of the lobules are seen, not the histologic details. A radiologic nodular density may represent a spectrum of histologic changes within the TDLU (Figs. 1.42-1.44). The radiologic linear densities correspond to ducts, fibrous strands, and vessels (Fig. 1.45).
Fig. 1.44
Fig. 1.45
Despite the variability of the histologic picture, the mammographic patterns of the normal breast can be properly classified in only five categories as described by Tabár, Gram and Tot. The basic factor determining the mammographic pattern of the normal breast is the interrelation between the radiopaque fibrous tissue and the radiolucent fatty tissue in the interlobular stroma.
Mammographic pattern I is characterized by Cooper ligaments as well as a harmonic distribution of fatty and fibrous tissue (Figs. 1.46-1.48).
Fig. 1.46
Fig. 1.47
Fig. 1.48
Fig. 1.49
Mammographic pattern II represents breast tissue replaced by fatty tissue with only a few remaining TDLUs (Figs. 1.49 and 1.50).
Fig. 1.50
Pattern I develops over time into pattern II through fatty involution. Hormone replacement therapy may convert pattern II back to pattern I. The mammographic pattern of the normal breast is often characterized as intermediate between patterns I and II or as “involuting pattern I.”
Pattern IN is characterized by a relatively fibrotic area behind the nipple when the remainder of the breast has been replaced by adipose tissue (Fig. 1.51). The same pattern can be produced by advanced ductectasia.
Fig. 1.51
Fig. 1.52
Fig. 1.53
Fig. 1.54
Fig. 1.55
Pattern IV is dominated by somewhat enlarged nodular densities, approximately 3 to 5 mm in size (Figs. 1.52 and 1.53). These densities usually represent different ANDIs, but focal involution of the interlobular stroma with small islands of remaining fibrous tissue may present the same picture (see Fig. 1.43).
Pattern V shows a radiopaque density over the entire gland corresponding to a more collagenous interlobular stroma (Figs. 1.54 and 1.55). Radiologic details (nodular or linear densities) are poorly seen; active and/or atrophic parenchyma may be hidden within this density. Patterns IV and V are stable and do not change during the woman's lifetime.
Conclusions
Comprehensive knowledge of the variations of normal breast morphology enables the pathologist to avoid over-diagnosing normal variations as pathologic processes.
Clinical and radiologic diagnoses assist the pathologist in the delineation of normal tissue from fibrocystic change.
The particular mammographic pattern of breast tissue is an important aid for the pathologist. Detection of pathologic changes in breasts with patterns I, II, and III is relatively easy, but a more detailed histologic analysis of macroscopically and radiologically normal breast tissue is necessary in patients with patterns IV and V.
References
1 Vogel PM, et al. The correlation of histological changes in the human breast with the menstrual cycle. Am J Pathol. 1981;104:23–34.
2 Longacre TA, Bartow SA. A correlative morphologic study of human breast and endometrium in menstrual cycle. Am J Surg Pathol. 1986;10(6):382–393.
3 Hughes LE, et al. Aberrations of normal development and involution (ANDI): a new perspective on pathogenesis and nomenclature of benign breast disorders. Lancet. 1987;2(8571):1316–1319.
4 Gram IT, Funkhouser E, Tabár L. The Tabár classification of mammographic parenchymal patterns. Eur J Radiol. 1997;24:131–136.
5 Tot T, Tabár L, Dean PB. The pressing need for better histologic-mammographic correlation of the many variations in human breast anatomy. Virchows Arch. 2000;437:338–344.
6 Tabár L, Dean PB, Tot T. Teaching atlas of mammography. 3rd ed. Stuttgart, New York: Georg Thieme Verlag; 2001.
Chapter 2
General Morphology of Breast Lesions
Most pathologic processes in the breast originate in the terminal ductal-lobular units (TDLUs). The affected TDLUs are distended, distorted, or destroyed by the accumulation of fluid, mucin, cancer cells, necrotic debris, or calcium in the lumina of the acini and of the terminal duct or by the accumulation of collagen, glycoproteins, or stromal cells in the intralobular stroma (Fig. 2.1, thick-section image).
Fig. 2.1
If the pathologic process primarily distends and distorts the TDLU, spherical or oval lesions develop (Fig. 2.2, thick-section image).
Fig. 2.2
If the pathologic process destroys and replaces the pre-existent TDLU, a stellate lesion may develop (Fig. 2.3, thick-section image).
