Breast

Metaplastic carcinoma

Metaplastic


Editorial Board Member: Julie M. Jorns, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Huina Zhang, M.D., Ph.D.

Topic Completed: 8 April 2021

Minor changes: 24 May 2021

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PubMed Search: Metaplastic carcinoma [TI] breast "free full text" [SB]

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Huina Zhang, M.D., Ph.D.
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Cite this page: Zhang H. Metaplastic. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastmalignantmetaplastic.html. Accessed October 15th, 2021.
Definition / general
  • Heterogeneous group of invasive breast carcinomas characterized by differentiation of the neoplastic epithelium towards squamous cells or mesenchymal looking elements, including but not restricted to spindle, chondroid and osseous cells
Essential features
  • Invasive breast carcinoma with atypical squamous, spindle cell or mesenchymal / matrix producing differentiation
  • When lacking a ductal carcinoma in situ or conventual mammary carcinoma component, a panel of immunohistochemical stains (cytokeratins, including high molecular weight and p63) is needed to confirm the presence of epithelial differentiation
Terminology
  • Acceptable: metaplastic carcinoma, NOS
  • Not recommended: carcinosarcoma, sarcomatoid carcinoma, carcinoma with pseudosarcomatous metaplasia, carcinoma with pseudosarcomatous stroma
ICD coding
  • ICD-O: 8575/3 - metaplastic carcinoma, NOS
  • ICD-11: 2C6Y & XH0RD4 - metaplastic carcinoma of breast and metaplastic carcinoma, NOS
Epidemiology
  • Uncommon (0.2 - 1% of breast carcinomas)
  • Average 55 years
Sites
  • Any anatomical part of breast
Pathophysiology
Clinical features
Diagnosis
  • By histopathological examination
Radiology description
Radiology images

Images hosted on other servers:
Mammography shows a spiculated mass with associated nipple retraction and skin thickening

Spiculated mass

Prognostic factors
Case reports
Treatment
  • Mastectomy or local excision, with or without radiation and chemotherapy
  • Lower response rates to conventional chemotherapy (Breast J 2019;25:418)
Clinical images

Images hosted on other servers:
Right breast mass

Right breast mass

Gross description
  • Often firm, well circumscribed and solid
  • Pearly, white to grayish and glistening cut surface in areas of squamous and chondroid differentiation
  • Mean 3.9 cm, ranging from 2 cm to > 10 cm
Gross images

AFIP images

Bisected squamous tumor

Carcinoma with osteoclast-like giant cells



Images hosted on other servers:
Well circumscribed<br>mass with<br>central bleeding

Well circumscribed
mass with
central bleeding

Causing skin ulceration

Causing skin ulceration

Sharply circumscribed tumor

Sharply circumscribed tumor

Microscopic (histologic) description
  • Morphologically heterogenous
  • Can be epithelial only carcinomas, pure (monophasic) sarcomatoid carcinomas and biphasic epithelial and sarcomatoid carcinomas
  • Epithelial only carcinomas include low grade adenosquamous carcinoma, high grade adenosquamous carcinoma and squamous cell carcinoma
  • Pure (monophasic) sarcomatoid carcinomas include fibromatosis-like metaplastic carcinoma and spindle cell carcinoma
  • Heterologous mesenchymal components include chondroid, osseous, rhabdomyosarcomatous, angiosarcomatous, liposarcomatous and neuroglial differentiation or in combination
  • Mesenchymal component can show a wide spectrum of atypia, ranging from minimal atypia to frankly malignant
  • May need to look carefully, extensive sampling or performing immunohistochemistry (a combination of several stains) for identification of epithelial component
Microscopic (histologic) images

Contributed by Huina Zhang, M.D., Ph.D. and Julie M. Jorns, M.D.
Spindle cell carcinoma Spindle cell carcinoma Spindle cell carcinoma Spindle cell carcinoma Spindle cell carcinoma Spindle cell carcinoma

Spindle cell carcinoma


Metaplastic carcinoma with squamous differentiation Metaplastic carcinoma with squamous differentiation

Metaplastic carcinoma with squamous differentiation

Matrix producing metaplastic carcinoma

Matrix producing metaplastic carcinoma

Squamous type Squamous type Squamous type

Squamous type


Spindle cell type Spindle cell type Spindle cell type

Spindle cell type

Osseous differentiation

Osseous differentiation

Spindle cell type Spindle cell type

Spindle cell type


Chondromyxoid matrix producing

Chondromyxoid matrix producing



Contributed by Indu Agarwal M.D. and Semir Vranić, M.D., Ph.D.
Chondroid differentiation Chondroid differentiation

Chondroid differentiation

Squamous component

EGFR expression

Virtual slides

Images hosted on other servers:
Fibromatosis-like metaplastic carcinoma

Fibromatosis-like metaplastic carcinoma

Cytology description
Positive stains
Negative stains
Molecular / cytogenetics description
Videos

Metaplastic carcinoma by
Dr. Alexander Damron

Sample pathology report
  • Breast, left, 3:00 (mass), ultrasound guided core needle biopsy:
    • Malignant spindle cell lesion, consistent with spindle cell carcinoma (see comment)
    • Comment: H&E sections show a high grade spindle cell lesion with pleomorphic nuclei, irregular nuclear borders and occasional mitotic figures, including atypical mitosis. There is no leaf-like growth pattern. Immunohistochemical staining shows that the neoplastic cells are positive for pancytokeratin, p63, CK5 and AE1 / AE3 and are negative for CD34. The morphology and immunoprofile of this malignant spindle cell lesion are consistent with a spindle cell (metaplastic) carcinoma.
Differential diagnosis
  • Phyllodes tumor:
    • Leaf-like growth pattern
    • Benign epithelial elements
    • HMWCK, CK5/6 negative
  • Primary breast sarcoma:
  • Metastatic sarcoma:
  • Adenomyoepithelioma:
    • Bland epithelial and stromal component
    • Stromal only with myoepithelial differentiation
    • Lack of squamous differentiation
  • Myoepithelial carcinoma:
    • Entirely or almost entirely malignant spindle cells with myoepithelial differentiation
    • No squamous component or other mesenchymal differentiation
  • Pleomorphic adenoma:
    • Usually retroareolar region
    • Well organized biphasic pattern with inner layer of regular epithelial cells
    • Thin, continuous outer layer of myoepithelial cells
    • No cytologic atypia, atypical mitosis or necrosis
  • See others in variants sections
Board review style question #1


A 55 year old woman without significant medical history was found to have a 2.5 cm mass on mammogram and a biopsy was performed. Histology and immunohistochemical stain for p63 were shown (see images above). What is the likely diagnosis?

  1. Malignant phyllodes tumor
  2. Metaplastic carcinoma
  3. Metastatic sarcoma
  4. Primary breast sarcoma
Board review style answer #1
B. Metaplastic carcinoma

H&E section shows a high grade spindle cell lesion with pleomorphic nuclei, irregular nuclear borders and occasional mitotic figures, including atypical mitosis. Based on the morphology, all the listed choices should be considered. Performing a panel of immunohistochemical stains including high molecular weight cytokeratin and p63 is very important and helpful. In this case, the positivity for p63 (as well as other cytokeratins, not shown here) supports the diagnosis of spindle cell carcinoma and makes other choices less likely. It needs to be noted that cytokeratins and p63 are often focal and patchy, therefore a panel of immunostains is usually needed.

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Reference: Metaplastic carcinoma
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