Case Study: October 2007

History

A 60-year-old male presents with a 4 month history of a yellow lump on his supero-temporal bulbar conjunctiva.

The lesion is sub-conjunctival and removed. Clinically it is thought to be abnormal fat.

The histology is shown in Figures 1, 2, 3 and 4.
Questions.

1. What is shown in Figures 3 and 4?

2. What is the diagnosis?

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1. Figures 3 and 4 show floret cells.

2. The diagnosis is subconjunctival herniated orbital fat, secondary to degenerative weakening of the orbital septum. This lesion has is confused for pleomorphic lipoma and well differentiated liposarcoma.

However, it lacks the aggregates of bland spindle cells and wiry collagen of pleomorphic lipoma and lacks the pleomorphic spindle cells in the fibrous septa of liposarcoma.

The floret cells are CD34 and vimentin positive and lack S100. These cells are reactive in nature and tend not to occur in normal orbital fat.

References.

Schmack I, Patel RM, Folpe AL, Wojno T, Zaldivar RA, Balzer B, Kang SJ, Weiss SW, Grossniklaus HE. Subconjunctival herniated orbital fat: A benign adipocytic lesion that may mimic pleomorphic lipoma and atypical lipomatous tumor.
Am J Surg Pathol. 2007 Feb;31(2):193-8.