If the pathologic process involves only one TDLU or a few neighboring TDLUs, a unifocal lesion develops (Fig. 2.14).
Fig. 2.15
If the pathologic process simultaneously involves more than one distant TDLU leaving uninvolved TDLUs in between, the lesions are considered to be multiple (multi-focal) (Fig. 2.15).
Fig. 2.16
When there is simultaneous involvement of a large number of TDLUs, the lesion may exhibit a diffuse growth pattern (Fig. 2.16).
Thus, lesions in the breast may have one of the following three distributions: solitary (unifocal), multiple (multifocal) and diffuse.
If more than one TDLU is involved, all may exhibit the same pathologic process, but often different processes are present at the same time: in situ and invasive lesions coexist, different tumor types may be present, and the tumor grade may vary considerably within same specimen. The resulting complex histologic picture is an expression of intratumoral heterogeneity (Figs. 2.17 and 2.18). Intratumoral heterogeneity may develop even in a unifocal tumor when different tumor cell clones evolve during tumor progression and dedifferentiation.
Intratumoral heterogeneity may also make the measurement of the tumor size insufficient to represent the whole lesion. The entire area of the present invasive and in situ foci has to be assessed. This parameter is referred to as the extent of the disease.
Fig. 2.17
Fig. 2.18
The location of the lesions can be objectively determined by a combination of clinical, mammographic, and ultrasound parameters. To achieve uniform terminology, a horizontal plane and a vertical plane going through the nipple divide the breast into four quadrants: the upper lateral, upper medial, lower medial, and lower lateral. In addition, a fifth area of the central, retroareolar cylinder is defined (Fig. 2.19). By applying different orthogonal projections when imaging the breast, the radiologist can measure the distance between the lesion and the nipple. Since the location of the lesion within the breast cannot be determined solely from a histologic section, a system of marking the operative specimen is needed to provide orientation.
Fig. 2.19
Fig. 2.20
Mammography and ultrasound examinations provide a good overview of the entire breast. The size, extent (the involved area), distribution (unifocal, multifocal, or diffuse), and location of the lesions are usually well seen. Even when the lesions are not seen directly on the mammogram but are detected by indirect signs-such as microcalcifications-the size, extent, distribution, and location of the lesions can still be well marked. The size, extent, and distribution of the lesions are well seen on the specimen radiograph postoperatively (Figs. 2.20 and 2.21).
Histologic examination of the specimen is always necessary to further characterize the pathologic process after its size, extent, and distribution have already been indicated by the mammogram. Histologic examination should prove or rule out malignancy, delineate the in situ and the invasive components, grade and type the tumors, reveal intratumoral heterogeneity if present, and provide further morphologic-prognostic factors needed for therapy. Usually, and especially in cases of “indirect mammographic signs,” the more sensitive method of histology reveals more details than the mammogram itself.
Fig. 2.21
Conclusions
For a successful collaboration within the breast team, radiologists, surgeons, oncologists, and pathologists must each understand the terminology used by the other members of the team. Assessment of the size, distribution, extent, and location of the lesions preoperatively and postoperatively using the mammographic-pathologic correlative approach is a prerequisite for successful collaboration. These parameters are not only important diagnostic and prognostic features; they also represent the basis for proper planning of surgical interventions and oncologic therapy.
Chapter 3
Hyperplastic Changes with and without Atypia
The normal ducts and lobules in the breast exhibit a single layer each of epithelial and myoepithelial cells (Fig. 3.1).
Fig. 3.1
In epithelial hyperplasia, more than one layer of epithelial cells is present (Fig. 3.2).
Fig. 3.2
In myoepithelial hyperplasia, more than one layer of myoepithelial cells is seen (Fig. 3.3).
Fig. 3.3
Hyperplasia may be a focal or a diffuse phenomenon involving a portion of the terminal ductal-lobular unit (TDLU), the entire TDLU, or many TDLUs and ducts.
Epithelial hyperplasia may result in the formation of only two to three layers of epithelial cells (Fig. 3.4), but often many layers of epithelial cells are present and form glandlike spaces or small papilloma-like structures (“florid” epithelial hyperplasia, Fig. 3.5).
Fig. 3.4
Fig. 3.5
Neoplasia may also result in several layers of epithelial cells within the ducts and acini. Hyperplasia and neoplasia can be differentiated on the basis of their cellular and architectural characteristics.
Cellular Characteristics
Hyperplasia is a benign proliferation of several cell clones resulting in a polymorphous population of small cells (Fig. 3.6).
Fig. 3.6
Fig. 3.7
Low-grade malignant epithelial cells appear as a monoclonal, monomorphous population of small cells (Fig. 3.7). These cells also give rise to several layers of cells within the ducts and lobules,