Breast

Metaplastic carcinoma

Fibromatosis-like


Editorial Board Member: Julie M. Jorns, M.D.
Deputy Editor-in-Chief: Gary Tozbikian, M.D.
Kristen E. Muller, D.O.

Last author update: 28 March 2022
Last staff update: 28 March 2022

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PubMed Search: Fibromatosis-like metaplastic carcinoma

Kristen E. Muller, D.O.
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Cite this page: Muller KE. Fibromatosis-like. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastmalignantmetaplasticfibro.html. Accessed July 5th, 2022.
Definition / general
  • Variant of metaplastic carcinoma with low grade, bland spindle cells histologically resembling fibromatosis
  • May arise de novo or in association with papillary or sclerosing lesions
  • High propensity for local recurrence but lymph node and distant metastases are rare
  • May represent a distinct subtype as these tumors do not share similar genomic alterations with other types of metaplastic carcinomas
Essential features
  • Variant of metaplastic carcinoma composed of cytologically bland spindle cells resembling fibromatosis within abundant stromal collagen
  • Immunohistochemical stains needed to establish epithelial differentiation (cytokeratins, p63) since in situ and conventional type invasive breast carcinoma are typically absent
Terminology
  • Low grade fibromatosis-like metaplastic carcinoma
  • Fibromatosis-like spindle cell metaplastic carcinoma
ICD coding
  • ICD-O: 8575/3 - metaplastic carcinoma, NOS
  • ICD-11: 2C6Y & XH0RD4 - metaplastic carcinoma of breast & metaplastic carcinoma, NOS
Epidemiology
Sites
  • Breast, unilateral
Pathophysiology
  • Unknown; may arise in association with papillary or sclerosing lesions
Etiology
  • Unknown
Clinical features
Diagnosis
  • Core needle biopsy or surgical excision
Radiology description
  • Variable appearance: round, oval, lobular or irregularly shaped; densely solid, heterogeneous or cystic parenchyma; well circumscribed or irregular / spiculated shaped (Arch Pathol Lab Med 2015;139:552)
  • Calcifications uncommon
Radiology images

Images hosted on other servers:

Mammogram, microlobulated high density mass

Ultrasound, hypoechoic mass

MRI, irregular mass with heterogeneous enhancement

Prognostic factors
Case reports
Treatment
Gross description
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Kristen E. Muller, D.O. and Julie M. Jorns, M.D.
Fibromatosis-like metaplastic carcinoma

Fibromatosis-like metaplastic carcinoma

Squamous and glandular elements

Squamous and glandular elements

Fascicular arrangement

Fascicular arrangement

Bland spindle cells

Bland spindle cells

Round cells with nucleoli

Round cells with nucleoli

Focal squamous and glandular elements

Focal squamous and glandular elements


Infiltrative border Infiltrative border

Infiltrative border

p63

p63

CK MNF 116

CK MNF 116

Virtual slides

Images hosted on other servers:

Breast fibromatosis-like metaplastic carcinoma

Cytology description
  • Low cellularity smear with clusters of round to oval and spindle shape cells with low grade, bland nuclear features (Acta Cytol 2010;54:712)
Positive stains
Electron microscopy description
  • Tumor cells show fibroblastic, myoepithelial and epithelial features with peripheral villous processes with a focal basal lamina and intercellular junctions (World J Surg Oncol 2007;5:24)
Electron microscopy images

Images hosted on other servers:
Fibroblastic, myoepithelial and epithelial features

Fibroblastic, myoepithelial and epithelial features

Molecular / cytogenetics description
Sample pathology report
  • Breast, right, partial mastectomy:
    • Fibromatosis-like spindle cell metaplastic carcinoma (see comment and synoptic report for additional details and staging)
    • Comment: H&E sections show an infiltrative spindle cell tumor arranged in long sweeping fascicles. The lesional cells lack significant nuclear atypia and mitotic activity is scarce. Conventional in situ (DCIS) and invasive carcinoma are not identified. Immunohistochemical staining shows that the tumor cells are positive for multiple cytokeratins (CK5, CK MNF 116, CK AE1 / AE3) and p63. The morphology and immunoprofile are consistent with fibromatosis-like metaplastic carcinoma.
Differential diagnosis
Board review style question #1

The lesion depicted in the image was taken from a 67 year old woman with a 2 cm mass. Which immunohistochemical panel supports a diagnosis of fibromatosis-like metaplastic carcinoma?

  1. ER positive, CD34 negative, beta catenin cytoplasmic expression
  2. ER positive, CD34 negative, beta catenin nuclear expression
  3. ER negative, CK AE1 / AE3 negative, beta catenin cytoplasmic expression
  4. ER negative, CK AE1 / AE3 positive, beta catenin cytoplasmic expression
Board review style answer #1
D. ER negative, CK AE1 / AE3 positive, beta catenin cytoplasmic expression. Fibromatosis-like metaplastic carcinoma shows the following immunoprofile: cytokeratin positive (typically high molecular weight and broad spectrum keratins), p63 positive, ER, PR and HER2 negative and are CD34 negative. A distinguishing factor in differentiating this lesion with desmoid type fibromatosis is the lack of nuclear beta catenin expression that is characteristic of fibromatosis.

Comment Here

Reference: Fibromatosis-like metaplastic carcinoma
Board review style question #2

The lesion depicted in the image was taken from a 72 year old woman with a 3 cm mass. The lesional cells showed scattered expression of CK5/6 and p63. Focal squamous differentiation was seen, which comprised approximately 2% of the tumor. Which statement is true regarding this lesion?

  1. These tumors typically lack cytologic atypia and conspicuous mitoses
  2. This variant is an unfavorable pattern of metaplastic breast carcinoma with frequent lymph node metastases
  3. This variant is commonly associated with conventional invasive ductal carcinoma or ductal carcinoma in situ
  4. This variant shares similar molecular alterations with other variants of metaplastic breast carcinoma
Board review style answer #2
A. These tumors typically lack cytologic atypia and conspicuous mitoses. The photo and vignette describe a fibromatosis-like metaplastic breast carcinoma. These tumors can histologically mimic desmoid type fibromatosis and are composed of bland spindle cells arranged in long sweeping fascicles with infrequent mitotic activity. Focal glandular and squamous elements can be present; however, conventional invasive carcinoma and ductal carcinoma in situ are rarely present. Compared to other variants of metaplastic breast carcinomas, fibromatosis-like metaplastic carcinoma portends a more favorable prognosis with infrequent lymph node and distant metastases. These tumors show low genomic instability and do not share copy number alterations with other metaplastic carcinoma types.

Comment Here

Reference: Fibromatosis-like metaplastic carcinoma
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