Extra-abdominal desmoid fibromatosis
Swelling of the right upper arm with a slow increase in volume first noticed one year ago.
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The ROI is marked by a capsule stuck to the skin.
In the middle of the right upper arm in the subfascial space is an irregularly contoured structure with streaky extensions into the surrounding muscles and into the epifascial fat.
The signal is equal to muscular intensity in native T1 weighted series and with thoroughly high intensity in T1 C+. Just a lightly elevated signal in T2 weighted images and with high intensity in the PD weighted series.
Parts of a fibroblastic spindle cell lesion without significant cellular atypia. In immunohistochemistry, strong nuclear staining for b-catenin in the majority of spindle cells with partial positivity for desmin and SMA.
In the PCR analysis of the CTNNB1 gene (Exon 3) detection of a point mutation (c.121A>G; p.T41A).
Extra-abdominal desmoid fibromatosis.