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Breast-malignant, males, children

Low grade myofibroblastic sarcoma

 

Author: Nat Pernick, M.D, PathologyOutlines.com, Inc.

Reviewer: Daniel Visscher, M.D., University of Michigan Hospitals, February 2009 (see Reviewers page)

Revised: 1 October 2009

Last major update: October 2009

Copyright: (c) 2002-2009, PathologyOutlines.com, Inc.

 

Definition

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● Rare malignant tumor of myofibroblasts

 

Terminology

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● Also called myofibrosarcoma

● Not part of WHO breast classification

 

Clinical

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● Commonly recurs, only rarely metastasizes

 

Case reports

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● 55 year old woman with death due to metastatic tumor (AJSP 1997;21:489)

 

Gross

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● Firm, pale, fibrous cut surface, ill defined margins

 

Microscopic description

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● Fascicles of spindle cells surrounded by dense collagen

● Cells have ill defined, pale, eosinophilic cytoplasm, fusiform and pleomorphic nuclei, numerous mitotic figures

● Also some giant cells

● Margins are infiltrative, often grossly (Pathol Res Pract 1999;195:1)

 

Micro images

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Fig 1A: fascicular growth

Fig 1B: alpha smooth muscle actin+, vimentin+ (insert)

Fig 1C: fibronectin+ matrix

Fig 1D: type IV collagen negative

 

Positive stains

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● At least one myogenic marker (desmin, alpha smooth muscle actin, muscle specific actin or calponin)

 

Negative stains

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● S100, EMA, h-caldesmon, ALK

 

Electron microscopy

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● Features of myofibroblasts: discontinuous basal lamina, abundant rough endoplasmic reticulum, intermediate filaments and myofilaments; indented and clefted nuclei

 

EM images

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Fig 2A: arrows point to thin filaments at the cell surface suggestive of fibronexus junctions

Fig 2B: arrows point to fibronectin fibrils extending into the extracellular matrix

 

Molecular

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● 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)

 

Differential diagnosis

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● Leiomyosarcoma - alternating fascicular pattern, usually high grade

● Fibromatosis / myofibromatosis

● Fibrosarcoma

● Inflammatory myofibroblastic tumor - more heterogeneous, less cellular, less hyperchromasia, less infiltrative, ALK+ (Hum Pathol 2008;39:846)

● Myofibroblastoma - may be some pleomorphism, but low mitotic activity

● Nodular fasciitis - not infiltrative, not deep, lacks chromosomal anomalies

● Solitary fibrous tumor

 

Additional references

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AJSP 1998;22:1228

 

End of Breast Malignant, Males, Children > Low grade myofibroblastic sarcoma

 

 

 

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