What is the difference between melanoma, basal cell carcinoma, and squamous cell carcinoma?
Melanoma, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC) are the three most common types of skin malignancies, fundamentally differing in their cellular origin, clinical behaviour, aggressiveness, and metastatic potential. Melanoma originates from pigment-producing melanocytes and, although less frequent, is the most aggressive and dangerous type, as it can rapidly metastasise systemically to lymph nodes and distant organs even at an early stage. In contrast, basal cell carcinoma and squamous cell carcinoma are known as non-melanoma skin cancers (keratinocyte carcinomas). Basal cell carcinoma is the most common skin cancer; it grows slowly, can be locally invasive, but metastasises extremely rarely, resulting in negligible mortality. Squamous cell carcinoma arises from the more superficial keratinocytes of the epidermis, frequently develops from precancerous lesions (such as actinic keratosis), can be locally more aggressive than BCC, and carries a moderate potential to metastasise to regional lymph nodes and distant organs. Surgical excision is fundamental in the treatment of all three types; however, in advanced or metastatic cases, melanoma requires systemic immunotherapy or targeted therapy, whereas for unresectable BCC and SCC, specific targeted agents (such as Hedgehog inhibitors in BCC) or immunotherapy may play a role.
The cell of origin and biological characteristics of these tumours show marked differences: melanoma arises from melanocytes located in the basal layer, whereas basal cell carcinoma and squamous cell carcinoma are keratinocyte carcinomas resulting from the malignant transformation of keratinocytes. When examining matrix metalloproteinases (MMPs), it has been observed that the expression of MMP-3, MMP-9, and MMP-14 is intense in melanoma, reflecting the tumour's prominent invasiveness and angiogenesis, whereas in basal cell carcinoma, expression primarily serves local stromal remodelling, lacking metastatic potential.
In terms of incidence and prognosis, basal cell carcinoma accounts for the absolute majority of skin tumours, followed by squamous cell carcinoma, whereas melanoma is the rarer entity responsible for the highest mortality. In diagnostic and surgical approaches, dermoscopy is critical for all three to achieve clear-margin excision or Mohs surgery; in advanced tumours, melanoma frequently relies on BRAF or MEK inhibitors, as well as immune checkpoint inhibitors, whereas in extensive non-melanoma skin cancers, Hedgehog pathway inhibition or anti-PD-1 therapy represents a therapeutic option.
References
- Melanoma
- Melanoma: Pathogenesis and Targeted Therapy doi:10.1002/mco2.70566
- The Clinical Trial Landscape for Melanoma Therapies doi:10.3390/jcm8030368
- Global, regional and national burden of skin cancer from 1990 to 2021: Analysis of risk factors and prediction of trends in 2035. PMID 42410801
- Matrix metalloproteinase expression in basal cell carcinoma, squamous carcinoma, and melanoma: diagnostic and prognostic potential. PMID 42158425
- Skin Cancer: Diagnosis. PMID 42166763
- Non-surgical therapies for localized non-melanoma skin cancer in older adults: A review. PMID 42727392
- Basics of skin cancer: Types, diagnosis, and current challenges. PMID 42067315
- Skin Cancer: Screening and Prevention. PMID 42166762