## **Core Concept**
Subungual melanoma is a type of skin cancer that occurs under the nails. It is a rare but aggressive form of melanoma. Early detection is crucial for effective treatment.

## **Why the Correct Answer is Right**
The correct answer, **Hutchinson's sign**, is a clinical sign associated with subungual melanoma. It is characterized by the discoloration (brown or black) of the nail plate and the surrounding tissues, including the nail fold. This sign indicates the spread of melanoma from under the nail to the adjacent tissues.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not correspond to a commonly recognized sign associated with subungual melanoma.
- **Option B:** This option is incorrect as it does not accurately represent a known clinical sign for subungual melanoma.
- **Option D:** This option is incorrect because it does not describe a recognized clinical feature of subungual melanoma.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl for subungual melanoma is to remember that **Hutchinson's sign** is a significant indicator of this condition. The presence of this sign necessitates further investigation, including biopsy, to confirm the diagnosis. Early recognition and biopsy are critical due to the aggressive nature of subungual melanoma.

## **Correct Answer:** . Hutchinson's sign.