No, you cannot claim the contributions to a healthcare flexible spending account (FSA) as a medical expense.
The funds taken from your paycheck and deposited into your medical FSA are pre-tax funds. Since it is funded with money that has not been taxed, you cannot take a deduction for the contributions. The medical FSA amount is not required to be reported anywhere on your tax return and therefore it is not required to be shown on your W-2. You also should not report any medical expenses on your tax return that were paid or reimbursed with funds from the medical FSA.