Melanoma in Situ
An early-stage melanoma confined entirely to the epidermis with no invasion of the dermis, also referred to as stage 0 melanoma.
Full Definition
Melanoma in situ (MIS) represents the earliest recognisable form of melanoma, in which malignant melanocytes proliferate within the epidermis but have not breached the basement membrane. Lentigo maligna is the most common subtype of melanoma in situ on chronically sun-damaged skin. The Latin phrase 'in situ' (meaning 'in place') should not be italicised in standard clinical documentation and should not be hyphenated. Editors must distinguish this from invasive melanoma, which carries a significantly different prognosis and staging.
Usage
Usage note: 'In situ' is written as two unhyphenated words and is not italicised in clinical text per most style guides. Capitalise 'Melanoma' only at the start of a sentence.
In Context
- "Excision with 5 mm margins was recommended following the diagnosis of melanoma in situ on the left cheek." — Dermatology surgical plan
- "Melanoma in situ carries an excellent prognosis when excised with clear margins." — Patient information leaflet