Low grade myofibroblastic sarcoma

Last author update: 1 September 2016
Last staff update: 8 March 2021

Copyright: 2002-2022,, Inc.

PubMed Search: Low grade myofibroblastic sarcoma

Emily S. Reisenbichler, M.D.
Page views in 2021: 1,581
Page views in 2022 to date: 937
Cite this page: Reisenbichler ES. Low grade myofibroblastic sarcoma. website. Accessed August 17th, 2022.
Definition / general
  • Spindle cell sarcoma with myofibroblastic differentiation
  • Also called myofibrosarcoma
Essential features
  • Uncommon tumor overall, occurring predominantly in the head and neck or extremities with only rare reports within the breast
  • At least moderate cytologic atypia must be seen focally
  • Not part of WHO breast classification
Prognostic factors
  • Frequently recurs, particularly when incompletely excised
  • Low rates of metastasis but lung is most common site when it occurs (Am J Surg Pathol 2001;25:219)
Case reports
Gross description
  • Well circumscribed tumor with firm, pale cut surface, despite infiltrative microscopic growth
Microscopic (histologic) description
  • Spindle cells in a fascicular or storiform growth pattern
  • Variable stromal collagen
  • Cells demonstrate pale eosinophilic cytoplasm and the nuclei must show at least moderate atypia focally and hyperchromasia
  • Diffusely infiltrative borders
Microscopic (histologic) images

Contributed by Dr. Mark R. Wick

Images hosted on other servers:

Low grade myofibroblastic sarcoma arising in fibroadenoma

Positive stains
Negative stains
Electron microscopy description
  • Prominent rough endoplasmic reticulum, peripheral myofilaments and the fibronectin fibrils of the fibronexus junctions (J Clin Pathol 2009;62:236)
Molecular / cytogenetics description
  • Gains at 1p11 → p36.3 (66%), 12p12.2 → p13.2 (45%), 5p13.2 → p15.3 (31%), +22 (28%), loss at 15q25 → q26.2 (24%) (Am J Clin Pathol 2009;131:701)
  • Complex DNA copy number changes
  • Higher average number of chromosomal aberrations than seen in nodular fasciitis
Differential diagnosis
  • Desmoid fibromatosis: long sweeping fascicles with stromal collagen deposition; lacks cytologic atypia
  • Inflammatory myofibroblastic tumor: variably cellular fascicles; background lymphoplasmacytic infiltrate; lacks cytologic atypia; ALK positive in ~ 50%
  • Leiomyosarcoma: shorter fascicles, lacks stromal collagen, h-caldesmon positive
  • Myofibroblastoma: short, intersecting fascicles with stromal collagen deposition; lower mitotic activity; desmin and CD34 positive
  • Myofibromatosis: lacks cytologic atypia; biphasic fascicular and pericytoma-like areas; nodular growth, protruding into vascular spaces; lacks cytologic atypia
  • Nodular fasciitis: lacks fascicular growth pattern and cytologic atypia; border is typically not infiltrative; usually small (< 3 cm)
  • Solitary fibrous tumor: spindle cells lacking a fascicular architecture (i.e.“patternless pattern”); hemangiopericytoma-like vessels
  • Spindle cell (metaplastic) carcinoma: at least focal keratin positivity
  • Spindle cell rhabdomyosarcoma: fascicular growth; typically more cellular; positive myogenin and myoD1
Back to top
Image 01 Image 02