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RE: Bilateral subconjunctival masses due to orbital fat prolapse

      A 41-year-old male presented with 6 months of bilateral symmetrical subconjunctival lesions that appeared after a motor vehicle collision (Fig. 1) . Injuries included a unilateral zygomatic fracture repaired without incision around the orbit. Ocular examination revealed a visual acuity of 20/20 OU and bilateral, soft, yellow masses in the temporal bulbar conjunctiva which were easily displaced posteriorly with a cotton-tipped swab. Computed tomography disclosed continuity of both subconjunctival lesions with the intraconal space. Both masses were excised without complication.
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      Fig. 1Presentation with bilateral symmetrical conjunctival masses (arrows).
      Both masses had a similar histologic appearance of uniform hypovascular lobules containing mature adipocytes separated by fibrovascular septa (Fig. 2) . Focal areas showed increased cellularity, including inflammatory cells and frequent multinucleated giant cells within fibrous septa with their nuclei arranged in a “floretlike” pattern (Fig. 2, inset).
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      Fig. 2Subconjunctival mass shows typical prolapsed orbital fat, with uniform hypovascular lobules, and fibrous septa (H&E 100×). Inset: high power view of a multinucleated, “floretlike” giant cell in the fibrous septum of the prolapsed orbital fat (H&E 640×).
      Orbital fat is divided into 2 compartments: extraconal fat lies outside the extraocular muscles and Tenon's capsule, whereas intraconal fat lies within the extraocular muscle cone.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      • Ebrahimi K.B.
      • Ren S.
      • Green W.R.
      Floretlike cells in in situ and prolapsed orbital fat.
      Various mechanisms (e.g., trauma, surgery, degeneration) can lead to disruption of the connective tissue support of orbital fat leading to herniation.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      Unlike the more common extraconal fat prolapse frequently seen as an aging change, intraconal fat prolapse is rarely reported.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      • Ebrahimi K.B.
      • Ren S.
      • Green W.R.
      Floretlike cells in in situ and prolapsed orbital fat.
      • McNabb A.A.
      Subconjunctival fat prolapse.
      • Kim Y.D.
      • Goldberg R.A.
      Orbital fat prolapse and dermolipoma: two distinct entities.
      Intraconal fat prolapse may be unilateral, or bilateral in one-third of cases, and generally is located superiorly and temporally, as in our case, secondary to the thin intermuscular septum and abundant fat in this region.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      • McNabb A.A.
      Subconjunctival fat prolapse.
      Intraconal fat prolapse may be confused clinically with dermolipoma, conjunctival lymphoma, and lacrimal gland prolapse.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      • McNabb A.A.
      Subconjunctival fat prolapse.
      • Kim Y.D.
      • Goldberg R.A.
      Orbital fat prolapse and dermolipoma: two distinct entities.
      However, it can be distinguished by the ease with which it can be pushed posteriorly, and also histopathologically. CT and MRI may identify fat prolapse by demonstrating continuity with the intraconal space, as in our case.
      • Ebrahimi K.B.
      • Ren S.
      • Green W.R.
      Floretlike cells in in situ and prolapsed orbital fat.
      • Kim Y.D.
      • Goldberg R.A.
      Orbital fat prolapse and dermolipoma: two distinct entities.
      Recently, there has been confusion and debate concerning the differentiation between intraconal fat prolapse and pleomorphic lipoma.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      • Ebrahimi K.B.
      • Ren S.
      • Green W.R.
      Floretlike cells in in situ and prolapsed orbital fat.
      • Daniel C.S.
      • Beaconsfield M.
      • Rose G.E.
      • et al.
      Pleomorphic lipoma of the orbit: a case series and review of the literature.
      Pleomorphic lipoma is a rare subtype of lipoma most often seen in the soft tissues of the head and neck, on a morphologic continuum with spindle cell lipoma.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      • Daniel C.S.
      • Beaconsfield M.
      • Rose G.E.
      • et al.
      Pleomorphic lipoma of the orbit: a case series and review of the literature.
      In 2003, Daniel et al.
      • Daniel C.S.
      • Beaconsfield M.
      • Rose G.E.
      • et al.
      Pleomorphic lipoma of the orbit: a case series and review of the literature.
      published a series of 6 cases believed to represent pleomorphic lipoma of the orbit. Histopathological features of these cases included large multinucleated cells often arranged in a “floretlike” pattern. Although thought to represent a distinguishing feature of pleomorphic lipoma and other neoplasms, similar cells, but usually with small normochromatic nuclei, have been recently identified in both prolapsed and in situ intraconal orbital fat, suggesting they also may result from a reactive or degenerative process.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      • Ebrahimi K.B.
      • Ren S.
      • Green W.R.
      Floretlike cells in in situ and prolapsed orbital fat.
      As immunohistochemical markers have not been shown to differentiate orbital fat from pleomorphic lipoma, recently proposed diagnostic criteria for pleomorphic lipoma include wire-like collagen and hyperchromatic multinucleated cells and pleomorphic spindle cells located within fat rather than within fibrous septa.
      • Schmack I.
      • Patel R.M.
      • Folpe A.L.
      • et al.
      Subconjunctival herniated orbital fat: a benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
      • Ebrahimi K.B.
      • Ren S.
      • Green W.R.
      Floretlike cells in in situ and prolapsed orbital fat.
      In summary, we report a case of bilateral, symmetric intraconal fat prolapse. The relative rarity of intraconal fat prolapse has led to concern over the correct diagnosis of these lesions. Despite recent clarification of the histopathologic distinction between orbital fat prolapse and pleomorphic lipoma, the rarity of both entities necessitates careful clinical and histopathologic assessment of all suspected cases.

      References

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