Sarah Ferguson has said her skin cancer diagnosis was a "shock" and thanked well-wishers and medical staff for the support she has been given.
In a post on Instagram the Duchess of York, 64, said: "I have been taking some time to myself as I have been diagnosed with malignant melanoma, a form of skin cancer, my second cancer diagnosis within a year after I was diagnosed with breast cancer this summer and underwent a mastectomy and reconstructive surgery.
"It was thanks to the great vigilance of my dermatologist that the melanoma was detected when it was.
"Naturally another cancer diagnosis has been a shock but I'm in good spirits and grateful for the many messages of love and support."
She said she was "incredibly thankful" to her medical teams and added: "I believe my experience underlines the importance of checking the size, shape, colour and texture and emergence of new moles that can be a sign of melanoma and urge anyone who is reading this to be diligent."
"I am resting with family at home now, feeling blessed to have their love and support," she added.
The duchess was diagnosed with malignant melanoma, a form of skin cancer, after having several moles removed - with one of those identified as being cancerous.
Duchess 'proud of mastectomy'
Last year the duchess, the former wife of Prince Andrew, Duke of York, underwent an eight-hour single mastectomy operation and reconstruction after discovering she had an early form of breast cancer during a routine mammogram.
She previously said she had no symptoms and almost missed her appointment until her sister convinced her to go.
In a TV interview in December she said she was "proud" of her mastectomy and described it as a "badge of office".
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It comes after it was announced that the King is to attend hospital this week to be treated for an enlarged prostate.
What is malignant melanoma?
Malignant melanoma is a type of skin cancer that can spread to other parts of the body, according to the NHS website.
Its main cause is ultraviolet light, which comes from the sun and is used in sunbeds.
Symptoms include having a new mole or changes to an existing one, as well as large moles or those with uneven shapes or a mixture of colours.
The main treatment for the cancer is surgery, especially if it is caught early, but advanced melanoma can be difficult to treat.