Rash on the neck

33 y, African-American woman with h/o HTN and morbid obesity, s/p gastric bypass surgery 6 months ago and subsequent weight loss of 100 lbs, presents to the office for a routine follow up. Since the surgery, her HTN has resolved and she is off all her medications.
On exam, her vital signs were stable. Head and neck exam shows graying plaques with prominent skin lines on the nape of the neck. Which of the following statements is false?

1. The skin pathology is associated with PCOS, DM, Cushing’s syndrome, hypothyroidism and acromegaly.
2. Rapid development of this lesion with involvement of palms/ soles and mucous membrane is suggestive of underlying GI malignancy
3. Metformin and Rosiglitazone have not been effective in treatment of this pathology.
4. Skin biopsy needs to be done to rule out melanoma
5. Treatment of the underlying cause is most definitive.