Moles (nevi) are the most common neoplasms of the skin. About one nevus in a million can turn into a malignant melanoma, and about 50% of melanomas derive from a nevus. One must suspect malignant development with change of colour (turning uneven or black), irregular and reddening edging, itching, and bleeding.
Both squamous cell carcinoma and malignant melanoma can be triggered by external influence. Ultraviolet radiation plays the dominant role. Consequently, there is an increased occurrence in seafarers and fishermen that work on the deck of both of these cutaneous malignancies35,36. In 60% of the fishermen a physical examination of was able to identify actinic keratoses, which are regarded as premalignant conditions that may eventually progress to carcinoma. The presence of basal and squamous cell carcinoma has been demonstrated in 9% and 6% of fishermen, respectively.5
Excess solar radiation also accounts for an increased prevalence of squamous cell carcinoma of the lip in fishermen37 and seafarers.35 Seafarers with previous dermatological cancers and continued solar exposure should be controlled for recurrence and advised accordingly.38