Invasive breast carcinoma of no special type

Last revised by Mohammadtaghi Niknejad on 2 Jan 2024

Invasive breast carcinoma of no special type, previously known as invasive ductal carcinoma, not otherwise specified, is the most common type of breast cancer (70-80%) 5. It is an infiltrating and malignant proliferation of neoplastic cells in the breast tissues.

The 4th edition (2012) of the WHO classification of tumors of the breast changed the preferred terminology from "invasive ductal carcinoma (IDC), not otherwise specified (NOS)" to "invasive breast carcinoma (IBC) of no special type (NST)" 4. The rationale is that the term "ductal" relies on unproven histogenetic assumptions for this heterogeneous group of cancers. "Invasive ductal carcinoma" or "ductal NOS" remain acceptable and commonly used terms. 

The peak age of presentation is about 50-60 years. The Black population has a higher predisposition to grade 3 cancer and also a higher mortality rate.

Often presents as a large palpable, immobile mass.

The Nottingham combined histologic grade system, also called the modified Scarff-Bloom-Richardson grading system, is recommended by the College of American Pathologists. This grading system is based on the following criteria 6

  • tubule formation

    • 1 point: >75% of the tumor (majority of tumor)

    • 2 points: 10-75% of tubular formation

    • 3 points: <10% of tubular formation

  • nuclear pleomorphism

    • 1 point: nuclei with minimal or mild variation in size and shape

    • 2 points: nuclei with moderate variation in size and shape

    • 3 points: marked variation in size and shape

  • mitotic activity

    • 1 point: 0-5 per 10 high power fields (HPFs)

    • 2 points: 5-10 per 10 HPFs

    • 3 points: >10 per 10 HPFs

  • overall score

    • 3-5 points: grade 1 or well-differentiated tumor

    • 6-7 points: grade 2 or moderately-differentiated tumor

    • 8-9 points: grade 3 or poorly-differentiated tumor

  • irregular mass with or without calcifications

  • spiculated and hyperdense: 41% in grade 1 and 26% in grade 3

  • circumscribed: more commonly grade 3 (36%) 

  • microcalcifications: 34% in grade 1 and 37% in grade 3 5

    • amorphous: associated with low grade

    • pleomorphic: associated with high grade

  • ill-defined

  • hypoechoic mass

  • hyperechoic angular margins

  • posterior acoustic shadowing: 71% in grade 1

  • posterior enhancement: 45% in grade 3

  • ductal extension may be seen: represents extension of the mass into the surrounding parenchyma

  • branched or spiculated pattern

  • microcalcifications

Elastography depicts increased stiffness of the mass and the surrounding tissue. This feature correlates with the tumor grade 5.

  • T1

    • isointense to breast parenchyma

    • hypointense to fat

  • T1 C+ (Gd)

  • T2

    • iso to hypointense to parenchyma

    • hyperintense edematous zone

The Nottingham prognostic index (NPI) is used to determine the prognosis for invasive breast carcinoma after surgery 7.

NPI = (0.2 x S) + N + G

  • S: size of the lesion in centimeters

  • N: node status

    • 0 nodes = 1

    • 1-3 nodes = 2

    • >3 nodes = 3

  • G: grade of tumor (1 to 3)

Interpretation:

  • NPI ≤2.4 = excellent: 96% cancer-specific 10-year survival

  • NPI >2.4 and ≤3.4 = good: 93% cancer-specific 10-year survival

  • NPI >3.4 and ≤5.4 = moderate: 78% cancer-specific 10-year survival

  • NPI >5.4 = poor: 44% cancer-specific 10-year survival

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Cases and figures

  • Figure 1: histology
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  • Case 1
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  • Case 4
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  • Case 5: ultrasound
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  • Case 6: MRI
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  • Case 7: recurrence at mastectomy site
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  • Case 8: CT
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  • Case 9
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  • Case 10: incidental finding on CT
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  • Case 24
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  • Case 25a: mammography
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  • Case 25b: ultrasound
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  • Case 26
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  • Case 28: with cerebral and cerebellar metastases
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  • Case 29
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  • Case 30a: mammography
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  • Case 30b: ultrasound
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  • Case 30: elastography
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  • Case 31
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  • Case 36
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  • Case 37: male
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