Ocular Pathology

Anatomy and pathology of the human eye. Use it to review eye pathology for Ophthalmology Board Review or OKAP.

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Sunday, January 28, 2007

Osteoma of the Choroid (Osseous Choristoma)

Choroidal Osteoma
Definition: Benign choroidal tumor composed of mature bone that was described in 1978.
Incidence/ Prevalence: The tumor is quite rare. Shields reports only 61 patients in 26 years of practice.
Etiology: Uncertain, thought to be a choristoma; ~1/5 of the cases are however bilateral.
Clinical Findings: The typical presentation is that of a young (25 years is approximate mean age) white woman (at least 2/3 are in women) with a characteristic slightly elevated lesion that appears yellow to orange and has well-defined margins often with calcification in the juxtapapillary choroid. Choroidal osteomas typically enlarge slowly over many years. If the tumor involves the macula, vision is generally impaired. Subretinal neovascularization is a common complication of macular choroidal osteoma (~30%). Both choroidal osteoma and hemangioma may mimic a choroidal melanoma clinically and should, therefore, be included in the differential diagnosis of choroidal melanoma. About 1/5 of the cases are bilateral. The complication of neovascularization appears to be associated with decalcification of the tumor and visual loss.
Histopathology: A single clinicopathologic report has been published by Williams et al. and was mistaken for a melanoma. The tumor is composed of unremarkable-appearing compact bone located in the peripapillary choroid. The intratrabecular spaces are filled with a loose connective tissue containing large and small blood vessels, vacuolated mesenchymal cells, and scattered mast cells. The bone trabeculae contained osteocytes, cement lines, and occasional osteoclasts (expected with decalcification). The images we provide here show bone (number 1) in the choroid, but the clinical history was not known in the case. The overlying retina shows severe degenerative changes (arrow 2) and osteocytes are seen in lacunar spaces (arrow 3). A line showing the interface of calcified and non-calcified osteoid is evident (4). A hint of lamellae formation is seen especially to the right of number 3.
At higher magnification, one can appreciate the location in the choroid with adjacent melanocytes (number 6). The retinal pigment epithelium (number 5) is also visible in an adjacent section. The retina is detached (number 2). Note the absence of osteoblastic rimming.

Treatment: Some recommend laser therapy of neovascularization in small osteomas or osteomas with an enlarging rim, with the understanding that laser therapy may accelerate decalcification and that visual acuity after laser therapy is quite poor despite regression of the tumor. The rationale for treatment is if the tumor is small it is possible that the residual damage will be mitigated if treated when the lesion is tiny. There are reports of stabilization of a choroidal osteoma with transpupillary thermal therapy.
Prognosis: About half of the patients will lose vision and over half have poor visual acuity as the final outcome.


Shields et al
Shukla D et al

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