraviolet (UV) radiation, whether from sunlight or artificial sources like tanning beds. UV rays can damage the DNA within skin cells, leading to mutations that disrupt the normal cell growth cycle. While UV exposure is a major factor, about 20% of BCCs can arise on skin not typically exposed to the sun, suggesting other contributing elements.
Several factors can increase an individual’s risk of developing BCC. These include having fair skin that burns or freckles easily, a history of severe sunburns, and increasing age. Other risk factors involve a weakened immune system, previous radiation therapy, exposure to certain chemicals like arsenic, and genetic predispositions such as Gorlin syndrome.
How Basal Cell Carcinoma Appears and Grows
Basal cell carcinoma often begins as a small, seemingly benign spot on the skin. Over time, these lesions can manifest in various ways, with distinct clinical types presenting different visible characteristics as they progress.
Nodular BCC
Nodular BCC is the most common subtype, typically appearing as a pearly or waxy bump on the skin. These bumps often feature visible tiny blood vessels on their surface. As they grow, nodular BCCs may develop a central depression or ulceration and can be shiny or translucent. They commonly occur on sun-exposed areas like the face, particularly the nose, cheeks, and forehead.
Superficial BCC
Superficial BCC presents as a flat, reddish patch that can be scaly or crusty, often resembling inflammatory skin conditions. This type tends to spread outwards across the skin’s surface and is frequently found on the trunk, shoulders, or back. While it may initially be mistaken for a non-cancerous rash, its persistence and characteristic features distinguish it.
Morpheaform BCC
Morpheaform appears as a waxy, scar-like lesion that can be flat or slightly indented, often with ill-defined borders. This subtype is considered more aggressive due to its tendency to grow deeply beneath the skin’s surface, making its true extent difficult to determine visually. It commonly develops on the face and may be pale white or yellowish.
Pigmented BCC
Pigmented BCC is a less common variant that can appear dark. This coloration results from melanin within the tumor cells and can lead to misidentification as a mole or even melanoma. Despite its darker appearance, it shares underlying characteristics with other BCC types, such as being a shiny bump or an open sore that does not heal.
The Nature of BCC Progression and Local Spread
While basal cell carcinoma is generally slow-growing and has a very low propensity to metastasize, its local progression can be significant. This localized behavior means the primary concern with untreated BCC is its capacity for destructive growth within the surrounding tissues.
If left untreated, BCC can grow larger and invade deeply into adjacent structures. This local invasiveness can extend beyond the skin, potentially affecting underlying muscle, cartilage, and even bone. Such deep penetration can lead to substantial disfigurement, particularly when the tumor is located on sensitive areas like the face, near the eyes, nose, or mouth.
The progression of BCC can also result in functional impairment, especially in areas where the tumor encroaches upon structures necessary for normal bodily functions. For example, a BCC near the eye can affect vision or eyelid movement, while one near the nose might impact breathing. Nerve damage, characterized by symptoms like numbness or tingling, can also occur if the tumor invades nearby nerves. This local destruction underscores the importance of addressing BCC promptly to prevent severe localized consequences.