Which of these is not a predisposing factor to the development of melanoma?
Pseudoxanthoma elasticum. Pseudoxanthoma elasticum is not a predisposing factor to the development of melanoma. It is a genetic disorder of elastic tissue involving skin, eyes and the cardiovascular system with no malignant potential. All the others can predispose to the development of melanoma. Acquired melanocytic naevi (MN) in Caucasian populations are important markers for the risk of melanoma development. The total number of MN on the whole body is the most important independent risk factor for melanoma and the risk of melanoma development increases almost linearly with rising numbers of MN (the average person has 20-40 acquired naevi).
With regards to cutaneous ‘horns’:
None of the above. Cutaneous horns may originate from well-differentiated squamous carcinomata (5-15%), but the majority are benign. They may warrant excision both on symptomatic grounds and to exclude malignancy.
The most common cancer of the ear is:
Squamous cell carcinoma (SCC).
Which is not a tumour known to commonly arise from a sebaceous (organoid) naevus?
Mycosis fungoides. This is not a tumour known to commonly arise from a sebaceous naevus. BCC is the most common malignant tumour, but benign tumours such as tricholemmoma, trichoblastoma and syringocystadenoma are much more common. Mycosis fungoides is a cutaneous T-cell lymphoma and is unrelated. Older series suggested malignant potential to be 10-15%, but more recent series suggest this rate is much lower. The tumours arise in adolescence or early adult life but can occur in children under 5 years.
Which statement is incorrect about Merkel cell tumour?
Is sometimes benign. This statement is incorrect; Merkel cell tumours are always malignant. They usually occur in the head and neck and they are an adenocarcinoma of neuroendocrine origin. Due to their high recurrence rates and radiosensitivity, postoperative radiotherapy is recommended.
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