A rare developmental tumor, phakomatous choristoma (Zimmerman tumor) results from the aberrant retention of parts of the lens placode in the lower eyelid during embryologic development. As a result, lens epithelium proliferates within the inferonasal portion of the lower eyelid. The epithelial cells may undergo cytoplasmic enlargement, identical to the enlargement of “bladder” cells seen in posterior subcapsular cataract. Basement membrane material is produced, recapitulating the lens capsule (Fig 13-2); this material stains positively with periodic acid–Schiff (PAS) stain. The eyelid mass formed is usually present at birth and enlarges slowly. Complete excision is the usual treatment.
Figure 13-2 Phakomatous choristoma of the eyelid. The dermis displays a disorganized proliferation of lens epithelium (arrowheads) and occasional “bladder” cells (arrows) similar to those seen in posterior subcapsular cataract. Note the large amount of eosinophilic material, which represents lens crystalline proteins.
(Courtesy of Nasreen A. Syed, MD.)
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.