Which of the following is a sign of Cowden's disease?

Acral keratosis is indeed a sign associated with Cowden's disease, which is a genetic disorder characterized by multiple hamartomas and an increased risk of various cancers. Patients with Cowden's disease often present with skin lesions such as acral keratosis, which are thickened skin areas usually found on the palms and soles. This symptom is a key indicator of the condition and helps in clinical diagnosis.

In addition to acral keratosis, other signs can include facial trichilemmomas and mucosal lesions, but acral keratosis is a notable manifestation. The importance of recognizing acral keratosis in the context of Cowden's disease can guide further investigations for associated tumors, particularly breast and thyroid cancers, which are commonly viewed in these patients.

While thyroid carcinoma and other organ-related neoplasms may develop in patients with Cowden's disease, they are not signs specific to the condition in the same way that acral keratosis is. Liver tumors and pancreatic cysts are not characteristic features of Cowden's disease, further highlighting why acral keratosis is the correct answer associated with this genetic syndrome.