Hi all,
I was asked by our orthopedic oncologist for my opinion on this 54M with
multiple bilateral masses of the face, axillae, neck and left periscapular
region. There are also several marrow replacing lesions in the spine and
both humeri.
The patient first noticed these masses in January 2020. The masses are
infiltrative in appearance. On MR they are low on T1, slightly high on STIR
and show enhancement. They are FDG avid. They have been biopsied multiple
times at an OSH showing fibroadipose tissue with fat necrosis, fibrosis and
lymphocyte infiltrate with no diagnosis of malignancy or any other
definitive diagnosis being made.
Would appreciate anyone’s input.
54M-with-multiple-soft-tissue-masses1.pptx 
Thanks to all of you who responded. The pathologist at our institution is
reviewing the slides from the OSH biopsy and I forwarded him the responses.
I’ll let you know if I hear anything new.
*1. fibromatosis x 2*
*2. Dercum disease x 3 *and IgG4-related disease (can get IgG immunstain on
path) +/- *brown fat/hibernomas *
3, Madelung disease or lipedema
4. Severe hydradenitis with medication related bone infarcts
5. Soft tissue form of myositis ossificans progressive without calcs
6. lymphoma (subQ panniculitis-like T cell lymphoma) which pathologically
not infrequently gets diagnosed as a benign entitiy given its bland
appearance
*7. panniculitis* (lupus panniculitis can affect the face like this but
rare and rarer in men).
Follow up path on this case. Open biopsy was performed of the left upper
back mass. Here are the path results.
Morphologically consistent with *Erdheim-Chester disease*; clinical
and radiographic correlation is required.
Note – The tissue is positive for BRAF mutation: (BRAF p.V600E or
p.V600D); refer to molecular pathology case MM21-172.
Microscopic description, with interpretation of immunoperoxidase
stains: sheets and clusters of foamy histiocytes, with rare Touton
giant cells (best appreciated in block A7), associated with dense
sclerosis, infiltrating into adipose tissue and skeletal muscle.
There are relatively sparse interspersed small lymphocytes and
plasma cells. Histiocytes are CD68+, CD163+, Factor XIIIA+,
Fascin+, CD1a-, langerin-, ALK1-, and are predominantly negative
for S100, with labeling seen in a small subset, only. Stain for
BRAF VE1 is technically-limited (noncontributory). GMS stain is
negative for fungi.