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Ossifying fibromyxoid
tumour
(OFMT)
presents as a well circumscribed small subcutaneous or muscular
nodule on the extremities.
Visit:
Myxoid Tumours of Soft Tissue
;
Soft
TissueTumours of Uncertain Differentiation ;
Neural tumours
;
Fibroblastic/Myofibroblastic tumours
;Myofibroblastic tumours
;
Myogenic tumours
;
ChondroOsseous tumours
Although
the tumour most commonly occurs on the extremities with a male
predominance, cases of OFMT have been reported in females, on the scalp
(occurring as a cystic lesion) , the nasal septum ( history of nasal
airway obstruction and enlargement contour of the nose) and in the orbit (
history of diplopia, pain, and right upper eyelid swelling).
This is an indolent tumour,
although local
recurrences may occur.
Line of differentiation of this tumour is uncertain, however it has been
suggested that the tumour is probably of partial neural, myoid or even of
myofibroblastic origin.
Microscopically, on the low power, the tumour is lobulated and an
incomplete shell of mature bone is note in the area corresponding to the
fibrous septa.
The tumour consists of lobules of uniform rounded cells
arranged in cords or strands. These cells are set in a fibromyxoid stroma. Mitotic figures are inconspicuous.
Unusual features include satellite micronodule formation, multiple
microcalcifications, epidermoid cysts and mucinous microcyst
formation, absence of myxoid areas, foci of atypical chondroid
differentiation, binucleate lacunar cells, pericytic growth pattern and
malignant change.
Atypical or malignant ossifying fibromyxoid tumour has been described by
Kilpatrick et al. The lesion is characterized by increased cellularity and
prominent mitotic activity. Some of these cases may metastasize to the
lungs.
Immunohistochemistry reveals that the tumour is positive with S100 protein
and vimentin. Many cases are desmin positive. Smooth muscle actin is
positive in about 50% cases. There is also focal reactivity for Leu7 and
GFAP.
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