Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are the two most frequently encountered types of non-melanoma skin cancer. These develop from different skin cells and exhibit distinct characteristics. This article clarifies the differences between BCC and SCC, covering their origins, appearances, behaviors, and management.
Understanding Basal Cell Carcinoma
Basal cell carcinoma originates from the basal cells in the deepest layer of the epidermis. This type of cancer commonly appears on sun-exposed areas such as the head, face, and neck, though it can occur anywhere on the body. It grows slowly and remains localized, rarely spreading to distant parts of the body.
BCC often presents as a pearly or waxy bump with a central depression and visible blood vessels. Other forms include a flat, flesh-colored or brownish scar-like lesion, or a reddish area that may bleed or itch. While not life-threatening, untreated BCC can cause significant local tissue destruction.
Understanding Squamous Cell Carcinoma
Squamous cell carcinoma develops from squamous cells in the upper layers of the epidermis. Like BCC, SCC frequently appears on sun-exposed skin, including the head, face, neck, and hands. However, it can also emerge in areas not typically exposed to the sun, such as scars, chronic wounds, or mucous membranes.
SCC lesions often present as a firm, red nodule or a flat lesion with a scaly, crusted surface. These may also ulcerate, bleed, or not heal properly. While SCC tends to remain localized, it carries a higher potential for aggressive growth and a greater risk of spreading to lymph nodes or other organs compared to BCC.
Key Distinctions Between BCC and SCC
A primary difference between BCC and SCC is their cellular origin: BCC arises from basal cells in the lower epidermis, while SCC develops from squamous cells in the upper epidermis. This fundamental distinction influences their growth patterns and potential behaviors.
Visually, BCC often presents as a shiny, pearly, or waxy bump with rolled borders and fine blood vessels, sometimes resembling a scar. In contrast, SCC typically appears as a firm, reddish nodule or a scaly, crusted patch that may bleed or form an open sore. While both occur on sun-exposed areas, SCC can also develop on non-sun-exposed sites and in areas with chronic inflammation.
Regarding growth patterns, BCC is known for its slow, localized growth, often expanding superficially or invading surrounding tissues gradually. It rarely spreads to distant sites, with metastatic rates estimated to be very low. SCC, however, can exhibit more rapid growth and has a higher, though still uncommon, propensity to spread to regional lymph nodes or, in rare cases, to distant organs.
Risk factors for both cancers primarily involve cumulative ultraviolet (UV) radiation exposure. SCC is additionally associated with chronic inflammation, radiation exposure, and human papillomavirus (HPV) infection. A history of BCC can increase the risk of developing future skin cancers, including SCC, but one type does not transform into the other.
Diagnosis and Treatment Approaches
The diagnosis of both BCC and SCC typically involves a skin biopsy. A small tissue sample from the suspicious lesion is removed and examined under a microscope to confirm the presence of cancer cells and determine the specific type. Common biopsy methods include shave, punch, or excisional techniques, depending on the lesion’s characteristics.
Once diagnosed, treatment approaches for BCC and SCC share commonalities, aiming to eliminate the tumor while preserving healthy tissue. Surgical removal is a frequent first-line treatment, often involving simple surgical excision of the cancerous lesion and a margin of healthy skin. Mohs micrographic surgery, a specialized technique, is effective for certain tumors, especially on the face or with ill-defined borders, allowing precise layer-by-layer removal while sparing healthy skin.
Other treatment options include curettage and electrodesiccation, which involves scraping away the cancer and then burning the base with an electric needle, often used for smaller, low-risk lesions. Radiation therapy, using high-energy rays to destroy cancer cells, may be considered for tumors in surgically challenging areas or for patients not candidates for surgery. Topical medications, such as imiquimod or fluorouracil creams, can be used for superficial forms of these cancers.
Prognosis and Management
The prognosis for both BCC and SCC is generally favorable, particularly when detected and treated early. Both are highly curable, with successful treatment rates for early-stage lesions often exceeding 90%. SCC carries a slightly higher risk of recurrence and more serious outcomes if untreated or if it develops high-risk features.
Individuals with a history of BCC or SCC have an increased risk of developing new skin cancers. There is a 35% chance of developing another non-melanoma skin cancer within three years and a 50% chance within five years.
Ongoing management includes regular self-skin exams to monitor for new or changing lesions. Annual professional skin checks by a dermatologist are also recommended for continued surveillance. Consistent sun protection practices, including broad-spectrum sunscreen, protective clothing, and seeking shade, are strongly advised to minimize the risk of developing new lesions and prevent recurrence.