Invasive Tumor Size

In the TNM system for staging breast cancer, the T is based on the size of the largest invasive component. Although measurement of the tumor in three dimensions is helpful for monitoring change for women undergoing neoadjuvant chemotherapy, only the longest dimension is used in staging. When there is more than one invasive focus, only the largest is considered in staging. Tumors are classified as Tis (in situ), T1 (≤20 mm), T2 (21-50 mm), or T3 (>50 mm). T1mi refers to microscopic invasion of less than 1 mm.

Tumor size is measured at histologic examination. However, there are times when the size on imaging may be used, such as when the tumor is very small and mostly removed at core biopsy or in the setting of neoadjuvant chemotherapy. For invasive carcinoma, US size that includes the echogenic rim correlates best with histologic size ( Fig. 17-1 ). Measurements of invasive carcinoma on MRI correlate best with size at histologic evaluation. This is especially true for invasive lobular carcinoma (ILC) ( Fig. 17-2 ).

Ultrasound Measurement of Tumor Size.

The longest dimension that includes the echogenic margin ( green line ) correlates better with the size at histologic examination than does just the hypoechoic mass ( red line ). The measurement does not need to be parallel to the face of the transducer.

Size of ILC on MRI.

On mammography and US, this palpable ILC measures 2.4 cm. On MRI, however, the mass was considerably larger, measuring 4.5 cm. At histologic examination, the mass measured 5 cm. The enhancement in the left breast is due to a contralateral MRI-detected invasive ductal carcinoma (IDC).

Associated Ductal Carcinoma in Situ

Now that you have identified a mass that is suspicious for invasive carcinoma, let’s look to see whether there is also associated DCIS. Mammography is a good place to start. Breast cancer typically affects a single ductal system. If we recall the tree branch analogy from Chapter 5 , Breast Anatomy and Physiology, we will want to focus our attention on the ductal system where the mass is located. We will especially want to look for calcifications between the mass and the nipple, as well as between the mass and the chest wall ( Fig. 17-3 ). Recall that one ductal system can extend over a wide area in the breast, so even calcifications that are not immediately adjacent to an invasive carcinoma may represent DCIS.

IDC with Associated DCIS.

A 48-year-old woman with a screening detected mass in her left breast ( arrows ). On a magnification view, round and punctuate calcifications in a segmental distribution are seen extending between the mass and the nipple ( blue arrows ). Mild ductal dilatation is also seen. Although the morphologic appearance of the calcifications is of low suspicion, their segmental distribution is suspicious especially because they lie in the same ductal system as the mass. Biopsy of the mass revealed IDC with DCIS; the retroareolar calcifications represented additional DCIS.

MRI can also be very helpful in assessing the extent of DCIS associated with a primary invasive cancer. The associated DCIS will usually present as nonmass enhancement in the same ductal distribution ( Fig. 17-4 ).

MRI-Detected DCIS in Patient with IDC.

This patient presented with a palpable lump in the left breast that corresponded to a suspicious mass on US. Her mammogram was negative. Biopsy showed IDC. MRI performed to evaluate extent of disease shows the mass ( blue arrow ) with associated segmental nonmass enhancement ( yellow arrows ) that represented extensive DCIS.

Extent of Ductal Carcinoma in Situ

The extent of calcifications on mammography typically correlates well with DCIS that is high grade, but low-grade DCIS often has more extensive noncalcified disease.

When the primary lesion presents as suspicious calcifications, other calcifications that are morphologically similar are likely to represent additional disease ( Fig. 17-5 ). Calcifications of differing morphologic appearance may also need to undergo sampling if they are also suspicious based on morphologic appearance, distribution, or change over time ( Fig. 17-6 ).

Suspicious Calcifications with Similar Morphologic Appearance.

Biopsy of the most suspicious area ( yellow arrow ) showed DCIS. If the patient desires breast-conserving therapy, then biopsy of the posterior and anterior groups ( green arrows ) can help determine extent of disease.

Suspicious Calcifications of Differing Morphologic Appearance.

Green marks denote two areas of calcifications on the screening craniocaudal (CC) view. Calcifications in the lateral breast are fine pleomorphic, whereas those in the medial breast are coarse heterogeneous. Biopsy of either cluster could be benign or malignant and acted upon independently. Therefore, biopsy of both should be performed. Histologic diagnoses: DCIS, low-grade lateral breast; DCIS, high-grade medial breast.

This does not mean that you must biopsy every cluster of calcifications in the breast! If the calcifications are of similar morphologic appearance, do a biopsy of the most suspicious finding first (see Fig. 17-5 ). If the biopsy shows cancer and the patient desires mastectomy, doing a second biopsy will not alter her management. On the other hand, if the patient desires breast-conserving therapy, an additional biopsy may be needed to establish the extent of disease. In our practice, a second biopsy of the ipsilateral breast is not typically performed until the results of the biopsy showing cancer have been discussed with the patient and she has seen a breast surgeon to discuss surgical options.

DCIS with Associated Invasive Disease

When the primary lesion is malignant-appearing calcifications and you are suspecting DCIS, finding an invasive component changes the stage from 0 to I. Providing the patient and surgeon with the higher stage of disease is helpful because the patient may then need a sentinel lymph node biopsy. An invasive component may be suspected when there is density that looks like a puff of smoke overlying the calcifications ( Fig. 17-7 ). US is useful in evaluating these patients. An invasive focus will appear as a hypoechoic mass, whereas DCIS will appear as an expanded duct with calcifications (see Fig. 17-7 ). US is also useful when malignant calcifications are present in dense breast tissue that could be masking an invasive carcinoma ( Fig. 17-8 ). US does not need to be performed for every patient with suspicious or malignant calcifications. If an associated mass is not definitely identified by US, stereotactic biopsy is preferred over ultrasound-guided biopsy because it is less likely to show only atypical ductal hyperplasia because of undersampling.

Suspicious Calcifications with Associated Density.

CC magnification view from this screening recall shows two adjacent suspicious groups of calcifications with similar morphologic appearances in the same ductal distribution. The posterior group ( yellow arrow ) has an associated density that corresponds to a hypoechoic mass ( yellow arrows ) with calcifications ( green arrow ) on US. Histologic diagnosis: multifocal DCIS with IDC at the posterior site.

Malignant Calcifications with Suspicious Mass on US.

CC magnification view shows malignant coarse heterogeneous and fine pleomorphic calcifications in a segmental distribution that are highly suspicious for DCIS (BI-RADS 5). US is useful to identify an invasive component in the setting of malignant calcifications in dense breast tissue. US shows a hypoechoic solid mass ( arrow ) with calcifications. Ultrasound-guided core needle biopsy showed IDC, grade III. You may have noticed a small round mass at the top of the CC magnification view. This was a metastatic intramammary lymph node. These are generally managed as though they were another focus of invasive cancer.

Multifocal Invasive Carcinoma

Small masses or asymmetries in the same ductal distribution as the primary lesion should be viewed with suspicion. When additional invasive disease is separated by less than 4 cm, the cancer is considered to be multifocal ( Fig. 17-9 ). Although different criteria are used to determine whether carcinomas should be classified as multifocal (vs. multi centric ), the less-than-4-cm measurement correlates well with a lower chance of local recurrence when compared with more extensive lesions ( Box 17-1 ).

Multifocal Invasive Carcinoma.

A 51-year-old woman presents with a palpable left breast mass marked with a BB . There is an irregular spiculated mass corresponding to the palpable lesion. On US a second, smaller mass ( arrow ) is seen 2 to 3 cm from the palpable mass. This appears as an asymmetry ( arrow ) on the mediolateral oblique (MLO) spot compression view. The palpable mass was IDC and the nonpalpable lesion IDC with DCIS.

US is very useful to identify multifocal invasive carcinoma. Remember our tree? With the transducer oriented in the radial plane, sweep the area between the cancer and the nipple and then the cancer and the periphery of the breast to identify additional lesions within the branches of the involved ductal system (see Fig. 17-9 ).

MRI is very sensitive for detecting additional invasive breast carcinoma ( Fig. 17-10 ).

DCIS with Multifocal Invasive Carcinoma on MRI.

This patient had a stereotactic core biopsy for a group of calcifications in the right breast showing DCIS. Axial T1 postcontrast image, axial maximum intensity projection (MIP), and sagittal right breast MIP show nonmass enhancement ( yellow arrows ) with several enhancing masses ( blue arrows ) in the same ductal distribution. Histologic examination showed DCIS with multifocal IDC.

Multicentric Carcinoma

Additional ipsilateral cancer that is more than 4 cm from the primary lesion is considered multicentric. This may or may not be identified in a different quadrant. Satisfaction of search is difficult to overcome. Ignore that really concerning finding and really look at the rest of that breast (see Fig. 17-6 ). Diagnosis of multicentric carcinoma is generally a contraindication for breast-conserving therapy, though it is not an absolute contraindication.

Skin or Chest Wall Involvement

Remember the T classification earlier? We only gave you T0 to T3, but there is also a T4 category that is defined by involvement of the skin or chest wall with tumor. Skin involvement is defined as skin nodules or ulceration ( Fig. 17-11 ), not just dermal invasion. Chest wall involvement is invasion into the intercostal muscles or ribs. Invasion of the pectoral muscles may influence surgical or medical management, but is not considered chest wall invasion. Inflammatory cancer is also considered T4.

Skin Involvement, Stage IIIB.

RMLO shows an irregular mass in the low axilla ( arrows ). US shows a heterogeneous mass ( yellow arrows ) involving the dermis ( green arrows ). MRI shows an enhancing mass in the tail of the breast with enhancement of the skin ( arrow ). On clinical examination, the patient has a skin nodule. Histologic diagnosis: ILC.

If you are a “lumper,” then skip this paragraph. If you are a “splitter,” then you’ll want to know the T4 subcategories. T4a is invasion of the chest wall. T4b is tumor associated with skin ulceration, ipsilateral skin nodules, or skin edema that does not meet criteria for inflammatory breast carcinoma. T4c is findings of both T4a and T4b. T4d is inflammatory carcinoma.

Inflammatory carcinoma is most commonly associated with invasive ductal carcinoma—not otherwise specified (IDC-NOS). It is not associated with DCIS alone. The diagnosis of inflammatory carcinoma may be clinical (red, swollen breast in a patient with invasive carcinoma) or histologic (punch biopsy of the skin showing invasion of the dermal lymphatics).

Paget Disease Is Not T4

Although Paget disease is tumor ulceration of the skin of the nipple, it is not considered T4 disease. If Paget disease is only associated with DCIS, then it is stage Tis. If a woman with Paget disease has an associated invasive carcinoma, then the T status is based on the size of the invasive carcinoma.

Contralateral Breast Cancer

The incidence of synchronous contralateral breast cancer is 0.1% to 2% by mammography and 3% to 5% by MRI ( Fig. 17-12 ). Ignore the ipsilateral breast for a moment and really focus on the other breast. Bilateral breast cancer diagnosed at the same time is considered synchronous, whereas diagnosis that occurs at least 6 months apart is considered metachronous.

Contralateral Synchronous Breast Cancer in Two Patients.

This may be diagnosed on mammography ( A ) or MRI ( B ). A, This patient had right calcifications that were DCIS and a left mass that was a tubular carcinoma. B, MRI on a different patient who had a known right ILC with a left IDC detected on MRI.