Soft tissue
Uncertain differentiation

Topic Completed: 1 November 2012

Minor changes: 15 September 2020

Copyright: 2002-2020,, Inc.

PubMed search: Myxoma [title] soft tissue "loattrfree full text"[sb]

Vijay Shankar, M.D.
Page views in 2019: 15,049
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Cite this page: Shankar V. Myxoma. website. Accessed September 23rd, 2020.
Definition / general
  • Rare, benign, gelatinous lesion resembling fetal umbilical cord; often deep within muscle of extremity (Stanford University)
  • May derive from modified fibroblasts
  • Not a WHO diagnosis
  • Thigh, shoulder, upper arm
Clinical features
  • Diagnosis less likely if any of these findings: atypia, mitotic activity, more than occasional vessels, not intramuscular or juxtaarticular
Case reports
  • Excision; rarely recurs if adequately excised
  • Cellular cases appear to have same indolent behavior if completely excised (Histopathology 2001;39:287)
Gross description
  • Mucoid / gelatinous, often poorly circumscribed, may have infiltrative borders
  • May be up to 13 cm
Microscopic (histologic) description
  • Hypocellular, composed of bland cells, no mitotic activity, no lipoblasts, scant blood vessels; may have focal histiocytes
  • Slightly more cellular with collagenized capsule at periphery
  • May have areas of increased vascularity or be hypercellular (Am J Surg Pathol 1998;22:1222)
  • Slightly basophilic matrix with usually a few spindle cells at high power with oval nuclei
  • May have central mucinous cyst
  • At periphery, may infiltrate striated muscle and be associated with muscle atrophy
Microscopic (histologic) images

Contributed by Syed T. Hoda, M.D.

53 year old woman with subcutaneous thigh mass

Contributed by Mark R. Wick

Various images

Images hosted on other servers


Site unknown

Cytology description
  • Viscous, gelatinous quality when first applied to glass slide
  • Paucicellular, often finely granular myxoid stroma with few cells, usually macrophages and bland spindle cells (Am J Clin Pathol 2005;123:858)
Positive stains
Negative stains
Electron microscopy description
  • Fibroblast-like cell with prominent Golgi, endoplasmic reticulum, cytoplasmic filaments
Electron microscopy images

Images hosted on other servers:

Conjunctival myxoma

Molecular / cytogenetics description
Differential diagnosis
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