Basal cell carcinoma: Clinical sciences

Basal cell carcinoma, or BCC for short, is the most common type of skin cancer. It develops on parts of the skin exposed to high levels of sunlight or ultraviolet radiation, such as the head, neck and the upper extremities.

BCC arises from basal cells, which are stem cells responsible for producing new skin cells. They are located in the deepest layer of the epidermis.

Most BCCs are slow growing, so they can go unnoticed for a long period of time, and they rarely metastasize. Treatment is based on risk of recurrence rate, and can be surgical or medical.

Alright, when a patient presents with a chief concern suggesting a BCC, the first step is to obtain a focused history and physical. Typically, patients notice a skin lesion that has been changing gradually in size or color, or one that won’t heal. Additionally, they might have risk factors like fair skin complexion and prolonged sun exposure. Patients may have a family history of cancers, or personal history of genetic disorders or immunosuppression.

Here’s a high yield fact! Xeroderma Pigmentosum is a rare autosomal recessive genetic condition characterized by impaired DNA repair mechanisms. When the UV rays from the sunlight cause damage to the skin cell DNA, the body is not able to repair the damage. As a result, these patients are at increased risk of developing skin cancers like BCC.

Now, on physical exam, you can expect to see a skin lesion that looks like a small raised bump or non-healing sore. The nodule can be translucent, shiny, waxy, or “pearly” in appearance, or it can appear as an ulcer with central depression and raised, rolled or elevated edges.

Occasionally, you might see surrounding telangiectasia, which is evidence of abnormal angiogenesis associated with skin malignancies.

In the late stages, BCCs can become quite large, with a fungating appearance indicating local invasion. These findings should lead you to suspect BCC.

The best way to confirm your diagnosis is to biopsy the lesion. Depending on the size, location, and appearance of the lesion, you can perform a punch, shave biopsy, incisional or excisional biopsy.

The biopsy results showing nests and island cells, peripheral palisading, fibrosis, clefting, increased mitotic activity, multinucleated cells or hyperchromatic nuclei, cystic spaces, ulceration or deep invasion into the subcutaneous tissue

These findings confirm your diagnosis of BCC. If biopsy findings are not consistent with BCC then consider an alternative diagnosis.

The three most common types of BCC are nodular, superficial, and infiltrative. Nodular BCC is the most prevalent subtype, comprising over 60% of cases. It usually presents with the classic raised, pearly, or waxy appearance with rolled edges. Some might have central ulceration.

Superficial BCC is the second most common, and often appears red and scaly. It can be difficult to differentiate it from other lesions like squamous cell carcinoma, eczema, or psoriasis.

On the other hand, infiltrative BCC are flat, white, scar-like in appearance. This is the most aggressive subtype of the three.

Other rare forms of BCC include morpheaform, micronodular, basosquamous, nodulocystic, follicular, infundibulocystic, neurotropic, and pleomorphic.