That statement is far too broad.

Acanthosis nigricans can, in rare circumstances, occur as a paraneoplastic sign, meaning it is associated with an underlying malignancy. This form is sometimes called malignant acanthosis nigricans.

However, the vast majority of acanthosis nigricans cases are not caused by cancer.

The more common causes include insulin resistance, obesity, type 2 diabetes, and certain endocrine or medication-related conditions.

Malignancy-associated acanthosis nigricans is uncommon and tends to have a different clinical pattern.

Doctors may become more concerned when the skin changes appear suddenly, progress rapidly, become unusually extensive, or occur in unusual locations, particularly in an older adult without an obvious metabolic explanation.

The changes may also involve areas beyond the typical neck and armpits.

Another unusual feature can be involvement of the lips or oral mucosa.

In some cases, the skin changes may occur together with other symptoms that require investigation.

Certain internal cancers have been associated with malignant acanthosis nigricans, with gastrointestinal cancers among the malignancies reported in medical literature.

But the presence of acanthosis nigricans alone does not tell a doctor that cancer is present.

Doctors consider the entire clinical picture, including age, medical history, speed of onset, physical examination, risk factors, associated symptoms, and laboratory findings.

If the presentation is unusual or there is no obvious explanation, additional investigations may be appropriate.

This distinction is extremely important because frightening health headlines can cause unnecessary anxiety.

A dark patch on the neck does not mean someone has cancer.

At the same time, an unusual and rapidly developing skin change should not automatically be dismissed.

The correct response is neither panic nor neglect.

It is appropriate medical evaluation.

A healthcare professional can determine whether the appearance is consistent with acanthosis nigricans and then consider what underlying condition, if any, may be contributing to it.

Chapter 4: Other Warning Signs That Deserve Attention

The appearance of darkened skin is only one piece of the puzzle.