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Benign Breast Lesions

 
II. MAMMARY DUCT ECTASIA

Duct ectasia is a nonspecific dilatation of the major subareolar ducts with occasional involvement of the smaller ducts, unrelated to fibrocystic change.

Microscopically, the dilated ducts contain foamy macrophages mixed with lipid material, cholesterol clefts and eosinophilic debris (Slide 28). The material within the ducts often calcifies. Infiltration of lymphocytes, plasma cells, and histiocytes occurs in the periductal tissue. With time, fibrosis increases in amount (Slide 29). Thus terms, such as plasma cell mastitis, obliterative mastitis and comedomastitis, were used. The etiology of the condition is unknown. The theory of an initial inflammatory process leading to destruction of the elastic network and secondary ductal ectasia and periductal fibrosis is favored.


III. BENIGN PAPILLARY NEOPLASM AND CHANGES


A. Intraductal papilloma

Intraductal papilloma usually occurs within a major duct in the subareolar region. When a similar papilloma occurs in the nipple, the term nipple adenoma or papillomatosis is used (see later section).

The clinical presentation is bloody, or serous nipple discharge. The excised lesion is usually small, less than 1-2 cm in size (Slide 30). However, some papillomas are larger than 4 cm, especially those associated with hemorrhage and cystic change. Sometimes the papillomas are multiple involving a group of ducts. Multiple peripheral papillomas are associated with an increased risk for local recurrence and subsequent development of breast carcinoma.

Microscopically, the papillomas form papillary fronds supported by fibrous cores and covered with hyperplastic epithelium (Slides 31 and 32). In addition, solid areas are common, either focal or predominant (Slide 33). The proliferative epithelium is made up of epithelial and myoepithelial cells.

Secondary changes occur often in the form of hemorrhage, infarct, fibrosis and hyalinization, most likely resulting from torsion of the fibrous stalks and ischemic injury. The damaged epithelium and hyalinized stroma may also deposit calcium. In core biopsies, potential diagnostic problems include entrapped ducts in the hyaline stroma interpreted as invasive carcinoma (Slide 34). Nuclear atypia in papillary lesions needs careful evaluation to rule out atypical hyperplasia and ductal carcinoma in situ.

Juvenile papillomatosis refers to a marked ductal hyperplasia in adolescents and young women. The involved ducts are cystically dilated with a Swiss cheese pattern. Atypical ductal hyperplasia and carcinoma may occur (Rosen et al, 1980 and 1985).


B. Radial Scar

Radial scar is a benign lesion known by a variety of names in the literature, including infiltrating epitheliosis, nonencapsulated sclerosing lesion, indurative mastopathy, scleroelastic lesion, sclerosing papillary proliferation, benign sclerosing ductal hyperplasia, and radial sclerosing lesion.

Most radial scars are spiculated masses or areas of architectural distortion, often with multiple long spicules and central areas of lucency.

Radial scar occurs in the background of benign ductal hyperplasia, intraductal papilloma and/or sclerosing adenosis, in which fibrous stromal undergoes fibrosis and elastosis (Slides 35 and 36). As a result, the ducts and ductules become distorted and arranged in a radiating pattern (Slide 35). The ducts entrapped in the scar superficially resemble invasive carcinoma (Slide 36). These benign ducts retain the usual epithelial and myoepithelial cells without significant nuclear atpyia.


III. FIBROEPITHELIAL TUMORS


A. Fibroadenoma

Fibroadenoma is the most common benign breast tumors seen in women under the age of 35 years. The peak age of incidence is in the third decade.

Most fibroadenomas are 2-3 cm in size, but may reach to 6-7 cm, the so called giant fibroadenomas. They are well-circumscribed, but not encapsulated. Cut surfaces have a lobulated, grey-white myxoid, semitransparent to dense fibrous appearance. Cleft-like spaces corresponding to branching ducts may be evident (Slide 37). About 10-20% of fibroadenomas are multiple and bilateral (Slide 38) and may increase in size during pregnancy and undergo infarct following childbirth.

Fibroadenomas consist of epithelial and fibrous components. Branching and budding ducts are surrounded by fibrous tissue. The pericanalicular fibroadenoma maintains round and oval dilated ductal spaces (Slide 39). Whereas in the intracanalicular type, the ductal lumens are compressed by polypoid fibrous stroma creating slit-like irregular spaces. The ducts are lined by two layers of cells: epithelial and myoepithelial cells. Under the influence of hormones, the ducts become hyperplastic with papillary formation and more than two layers of cells.

The fibrous stroma varies from myxoid and hypocellular to fibrous and moderately cellular. Rare mitotic figures may occur, but nuclear atypia is absent or minimal, allowing separation from phyllodes tumor.

Involution is common with increasing age of the lesion. The stroma becomes less cellular, more fibrotic and hyalinized (Slide 40). Coarse calcifications. In old fibroadenomas, the ductal epithelium becomes so atrophic as to disappear completely. Rarely, fibroadenomas enlarge in postmenopausal women, with or without hormone replacement therapy.

Several variants of fibroadenomas have been described. The giant fibroadenoma is simply a fibroadenoma that has reached a large size. Microscopically these are the same as other fibroadenoma, the cellularity can be high.

Tubular adenomas contain predominantly tubular elements and minimal amount of fibrous stroma and sometimes are found during pregnancy. Lactational change may produce a localized mass having enlarged lobules and ducts with vacuolated cytoplasm and secretory product in the lumens.

Very rarely ductal or lobular carcinoma in situ occurs within fibroadenomas (Slides 41 and 42) (Pick and Iossifides). Invasive carcinoma has also been report to arise in a fibroadenoma. When in situ or invasive carcinoma involves the fibroadenoma, about 50% of women also have disease outside of fibroadenoma (Rosen et al, 1993). Thus, it is important to evaluate the surrounding tissue of fibroadenoma to determine the extent of disease for optimal treatment.


B. Phyllodes Tumor (Cystosarcoma Phyllodes)

The malignant counterpart of fibroadenoma is cystosarcoma phyllodes or the newer term of phyllodes tumor, in which the epithelial elements are benign, but the stromal tissue is malignant. It results from malignant degeneration of fibroadenoma, estimated to occur in 1% of patients, who have fibroadenoma for many years.

At presentation, most women are between 40 and 50 years with a typical presentation of a rapidly growing mass.

The phyllodes tumor has a lobulated, leaf-like appearance and varies in size from 1 cm to greater than 15 cm (Slide 43). Microscopically, the branching, hyperplastic ducts are surrounded by a stroma, which is mostly fibrous and much more cellular than fibroadenoma (Slide 44). In addition, nuclear atypia and increased mitotic activity occur (Slides 45 and 46).

The stromal components may contain liposarcoma, leiomyosarcoma, rhabdomyosarcoma, malignant fibrous histiocytoma, angiosarcoma, chondrosarcoma and osteosarcoma. For this reason, it is important to adequately sample the neoplasm to determine whether ductal elements are present. In the absence of epithelial cells, the neoplasm is classified as primary stromal sarcoma of the breast, which is generally more aggressive than phyllodes tumor.

The clinical behavior of phyllodes tumor is unpredictable. The majority of phyllodes tumors are local problems and do not metastasize. Less than 20% of phyllodes tumors metastasize by vascular spread, most commonly to the lung, pleura, and bone. (Hart, 1978; Pietrusz, 1978). Thus, lymph node dissection is not indicated. Local recurrence is likely, if incompletely excised. Therefore, a wide local excision is required.

Some recent studies have attempted to separate cystosarcoma phyllodes into benign and malignant groups. The benign group is characterized by smooth, non-infiltrative borders and the fibrous elements have minimal nuclear atypia and low mitotic activity. This is in contrast to infiltrative borders (Slide 47), presence of nuclear atypia and increased mitotic activity usually greater than five mitotic figures per 10 high power fields in the malignant group (Hart et al; Pietrusz and Barnes). It should be mentioned that not all metastatic phyllodes tumors meet the above criteria. Thus, it is more appropriate to classify the phyllodes tumors into low and high grades and to treat these tumors with wide clear margins.

 
 

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