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Breast malignant, males, children

Male tumors

Myofibroblastoma of breast


Reviewer: Monika Roychowdhury, M.D. (see Reviewers page)
Revised: 8 November 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

Definition
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● Rare benign spindle cell tumor of mammary stroma composed of myofibroblasts
● First described in 1987 (Am J Surg Pathol 1987;11:493)

Terminology
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● Also called benign stromal spindle cell tumor with predominant myofibroblastic differentiation

Epidemiology
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● Although initially considered male predominant, now equal gender frequency (older men and post-menopausal women, Mod Pathol 1996;9:786)
● Incidence appears to be increasing, but probably an artifact of mammographic screening (Arch Pathol Lab Med 2008;132:1813)

Etiology
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● May derive from CD34+ vimentin+ fibroblasts of mammary stroma capable of multidirectional differentiation (Histopathology 2003;42:233)
● Probably related to spindle cell lipoma and solitary fibrous tumor (Virchows Arch 2002;440:249, Am J Surg Pathol 2001;25:1022, Breast J 2008;14:287)

Clinical features
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● Solitary, slow growing nodule
● Benign behavior

Case reports
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● 10 month old boy (Fetal Pediatr Pathol 2012;31:164)
● 25 year old man with bilateral gynecomastia (Int J Surg Pathol 2001;9:331)
● 40 year old woman (Indian J Pathol Microbiol 2008;51:395)
● 59 year old woman (University of Pittsburgh, Case #249)
● 65 year old man with 15 cm rapidly growing tumor (J Med Case Rep 2008;2:157)
● 72 year old man (Arch Pathol Lab Med 2003;127:e415)
● 73 year old man with cellular tumor (Am J Mens Health 2012;6:344)
● 83 year old man with 10 cm tumor (Am J Surg Pathol 1994;18:1170)
● Post-radiation tumor (Breast J 1999;5:136)

Treatment
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● Excision is curative

Clinical images
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15 cm tumor

Gross description
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● Well-circumscribed nodule or multilobar mass
● Bulging, gray-pink and 1-4 cm
● Resembles fibroadenoma

Gross images
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Firm, circumscribed, tan-gray lobulated nodule

Micro description
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● Well-circumscribed
● Uniform, bland spindle cells haphazardly arranged in fascicles with pushing borders, separated by broad bands of hyalinized collagen (Stanford University)
● Spindle cells have abundant eosinophilic cytoplasm, round / oval nucleus with 1-2 small nucleoli
● May have mild nuclear pleomorphism
● Prominent mast cells
● Variants include cellular, collagenized, epithelioid (Am J Surg Pathol 2009;33:1085), fatty (J Clin Pathol 2001;54:568) and infiltrative (no atypia or mitotic activity)
● May have histiocytoid cells, prominent vessels, focal cartilaginous differentiation (Virchows Arch 1999;434:547), smooth muscle and multinucleated floret-like giant cells
● No / rare mitotic activity
● Usually no entrapment of ducts or lobules
● Usually no necrosis

Micro images
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Epithelioid type

   
Well circumscribed              Spindle cells and hyalinized collagen


Fascicles of spindle cells separated by dense collagen

       
Classic type       Cellular variant     Other variants


Predominantly fatty variant


CD34+


H&E, CD34, SMA



Fig 1: sharply circumscribed tumor with fibrous pseudocapsule
fig 2: bland spindle cells in collagenous or myxoid stroma
fig 3A: CD34+; fig 3B: bcl2+; fig 4: desmin+ (focal)

Cytology description
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● May appear malignant
● Cohesive and single spindle cells without atypia
● Scant cytoplasm and oval nuclei with fine granular chromatin, occasional nuclear grooves and small nucleoli (Diagn Cytopathol 2004;30:406)
● Tumor cells may be intimately associated with extracellular matrix material
● Also mast cells, hyaline bands between tumor cells (Diagn Cytopathol 2002;26:290)
● May have features of solitary fibrous tumor or pleomorphic lipoma (Pathol Res Pract 1999;195:257)

Cytology images
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Fig 2: loose groups of cells with abundant eosinophilic granular cytoplasm and bland nuclei

Positive stains
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● ER, PR (Histopathology 2000;36:515), vimentin and CD34 (often)
● bcl2
● Variable desmin, caldesmon and androgen receptors (Hum Pathol 1998;29:347)

Negative stains
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● S100, cytokeratin
● Ki-67 (or low)

Molecular description
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● 13q-, 16q- (similar to spindle cell lipoma, J Pathol 2000;191:282)

Electron microscopy description
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● Features of smooth muscle and myofibroblasts: rough endoplasmic reticulum, bundles of myofilaments with focal densities, intermediate filaments and attachment plaques (Ultrastruct Pathol 1999;23:249, Pathol Res Pract 1999;195:1)

Differential diagnosis
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Fibromatosis: not circumscribed, more diffuse fibrosis and no thick bands of collagen
Nodular fasciitis: more infiltrative, mucoid stroma
Low grade myofibroblastic sarcoma: marked cellular pleomorphism, infiltrating margins and high mitotic rate
Myoepithelioma: S100+, keratin+

End of Breast malignant, males, children > Male tumors > Myofibroblastoma of breast


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