Question

During the past several decades there has been an alarming increase in the incidence of skin cancers, including malignant  melanoma, that has been attributed to increased sun exposure.

1. Explain the possible mechanism whereby ultraviolet radiation promotes the development of malignant skin lesions.
2. Cite two important clinical signs that aid in distinguishing a dysplastic nevus from a malignant  melanoma

Answer 1

1. There are several steps which are responsible for malignant skin lesion formation. They are as follows -

A. The ultraviolet (UV) radiation increases the activity of cytokine receptors and also increases the level of cytokine which is responsible for uncontrolled cell proliferation.

B. UV can damage the DNA so mutation in genes of epidermal cells are very abundant. These mutation can inhibit the tumor suppressor genes such as p⁵³. Such mutation can also lead to the proto oncogene to oncogene conversation. Oncogenes are responsible for uncontrolled cell proliferation. Proto oncogenes are the cell cycle regulators.

C. For the DNA damage, the immune cells of epithelium are also hampered. They are are the responsible cells for conducting apoptosis to the tumor cells. So, proliferation of tumor cells become a continuous process.

2. Differences between dysplastic nevus and malignant melanoma are as follows -

Dysplastic nevus	Malignant melanoma
They are often under 5 millimetres	They are often wider more than 6 millimetres
The color may be mixture of tan, brown and red or pink shades	They are usually uneven in color, may have shades of black, brown and tan. Also have areas of white, pink, red, grey or blue
They have irregular or notched edges	They are often irregular and asymmetrical. Shape of one half does not match with the other
Surface texture may be smooth, slightly scaly, irregular and pebbly appearance	Surface texture may break down and looked scared, hard and lumpy, ooze or bleed
It rarely causes skin cancer	It is a type of skin cancer