Basal Cell Carcinoma vs Squamous Cell Carcinoma
Basal cell carcinomas and squamous cell carcinomas are both skin cancers. Therefore, the both are epithelial cancers. They can appear at any site on the skin, but evidence show that there is a higher risk at sun exposed areas. All cancers are thought to have a common mechanism of origin. Cancers are thought to be due to abnormal genetic signaling which promote uncontrolled cell division. There are genes called proto-oncogene, with a simple alteration, which can be cancer causing. Mechanisms of these alterations are not clearly understood. Two hit hypothesis is an example of such a mechanism. There are many risk factors for skin cancer. Ultra violet light, tobacco, human papillomavirus (HPV), ionizing radiation, low immunity, and congenital conditions like congenital melanocytic nevi syndrome are some of the known causes of skin cancer. Distant sites containing fragments of cancer are called metastatic sites. Liver, kidneys, prostate, vertebral column, and brain are a few well known sites to which cancer can spread. These facts and figures apply to squamous cell cancers and basal cell cancers too. According to cancer invasiveness, spread, and general patient outcome, both types need supportive therapy, radiotherapy, chemotherapy, surgical excision for the cure, and palliation. Besides these similarities, from the cellular origin onwards, there are many differences between squamous cell carcinoma and basal cell carcinoma, which are discussed below in detail.
Squamous Cell Carcinoma
Squamous cells epithelium is found on skin, anus, mouth, small airways, and a few other places. Rapidly dividing and renewing tissues are more susceptible to cancers. These cancers are, therefore, found in areas covered with squamous cells. These cancers are very visible and should not be missed. Squamous cell cancers present as ulcers with hard, raised edges. These cancers may begin as abnormal pigmentation, scar tissue, and simple wounds. Long standing non healing ulcers with rapidly dividing marginal cells may turn into squamous cell cancers. It is found commonly on lips of smokers. These cancer cells rarely spread with blood and lymph flow. However, there may be extensive destruction of local tissues.
Squamous cell cancers may be confused with keratoacanthoma. Keratoacanthoma is a fast growing, benign, self-limiting raised lesion with keratin plugging. Examination of a wound edge biopsy under the microscope may show cancer cells. Following diagnosis, total local excision is mostly curative.
Basal Cell Carcinoma
Basal cell cancers are commonly seen in sun exposed areas of skin. They present as pearly, pale, smooth and raised patches. Head, neck, shoulders and arms are mostly affected. There is telangiectasia (small dilated blood vessels within the tumor). There may be bleeding and crusting giving an impression of a non-healing ulcer. Basal cell cancers are the least deadly of all skin cancers, and it is completely curable with proper treatment.
Image 1: Squamous Cell Carcinoma Image 2: Basal Cell Carcinoma
What is the difference between Basal Cell Carcinoma and Squamous Cell Carcinoma?
• Basal cell carcinoma arises from the deepest actively dividing layer of cells while squamous cell cancers arise from differentiated cells in upper layers of the skin.
• Squamous cell carcinoma is less common than basal cell cancers.
• Squamous cell cancers spread more rapidly and frequently than basal cell cancers.Image Source: Image 1: http://visualsonline.cancer.gov/details.cfm?imageid=2165 Image 2: Own work, Author: James Heilman, MD)