Cryotherapy is commonly used to remove which of the following skin lesions:
# Malignant melanoma
#! Solar keratosis
# Keratosis pilaris
Explanation: Cryotherapy is suitable for small surface keratinocytic lesions. It should not be used to eradicate pigmented lesions that may be melanoma and is not often effective for dermal tumours. Keratosis pilaris is often a widespread genetic follicular abnormality and does not respond to cryotherapy.
Which of the following statements about cryotherapy are true?
#! The boiling point of liquid nitrogen is –196C
# The freezing point of liquid nitrogen is –196C
# A temperature of –10C ensures destruction of malignant cells
#! It may cause permanent hypopigmentation
Explanation: The boiling point of liquid nitrogen is -196C. A temperature of -30 to -50C at the base of a lesion is necessary to eradicate malignant cells.
Radiotherapy is sometimes used to treat:
#! Squamous cell carcinoma of the lip
#! A rodent ulcer in an elderly patient
#! Localised B-cell lymphoma
# Severe acute dermatitis
Explanation: Localised superficial X-rays are useful for treating keratinocytic tumours and lymphoma in elderly patients. Occasionally Grenz rays are recommended for chronic dermatitis and other inflammatory skin rashes.
Photodynamic therapy (PDT):
# Refers to treatment that uses a highly mobile light
#! May include intravenous or topically applied porphyrin derivatives
# Requires high intensity ultraviolet radiation
#! Can be used to treat in situ squamous cell carcinoma
Explanation: Photodynamic therapy (PDT) involves an oxygen-dependent phototoxic reaction and is used to treat superficial forms of non-melanoma skin cancer such as solar keratosis, in situ squamous cell carcinoma and superficial basal cell carcinoma. Porphyrin derivatives are applied topically or injected intravenously and after an interval, the tumour is exposed to high intensity visible light.
The following statements are true about laser light:
#! It is monochromatic, collimated and coherent
# Pulsed laser light causes more tissue destruction than continuous wave laser light
# Red light is often used to remove vascular skin lesions
#! Carbon dioxide lasers can be used to vaporise epidermal lesions
Explanation: Laser light is monochromatic, collimated and coherent. Pulsed laser light reduces transmission of heat to surrounding tissues so reduces tissue destruction. Yellow light is most often used for vascular lesions. Carbon dioxide laser vaporization is used to remove epidermal lesions and for facial resurfacing.