Superficial Low-Grade Fibromyxoid Sarcoma

 Histologically and genetically identical to conventional deep LGFMS






Clinical Issues




• Appear to represent 10-20% of reported cases of LGFMS
• Often adults (typically 3rd-4th decade), but wide range

image Up to 1/3 arise in children and adolescents

• Most common in extremities (especially lower limb), buttock, and trunk

• Treatment: Complete surgical excision

• Better outcome reported than in deep forms of LGFMS

• Local recurrence uncommon; no metastases reported


Macroscopic




• Well-defined mass, most often in subcutis

• Median 4.2 cm (occasionally > 10 cm)


Microscopic




• Identical cytomorphologic features and spectrum as conventional LGFMS

• Variant morphology includes component of distinct collagen rosette-like structures


Ancillary Tests




• Diffuse MUC4(+) characteristic

• Rare focal or weak expression of CD34, EMA, or claudin-1

• Negative for keratins, S100, SMA, desmin

• Molecular: FUS rearrangements with CREB3L2 or CREB3L1


Top Differential Diagnoses




• Nodular fasciitis

• Fibromatosis

• Perineurioma

• Neurofibroma

• Cellular myxoma

• Dermatofibrosarcoma protuberans

• Myxofibrosarcoma

image
LGFMS
Low-grade fibromyxoid sarcoma (LGFMS) is classically characterized by admixed fibrocollagenous image and looser, myxoid image zones. Most cases arise in deep locations, but a minority occur superficially in the subcutis or less likely dermis.


image
Collagenous Zones in LGFMS
The collagenous zones of LGFMS tend to show relatively low cellularity, as depicted. On a limited biopsy, care must be taken to avoid misinterpretation as a benign process. Cytologically, the cells usually show mild to no atypia.

image
Myxoid Zones in LGFMS
The myxoid zones of LGFMS are often more cellular than the fibrocollagenous zones and tend to feature a more prominent stromal vasculature, as depicted here.

image
Hyalinizing Rosette-Like Structures
A distinctive morphologic variant of LGFMS contains a variable number of rosette-like structures with hyalinized collagenous cores image. These tumors were originally described as hyalinizing spindle cell tumor with giant rosettes.


TERMINOLOGY


Abbreviations




• Low-grade fibromyxoid sarcoma (LGFMS)


Synonyms




• Evan tumor

• Hyalinizing spindle cell tumor with giant rosettes

• Fibrosarcoma, fibromyxoid type


Definitions




• Subset of low-grade fibromyxoid sarcoma arising in dermis &/or subcutaneous tissue
image Histologically and genetically identical to conventional deep LGFMS


CLINICAL ISSUES


Epidemiology




• Incidence
image Appear to represent 10-20% of reported cases of LGFMS

image Probably underreported in literature

• Age
image Often adults (typically 3rd-4th decade) but wide range
– Up to 1/3 arise in children and adolescents

• Sex
image M > F


Site




• Most common in extremities (especially lower limb), buttock, and trunk

• Occasionally other sites


Presentation




• Usually slow-growing, painless mass

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Superficial Low-Grade Fibromyxoid Sarcoma
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