Learning Objectives
Differentiate between Basal Cell Carcinoma (BCC), Squamous Cell Carcinoma (SCC), and Melanoma based on clinical presentation, risk factors, and histological markers. Master the ABCDE criteria for melanoma and the anatomical landmarks for facial carcinomas.
1. Non-Melanoma Skin Cancers (BCC & SCC)
These are the most common skin cancers, primarily driven by cumulative sun exposure. A high-yield distinction is their typical facial distribution.
| Feature | Basal Cell Carcinoma (BCC) | Squamous Cell Carcinoma (SCC) |
|---|---|---|
| Prevalence | Most common skin cancer. | 2nd most common. |
| Location | Above the upper lip (Face). | Below the lower lip, ears, and hands. |
| Appearance | Waxy, pearly nodules, telangiectasias, rolled borders. | Ulcerative red lesions; scaling plaques. |
| Associations | Sun exposure. | Immunosuppression, chronic wounds (Marjolin ulcer), arsenic. |
| Behavior | Locally invasive; rarely metastasizes. | May spread to the lymph nodes. |
2. Melanoma: The Deadly Skin Cancer
Melanoma has a high risk of metastasis. Prognosis is determined primarily by Breslow thickness (depth of invasion).
| Diagnostic Marker | Description / Association |
|---|---|
| ABCDE Criteria | Asymmetry, Border irregular, Color varied, Diameter > 6mm, Evolving. |
| Tumor Marker | S-100 (Neural crest origin). |
| Genetics | Activating mutation in BRAF kinase (V600E). |
| Acral Lentiginous | Type most common in people with darker skin tones (palms/soles). |
3. Pre-malignant and Related Lesions
Recognizing early changes can prevent progression to invasive carcinoma.
| Condition | Clinical Features | Risk |
|---|---|---|
| Actinic Keratosis | Small, rough, “sandpaper-like” erythematous papules. | Precursor to Squamous Cell Carcinoma. |
| Marjolin Ulcer | SCC arising in a chronic burn scar or non-healing wound. | Develops decades after the initial insult. |
Activity
High-Yield Mnemonics & Tips:
- BCC vs SCC: BCC is on the Brow (Upper lip/top). SCC is on the Smile (Lower lip/bottom).
- SCC Histology: Look for Keratin Pearls or intercellular bridges.
- Melanoma Treatment: Vemurafenib is a BRAF inhibitor (V600E mutation) used for metastatic melanoma.
- S-100: Melanocytes are neural crest derived, just like Schwann cells, so they share the S-100 marker.