Soft tissue
Fibroblastic / myofibroblastic tumors
Low-grade fibromyxoid sarcoma

Author: Raul Gonzalez, M.D. (see Authors page)
Editor: Jerad M. Gardner, M.D.

Revised: 26 August 2016, last major update April 2013

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Low-grade fibromyxoid sarcoma

Definition / General
  • Low-grade sarcoma with fibrous and myxoid areas, whorled growth pattern, low cellularity, bland fibroblastic cells and curvilinear or arcuate vessels
  • Also called Evans' tumor, hyalinizing spindle cell tumor with giant rosettes (Am J Surg Pathol 2003;27:1229) (a unique morphologic pattern seen in some low grade fibromyxoid sarcomas)
  • Likely closely related to sclerosing epithelioid fibrosarcoma, with case reports of same translocation (Am J Surg Pathol 2007;31:1387), cases with intermixed histology (Ann Diagn Pathol 2011:15:303), and both tumors often express MUC4 immunohistochemically (Am J Surg Pathol 2012;36:1444)
  • First described by Evans in 1987 (Am J Clin Pathol 1987;88:615); with increasing awareness, less rare than originally believed
Epidemiology
  • In trunk and deep extremities (thigh most common site) of young to middle-aged adults (median age 34 years, range 3 - 78 years), also intrathoracic (Hum Pathol 2008;39:623)
  • Rarely in retroperitoneum and mediastinum
  • Slight male predominance
Clinical Features
  • Prolonged preclinical stage
  • Slow-growing, painless soft tissue mass (1 - 18 cm)
  • Earlier studies suggested only a small subset metastasized, but a more recent study with long term follow up reported recurrence in 64%, metastasis in 45%, death from disease in 42%; patients with positive / uncertain margins more likely to have recurrence (up to 15 years later; median 3.5 years); metastases usually to lungs, pleura, chest wall (up to 45 years later; median 5 years, Am J Surg Pathol 2011;35:1450)
Radiology Description
Prognostic Factors
Case Reports
Treatment
  • Complete excision with wide margins
  • Resection of pulmonary metastases (metastasectomy) may be considered
  • Long term clinical follow up is prudent due to potential of very late recurrence or metastasis (decades after initial diagnosis)
Gross Description
  • Often 6 cm, well circumscribed, fibromyxoid cut surface, may be grossly infiltrative
Gross Images

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Tumor of falciform ligament



Well- circumscribed tumor of leg

Well- circumscribed tumor with giant rosettes

Low-grade fibromyxoid sarcoma

Figure 5

Micro Description
  • Low to moderately cellular, bland fusiform or spindled cells with focal to diffuse whirling in heavily collagenized stroma with abrupt transition to myxoid areas
  • 45% have epithelioid areas
  • 40% contain poorly formed but large collagen rosettes
  • Often infiltrates adjacent skeletal muscle
  • Occasionally has areas of increased cellularity, atypia, necrosis or mitotic activity characteristic of intermediate- to high-grade sarcoma
  • Recurrences may show increased cellularity and mitotic activity
Micro Images

Images hosted on PathOut servers:

The swirling growth pattern is storiform

Characteristic features include
fibrous and myxoid areas, a swirling
whorled growth pattern, low to
moderate cellularity and bland cells
with minimal nuclear pleomorphism

There is a relatively linear cell
arrangement in this area, but other
areas have the characteristic
swirling and whorled pattern



Images hosted on other servers:

Figure 6

Figure 7

Figure 8

Myxoid area showing arcades of blood vessels

Storiform pattern



Bland spindle cells in fibromyxoid stroma

Rosettes in spindled stroma

Covered by pelvic urothelium

Cells forming rosettes are PGP 9.5+, Factor XIII negative

Staining of vessels but not tumor by CD34, smooth muscle actin

Vimentin+



Courtesy of Mark Rodacker

Cytology Description
Cytology Images

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Figure 1

Figure 2

Figure 3

Figure 4

Positive Stains
Electron Microscopy Description
  • Fibroblastic differentiation
Electron Microscopy Images

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Rosette-forming cells have dense core granules

Figure 9

Molecular / Cytogenetics Description
Molecular / Cytogenetics Images

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Complex karyotype includes t(7;16)

Differential Diagnosis
  • Fibromatosis: usually lacks myxoid areas (sometimes can be myxoid though), fibrous cells are aligned in broad sweeping fascicles, straighter, cells appear more like reactive fibroblasts, distinct ectatic vessels present, diffuse or occasionally focal nuclear beta-catenin staining (Am J Surg Pathol 2005;29:653)
  • Fibrosarcoma: no myxoid component; "herringbone" fascicular pattern, a diagnosis of exclusion (Histopathology 2006;49:152) that should be made with much hesitation
  • Myxofibrosarcoma: more myxoid and less fibrous, more nuclear pleomorphism and hyperchromatism (contrast to LGFMS which is almost always bland and monomorphic with little to no pleomorphism), more developed vascular network, tumor cells aggregate around vessels (Histopathology 2004;45:29)
  • Myxoid neurofibroma: wavy nuclei, background of thick collagen bundles, S100+
  • Nodular fasciitis: tissue-culture histology, extravasated erythrocytes, myxoid cystic degeneration