[106] Low Grade Fibromyxoid Sarcoma and Sclerosing Epithelioid Fibrosarcoma – A Clinicopathological Study of 15 Cases, Including Identification of 'Kinship' between These Two Sarcomas

B Rekhi, M Deshmukh, NA Jambhekar. Tata Memorial Centre, Mumbai, Maharashtra, India

Background: A morphological and lately, genetic resemblance in form of FUS rearrangements, has been identified in low grade fibromyxoid sarcoma (LGFMS) and hyalinizing spindle cell tumor with giant rosettes (HSCTGR). Few studies have also noted resemblance between LGFMS and sclerosing epithelioid fibrosarcoma (SEFS).
Design: We critically analyzed histomorphological features of 13 LGFMS cases and 2 SEFS cases, over 7 years, including identification of morphological similarity between these rare sarcomas. Two SEFS cases underwent FISH analysis for FUS rearrangement.
Results: Thirteen LGFMS cases, identified in 7 women and 6 men, had age range of 10-50 years (median =31 years), tumor (T) size varying from 2-16.5 cm (mean = 5.8 cms) and commonly occured in lower limb (6 cases). All cases showed variable, alternating myxoid & collagenous areas with spindle to polygonal cells and vascular arcades (11 cases). Mild (10 cases) to moderate atypia (3 cases); mitosis varying from nil (maximum cases) to 3/10hpf (1 case), intranuclear inclusions (5 cases), focal hyalinization (6 cases), perivascular hyalinization (6 cases), small / 'early' rosettes (6 cases), amianthoid fibres (3 cases) were noted. Four cases with giant collagenous rosettes were labeled as HSCTGR. SEFS-like areas were focally noted in 5 cases. On IHC, vimentin was consistently positive in all cases. MIB-1 ranged from 1-8% and was low in maximum cases. Three of 5 cases with wide excision have been free of disease (FOD) over 5-46 months. Other 7 excisions with unclear margins included 1 FOD, 1 metastatic & 1 recurrent case. Two SEFS cases occurred in thigh of 12 & 53 year old patients. The first case underwent wide excision for a 3.5 cm tumor; displayed focal vascular arcades and small rosettes, resembling LGFMS, in addition to 'classical' SEFS and was positive for FUS rearrangement. The other case was negative for FUS rearrangement. Both cases were of low-grade, showed mild atypia, no necrosis and low MIB-1 (1-2%).

Conclusions: Morphologic 'kinship' exists between LGFMS and SEFS. It is suggested that at least some SEFS cases form spectrum of LGFMS. Larger studies need to further validate this observation.
Category: Bone & Soft Tissue

Monday, March 22, 2010 11:30 AM

Platform Session: Section F, Monday Morning


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