Pathology of Basal Cell Carcinomas (BCC)

BCC is the most common cancer in humans and the most common type of skin cancer
BCCs are believed to arise from hair follicle cells and are therefore found almost exclusively on hair-bearing skin
Most lesions are found on sun-exposed mask areas of the head and neck, but non–sun-exposed areas are also at risk
These tumors tend to grow slowly, but when untreated can lead to invasion of local structures including muscle, cartilage, and bone.
Although the biologic behavior of BCC is characterized by local and sometimes disfiguring invasiveness:
- Metastasis is rare, occurring in less than 0.05% of cases
There are multiple histologic subtypes of BCC, and subtype is predictive of its behavior:
- Less aggressive subtypes include:
  - Nodular BCC
  - Superficial BCC
  - Keratotic variant of BCC
  - Infundibulocystic variant of BCC
  - Fibroepithelioma of Pinkus
Higher-risk subtypes include:
- Sclerosing variant of BCC
- Infiltrating variant of BCC
- Micronodular variant of BCC
- Morpheaform (or desmoplastic) variant of BCC
- Basosquamous carcinoma
The higher-risk subtypes tend to have subclinical extension exceeding the visible borders of the lesion:
- Making treatment more difficult
Nodular BCC is the classic lesion of this type of non melanoma skin cancers (NMSC):
- It appears as a pink translucent nodule with rolled edges and is often described as “pearly”:
  - In dark-skinned individuals, these tumors are often pigmented and can resemble melanoma
- Overlying telangiectasias and ulceration are common:
  - They occur predominantly on the face

Superficial BCC:
- Is a variant that is more common on the limbs and trunk, and on other areas with little or no sun exposure:
  - It presents as a slow-growing, scaly pink plaque and can easily be confused with psoriasis, superficial SCC or SCC in situ (Bowen disease):
    - Gentle traction on the periphery of the lesion:
      - Often demonstrates a shiny translucent surface characteristic of BCC which can assist with diagnosis
The histologic subtype of BCC:
- Is highly predictive of its behavior
Less aggressive subtypes include:
- Nodular BCC
- Superficial BCC
- Keratotic variant
- Infundibulocystic variant BCC
- Fibroepithelioma of Pinkus
Higher-risk subtypes include:
- Sclerosing BCC
- Morpheaform BCC
- Infiltrative BCC
- Micronodular BCC
- Basosquamous carcinoma,
Nodular BCC:
- Which represents approximately 60% of cases:
  - Is the most common type
- It appears as a pink, translucent nodule with rolled edges:
  - Often described as “pearly”
- Overlying telangiectasias and ulceration are common
- BCCs:
  - Most commonly occur on the face (Head and Neck Region)
- Histologically, nodular BCC consists of:
  - Peripheral palisading of cells and chaotic arrangement of cells in the central region
The sclerosing variant:
- Has increased fibroblasts and the presence of fibrotic desmoplastic stroma