Bone Located Centrally Within a Dermolipoma

Elsas and Green¹ defined a dermolipoma as "a congenital, choristomatous tumor containing dermis-like connective tissue and adipose tissue; it was usually covered by nonkeratinized, or less commonly by keratinized squamous epithelium." On pathologic study, bone has been found adjacent to excised dermolipomas in several reports.^2-4 In an article by Eijpe et al⁵ on the characteristic appearance of dermolipomas on computed tomography (CT) scan, the authors did not find calcification in any of their 10 reported cases.⁵ We report the clinical, CT scan, and pathologic findings of a patient with bone located centrally within, rather than adjacent to, a pedunculated dermolipoma.

At birth, a mass was noted at the left lateral canthal area in an otherwise healthy girl. The mass reportedly remained the same size relative to her eyelid and facial structures as she grew. When she was 6 months old, her pediatrician obtained a CT scan of the orbits. The CT scan showed a cystic area with low density similar to fat at the left lateral canthal angle. Centrally within the cystic area was a high-density round mass. The orbital bones were normal(Figure 1).

We evaluated the patient when she was 7 months old. At her left lateral canthus was a soft, mobile, 7 × 7-mm, external pedunculated yellow-tinged mass covered by skin. The external mass was contiguous with a 7 × 5-mm, soft, yellowish subconjunctival mass (Figure 2). The eyelids and eyelid fissures were symmetric, with good lateral tendonous support. The orbital rims were normal. No lesions or deformities were present in the preauricular or auricular areas. Her ocular motility was full, and she had no strabismus. There was no globe displacement, and retropulsion was soft. Her corneas and tear films were normal. Her intraocular examination results were normal.

Her parents requested surgical excision of the mass when she was 14 months old. The mass lesion and her ocular examination findings were unchanged. The entire external portion of the mass and the anterior portion of the contiguous subconjunctival mass were excised.

Histopathologic examination of the excised tissue revealed a typical dermolipoma that was lined by squamous epithelium and contained pilosebaceous structures and adipose tissue. In the center of the dermoid, there was a round area of compact bone with hematopoietic bone marrow in the center (Figure 3).

In a survey of 282 epibulbar tumors in children, Cunha et al⁶ reported 15 dermalipomas. They did not mention any bone formation in these lesions. They did report one case of an epibulbar osseous choristoma and one case of a choristoma composed of cartilaginous tissue.⁶ Fry and Leone⁷ reported on 45 excised dermolipomas. Three of their cases had osteoma formation, but no further information was given.⁷ Hered and Hiles² described an osseous lesion overlying the sclera that was beneath and separate from a dermolipoma. Ferry and Hein⁸ excised a right outer canthus dermoid, and on microscopic examination, an osseous choristoma was found at the base. The bone was separated from the fat by dense connective tissue.

Daicker and Perren³ described a left superior temporal dermolipoma that after excision on histopathologic study was found to have a small plate of bone. The inferior surface of the bone was concave, and the opposite face was convex.³ The shape of the bone would suggest an epibulbar or episcleral osteoma. Marback et al⁹ described a pedunculated epibulbar mass anterior to the right lateral rectus associated with a right eye retinoblastoma. The CT scan revealed foci of calcification in the retinoblastoma and calcification of the epibulbar lesion. The pathologic examination revealed an intraocular, well-differentiated retinoblastoma without extraocular extension, and a separate epibulbar mass with osseous tissue mixed with fat tissue and dense collagen that they considered an osseous choristoma.⁹ Gayre et al¹⁰ reported on an epibulbar osseous choristoma associated with fibrovascular connective, adipose, andlacrimal tissues, but no radiologic studies were described. Gonnering et al⁴ described 2 cases that, clinically, were initially felt to represent dermolipomas. One was excised and shown to have bone adherent to the sclera. Their other case, on CT and echography scans, showed a high-density mass adjacent to, or part of, the sclera.⁴

The CT scan of our case revealed that the bone was located within the central portion of the dermolipoma, and histopathologic examination confirmed this. This seems to be in contrast with other cases that suggest that the bone was present in an epibulbar or episcleral location at the base of the lipodermoid. Eijpe et al⁵ found no bone or calcification on CT scans in their 10 cases of dermolipomas. Their microscopic examinations also did not reveal any bone in the specimens.⁵ Our case's pathological examination and CT scan results support each other in demonstrating osseous changes centrally within the lateral canthal pedunculated choristomatous dermolipoma.

The authors have no relevant financial interest in this article.

Corresponding author and reprints: Gary S. Lissner, MD, Department of Ophthalmology, 15th Floor, Northwestern Medical Faculty Foundation, 675 N St Clair, Chicago, IL 60611 (e-mail: glissner@nmff.org).