Fatty metamorphosis and other patterns in fibrous dysplasia.
BACKGROUND
Interpretation of small biopsy fragments from suspected lesions of fibrous dysplasia with unusual clinical and/or radiological features may be challenging due to wide histomorphological spectrum of stromal appearances. Awareness of these variations should improve diagnostic confidence.


METHODS
We retrospectively studied 26 cases of fibrous dysplasia (F- 19, M- 7; Ages ranged from 10 to 53 years) with confirmed diagnosis. The sites of the lesions were skull bones (9), humerus (1), femur (8), tibia (2), fibula (3), talus (1), mandible (1), and maxilla (1).


RESULTS
Different stromal patterns, variably admixed with the classical pattern, were observed in 58%(15/26) of the cases. 20%(3/15) of these had more than one pattern. Focal fatty metamorphosis as groups of fat cells in the central portion of the lesion in the stroma of fibrous dysplasia between osseous trabeculae was observed in 23%(6/26) cases. Other patterns included myxoid stroma in 16%(4/26), collagenization of stroma in 12%(3/26), stroma rich pattern (with paucity of trabeculae) in 12%(3/26), foci of few foam cells in 23% (6/26), and calcified spherules in 12%(3/26). Focal osteoblastic rimming of trabeculae was observed only in 4%(1/26).


CONCLUSIONS
Various stromal variations and previously unreported fatty metamorphosis were frequently observed in fibrous dysplasia.
Shidham
Vinod B
VB
Dept of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA. vshidham@mcw.edu
Chavan
Ashwini
A
Rao
R Nagarjun
RN
Komorowski
Richard A
RA
Asma
Zeenath
Z
D017667:Adipocytes / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D001706:Biopsy; D002648:Child; D005260:Female; D005357:Fibrous Dysplasia of Bone / Q000473:pathology*; D006801:Humans; D006811:Humerus / Q000473:pathology; D007867:Leg Bones / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012886:Skull / Q000473:pathology*; D013628:Talus / Q000473:pathology