Phakomatous choristoma (PC) is a benign congenital tumor consisting of ectopic lenticular tissue, typically presenting as a palpable mass at birth. It most commonly affects the lower eyelid nasally with inferomedial orbital extension.
Phakomatous choristoma was first described by Lorenz Zimmerman in 1971 as a rare benign congenital lesion composed of ectopic lenticular tissue. During normal development, the surface ectoderm invaginates to create the lens pit and subsequently the lens vesicle. It has been hypothesized that there is likely aberrant migration during this time with ectopic periocular growth of lenticular tissue, forming a PC tumor. As the skin of the eyelid is also of surface ectoderm origin, it is commonly affected as well.
PC is a pediatric tumor. In the 20 previously published reports, the age at time of surgical excision ranged from 2 weeks to 13 months, with an average age of about 5 months.
On H&E stain, histological features of PC resemble those of lens capsule, epithelium, and cortex. The lens capsule and epithelial islands can be highlighted on PAS stain. The use of IHC stains, including glial fibrillary acidic protein (GFAP), HMB45, synaptophysin, chromogranin, and others, has been reported in the literature, but they are not typically needed for diagnosis. These IHC stains may have been obtained to show that PC is derived from lenticular anlage as they were positive for vimentin, an intermediate filament normally found in lens epithelium; S-100 protein; and alpha, beta, and gamma crystallines, which are proteins specific to the crystalline lens.
PC typically presents as a firm palpable mass at birth, most commonly affecting the lower eyelid nasally with inferomedial orbital extension. There have been no reports of upper eyelid involvement.
A firm mass can be palpated on exam. Irregular eyelid contour and globe displacement may also be noted on exam. Tumor size has been reported to range from 10 mm to 17 mm in diameter, with many reports of enlarging tumors. There have also been several reports of PC inducing corneal astigmatism and anisometropia.
Definitive diagnosis of PC requires histological studies. PC is thought to be of lenticular origin, which has been supported by the tumor’s histological and immunohistochemical resemblance to lens tissue. Histopathological findings of pseudoglandular structures and aggregates of cuboidal epithelial cells surrounded by a thick basement membrane share similarities to the cortex of normal and cataractous lenses. Diagnosis of PC is made with routine H&E stain showing histological features resembling lens capsule, epithelium, and cortex. If diagnosis remains unclear, a referral to an ophthalmic pathologist may be made.
MRI and CT imaging are not required for diagnosis. However, they may be useful for distinguishing PC from other periocular and orbital lesions.
The differential diagnosis of PC includes other pediatric periocular tumors, such as dermoid cyst, hemangioma, neurofibroma, dacryocele, and rhabdomyosarcoma.tumor On imaging, PC has been described as a solid, well-circumscribed, and contrast-enhancing mass. PC does not typically have calcifications or fat content as seen with dermoid cysts and does not have vascular contrast patterns as seen with hemangiomas. In addition, PC rarely involves the lacrimal sac and nasolacrimal duct, differentiating it from dacryoceles which are exclusively found in the lacrimal system. Unlike malignant periocular lesions, PC does not cause bony erosions or necrosis.
Surgical excision of the tumor is curative. No reports of spontaneous resolution and no known medical treatments exist to date. Prompt recognition and surgical intervention of PC may be warranted as the risk of astigmatism can cause amblyopia.
Surgical follow up
There have been no reports of recurrence in the literature, with follow-up times ranging from a few weeks to 7.5 years. Even in cases in which the tumor was incompletely excised, there was no recurrence nor residual ocular abnormalities. Apart from postoperative follow up, long-term surveillance is not necessary given the benign clinical nature of PC.
- ↑ 1.0 1.1 1.2 Zimmerman LE. Phakomatous choristoma of the eyelid. A tumor of lenticular anlage. Am J Ophthalmol. 1971;71(1 Pt 2):169–177.
- ↑ 2.0 2.1 Jung EH, Avila SA, Gordon AA, de la Garza AG, Grossniklaus HE. Phakomatous Choristomas: A Case Report and Review of Literature. Ophthalmic Plast Reconstr Surg. 2022 Jul-Aug 01;38(4):330-335.
- ↑ Rafizadeh SM, Ghadimi H, Nozarian Z. Phakomatous choristoma of the eyelid and orbit: a case report. Pediatr Dev Pathol. 2020;23:296–300.
- ↑ Ellis FJ, Eagle RC Jr, Shields JA, et al. Phakomatous choristoma (Zimmerman’s tumor). Immunohistochemical confirmation of lens-specific proteins. Ophthalmology. 1993;100:955–960.
- ↑ McMahon RT, Font RL, McLean IW. Phakomatous choristoma of eyelid: electron microscopical confirmation of lenticular derivation. Arch Ophthalmol. 1976;94:1778–1781.
- ↑ Romano RC, McDonough P, Salomao DR, et al. Phakomatous choristoma in a 10-week-old boy: a case report and review of the literature. Pediatr Dermatol. 2015;32:405–409.
- ↑ Harris BF, Harris JP, Ducey TJ, et al. Phakomatous choristoma of the orbit with involvement of the inferior oblique muscle. Ophthalmic Plast Reconstr Surg. 2019;35:e10–ee9.
- ↑ Shin HM, Song HG, Choi MY. Phakomatous choristoma of the eyelid. Korean J Ophthalmol. 1999;13:133–137.