Light and electron microscopic findings in a patient with orbital myolipoma.
BACKGROUND
This report describes the pathology of myolipoma, which is a benign soft tissue tumor and is a very rare tumor of the orbit.


METHODS
A 41-year-old woman complained of exopthalmos of her right eye. By MRI (magnetic resonance imaging) examination, the tumor (30x20 mm) was located in the extraconus of four recti muscles. A part of the tumor was excised and examined with both light and electron microscopes and immunohistochemically.


RESULTS
Light microscopic inspection revealed the tumor was formed by spindle-shaped cells, which were adipocytes and smooth muscle. Electron microscopy showed the cytoplasm contained parallel filaments associated with fusiform densities. Immunohistochemical staining showed smooth muscle stained with SMA (smooth muscle actin). Angiomyolipoma was excluded by negative staining for HMB45, Melan A.


CONCLUSIONS
To our knowledge, only one case of orbital myolipoma has been reported. The intimate relationship between the two cell types led us to conclude that the tumor was dimorphic and could be classified correctly as a myolipoma.
Nagayama
Akiko
A
Department of Ophthalmology and Visual Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, 852-8501 Nagasaki, Japan.
Miyamura
Noritake
N
Lu
Zhongyang
Z
Tsuda
Yasuo
Y
Kitaoka
Takashi
T
Amemiya
Tsugio
T
Abe
Kuniko
K
D017667:Adipocytes / Q000473:pathology*; D000328:Adult; D005260:Female; D006801:Humans; D008067:Lipoma / Q000175:diagnosis / Q000473:pathology* / Q000648:ultrastructure; D008279:Magnetic Resonance Imaging; D008855:Microscopy, Electron, Scanning; D032389:Myocytes, Smooth Muscle / Q000473:pathology*; D009918:Orbital Neoplasms / Q000175:diagnosis / Q000473:pathology*; D012983:Soft Tissue Neoplasms / Q000175:diagnosis / Q000473:pathology*