Ossifying fibromyxoid tumor

Soft tissue

Fibroblastic / myofibroblastic

Authors: Ashley Gullett, M.D., Jerad M. Gardner, M.D.

Topic Completed: 1 June 2013

Minor changes: 10 September 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: Ossifying fibromyxoid tumor [title]

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Table of Contents

Cite this page: Gullett A. Ossifying fibromyxoid tumor. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/softtissueossifyingfibromyxoid.html. Accessed October 25th, 2020.

Definition / general

Extremely rare mesenchymal tumor of intermediate malignancy and uncertain line of differentiation; characterized by peripheral metaplastic bone and cords of bland, round cells in a fibromyxoid matrix (Stanford University)
First described in 1989 (Am J Surg Pathol 1989;13:817), now 300+ cases reported (Am J Surg Pathol 2008;32:996)

Clinical features

Adults, median age 50 years (range 14 - 83 years), no sex predilection
Presents with small painless mass, most commonly lower extremity, but in any soft tissue location including head and neck
Usually histologically benign with benign clinical course; local recurrences in 17%, malignant behavior in 5%
Histologically malignant OFMTs are high-grade sarcomas with distant metastases and adverse outcome in up to 60% of patients
May have neuroectodermal origin due to CD56+, CD99+ (Int J Surg Pathol 2007;15:437, Am J Surg Pathol 2011;35:1615)

Radiology images

Contributed by Mark R. Wick, M.D.

CT, chest wall

Prognostic factors

Poor prognostic factors: high cellularity, high nuclear grade, > 2 mitotic figures / 50 HPF (Am J Surg Pathol 2003;27:421)

Case reports

21 year old woman with gingival mass (J Periodontol 2009;80:687)
56 year old man with 5 cm thigh mass ( Case of the Week #348)
73 year old male with left scapular mass (BMJ Case Rep 2011 Mar 24;2011)
Invasive spinal tumor (Skeletal Radiol 2008;37:1137)

Treatment

Excision

Gross description

Well circumscribed, median 4 cm, usually involves deep soft tissue, also cutaneous (Am J Dermatopathol 2007;29:156) or subcutaneous (J Cutan Pathol 2006;33:749) with radiographically apparent shell of bone

Microscopic (histologic) description

Nests / cords of round / oval cells, primarily epithelioid, with indistinct cytoplasm in fibromyxoid to hyalinized matrix
Lobulated at low power
Surrounded by partial shell of lamellar and woven bone and collagenous pseudocapsule
Minimal atypia and minimal mitotic figures, but may have necrosis, vascular invasion or high nuclear grade

Microscopic (histologic) images

Contributed by Mark R. Wick, M.D.

Various images

Case #348

56 year old man

Images hosted on other servers:

Occipital scalp lesion

Cytology description

Clusters, cords or small aggregates of round, polygonal or spindle cells in myxoid background with osteoid-like material (Diagn Cytopathol 2004;30:41)
Malignant cases may show significant nuclear pleomorphism with coarse chromatin, irregular contours and 1 - 2 distinct nucleoli (Acta Cytol 2001;45:745)

Positive stains

S100 (73%), desmin (38%), cytokeratin (11%), EMA (16%), SMA (6%), INI1 (lost in mosaic pattern in 74%), MUC4 (21%), neurofilament (80%), CD56 (43%) (Am J Surg Pathol 2011;35:1615)

Negative stains

Alpha smooth muscle actin (usually, may be weak, J Laryngol Otol 1993;107:75)

Electron microscopy description

Complex cell processes, reduplicated basal lamina (Ultrastruct Pathol 2007;31:233)

Molecular / cytogenetics description

Cytogenetics: PHF1 gene rearrangement (6p21) (Am J Pathol 2012;181:1069); monosomy 22 can be found in malignant form; may also have complex aberrations (Cancer Genet Cytogenet 2007;176:156, Cancer Genet Cytogenet 2002;133:124)
Molecular: INI1 gene deletion via FISH in 71% (Am J Surg Pathol 2011;35:1615)