Basal Cell Cancer
Basal cell carcinoma (BCC) is the most common malignant cutaneous neoplasm in humans. The most common presenting complaint is a bleeding or scabbing sore that heals and recurs. The tumor rarely metastasizes. BCC advances by direct extension and destroys normal tissue. Untreated, the cancer can destroy the whole side of the face or penetrate subcutaneous tissue into the bone and brain.
Risk factors.
Fair skin and the degree of sun exposure are important risk factors. Outdoor workers and people who live in southern latitudes with higher levels of ambient ultraviolet B radiation are at greater risk. Men have a significantly higher incidence than women. Tanning salons with equipment that emits ultraviolet A or B radiation are also damaging and increase the risk of BCC.
Location.
Eighty-five percent of all BCCs appear on the head and neck region; 25% to 30% occur on the nose alone, the most common site. BCC is rarely found on the backs of the hands, although this site receives a significant amount of solar radiation. Tumors also occur in sites protected from the sun, such as the genitals and breasts. BCC in blacks is rare.
PATHOPHYSIOLOGY
BCCs arise from basal keratinocytes of the epidermis and adnexal structures (hair follicles, eccrine sweat ducts). Ultraviolet B (UVB) radiation (sunburn spectrum, 290 to 320 nm) is important for the induction of BCC. UVB radiation damages DNA and its repair system and alters the immune system. Depletion of ozone in the earth’s atmosphere results in higher levels of UVB radiation at the earth’s surface. Longer wavelength UVA radiation damages DNA and is also carcinogenic.
BCC grows by direct extension and appears to require the surrounding stroma to support its growth. This may explain why the cells are not capable of metastasizing through blood vessels or lymphatics. The course of BCC is unpredictable. BCC can remain small for years with little tendency to grow, particularly in the elderly, or it may grow rapidly or proceed by successive spurts of extension of tumor and partial regression.
BCC occurs at the site of previous trauma, such as scars, thermal burns, and injury. BCC occurs years later at sites treated with ionizing radiation. The tumor appears 3 months to 7 or more years later at the site of a well-remembered injury.
CLINICAL TYPES
BCC occurs in many different clinical forms, which vary in appearance and malignant potential.
Nodular BCC.
Nodular BCC is the most common form. The lesion begins as a pearly white or pink, dome-shaped papule resembling a molluscum contagiosum or dermal nevus. The mass extends peripherally. The lesion may remain flat. Traction on the surrounding skin accentuates the pearly border. Telangiectatic vessels become prominent and easily recognizable through the thin epidermis as the lesion enlarges. The growth pattern is irregular, forming an oval mass whereby the surface may become multilobular. The center frequently ulcerates and bleeds and subsequently accumulates crust and scale. Ulcerated BCCs were formerly designated rodent ulcers.
Ulcerated areas heal with scarring, and patients often assume their conditions are improving. This cycle of growth, ulceration, and healing continues as the mass extends peripherally and deeper; masses of enormous size may be attained. BCCs may present as nonhealing leg ulcers. Biopsy specimens should be taken of leg ulcers that do not respond to treatment. The tissue mass of a nodular BCC has a distinctive consistency that can be appreciated during curettage or biopsy. It has poor cohesive forces and collapses or breaks down when manipulated with a curette. This is an important diagnostic feature that supports the clinical impression during the biopsy procedure.
Pigmented BCC.
BCCs may contain melanin that imparts a brown, black, or blue color through all or part of the lesion. Clinically, the lesion resembles a melanoma or pigmented seborrheic keratosis, but close inspection reveals the characteristically elevated, pearly white, translucent border, and the biopsy confirms the diagnosis. The histologic pattern most frequently associated with pigment is the nodular pattern.
Management and risk of recurrence
There are several factors to consider before choosing the best treatment modality. The most important are clinical presentation, cell type, tumor size, and location.
Clinical type.
Nodular and superficial BCCs are the least aggressive and can be completely removed by electrodesiccation and curettage or by simple surgical excision.
Histologic type.
The micronodular, infiltrative, and morpheaform BCCs have a higher incidence of positive tumor margins (18.6%, 26.5%, and 33.3%, respectively) after excision and have the greatest recurrence rate. Clinically, BCCs with these patterns have poorly defined borders and are not apparent during physical examination. They subtly extend into surrounding tissue and are easily missed by blind treatment techniques such as surgical excision. An average of 7.2 mm of subclinical tumor extension was found in mopheaform BCCs in one study, compared with 2.1 mm of extension in well-circumscribed nodular lesions. Routine pathologic examination of surgically excised BCCs may not detect a small nodule or strand of BCC on the other side of the excision margin. These tumors need more aggressive treatment with wide excision or microscopically controlled surgery.
Tumor size.
In general, electrodesiccation and curettage afford excellent results for small (less than 2 cm) nodular BCCs located on the forehead and cheeks. Nodular BCCs on the forehead and cheek that are larger and have well-defined margins should be excised and closed; electrosurgery for large tumors may result in large, unsightly scars. The margins of sclerosing BCCs cannot be determined by inspection, and either excision or, preferably, Mohs’ micrographic surgery should be performed. Superficial BCCs of any size can be adequately removed by electrosurgery.
Location.
Tumors about the nose, eye, and ear require special consideration. BCCs of the medial canthus are particularly dangerous. The skin rests close to bone and cartilage, and tumor cells initially invade and proceed to migrate undetected along periosteum or perichondrium. Healing occurs over inadequately treated tumors, and deep invasion and lateral extension can remain undetected, resulting in a tumor of massive proportions. Extension to the eye and brain is possible.