Soft tissue

Uncertain differentiation

Intramuscular myxoma

Last author update: 1 November 2012
Last staff update: 12 February 2024 (update in progress)

Copyright: 2002-2024,, Inc.

PubMed Search: Myxoma soft tissue

Vijay Shankar, M.D.
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Cite this page: Shankar V. Intramuscular myxoma. website. Accessed April 15th, 2024.
Definition / general
  • 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. and Mark R. Wick, M.D.

53 year old woman with subcutaneous thigh mass

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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