A man with Pancoast tumor developed Horner's syndrome. All of the following are the features of Horner's syndrome, EXCEPT:

Horner's syndrome consists of unilateral enophthalmos, ptosis, miosis, and loss of sweating over the ipsilateral half of the face or forehead (anhidrosis). It is caused by ipsilateral involvement of the sympathetic pathways in the carotid plexus, the cervical sympathetic chain, the upper thoracic cord, or the brain stem. Melanocyte maturation in the iris depends on sympathetic innervation; thus, a less pigmented (bluer) iris occurs in congenital or longstanding acquired Horner's syndrome. Ref: Riordan-Eva P., Hoyt W.F. (2011). Chapter 14. Neuro-Ophthalmology. In P. Riordan-Eva, E.T. Cunningham, Jr. (Eds), Vaughan & Asbury's General Ophthalmology, 18e.