33 Special Types of Invasive Breast Carcinoma: Diagnostic Criteria ...

ich in elastic fibers. The connective-tissue fibers seem to radiate toward the
periphery, where fibrocystic changes are arranged circumferentially and are
characterized by varying combinations of duct hyperplasia, cyst formation, sclerosing
adenosis, and apocrine metaplasia. The central scleroelastotic core may contain small
epithelial nests and glands, which appear distorted and entrapped within the
connective tissue, resulting in a pattern simulating invasive carcinoma
("pseudoinvasion").
Intraductal papillomas are benign, yet clonal, fibroepithelial lesions (21). Most occur
in large ducts where they are usually single, but they also arise in peripheral smaller
ducts where they are multiple in about 10% of cases (41-44). In two large series,
approximately 10% of the benign papillomas had been misdiagnosed as malignant,
sometimes resulting in inappropriate radical surgery (41,42). In the report of Kraus
and Neubecker (42), patients with benign papilloma ranged in age from 16 to 71 years
(average, 39 years). In contrast, patients with papillary carcinoma tended to be slightly
older, with ages at diagnosis ranging from 29 to 78 years (average, 50 years).
Benign papillomas, like papillary carcinomas, present as masses, often near the nipple,
and are sometimes associated with a bloody nipple discharge. These lesions are soft,
friable tumors, usually found within dilated cysts (ectatic ducts). In one series they
measured from 0.5 to 8.0 cm (mean, 2.3 cm) (42). Grossly, papillary carcinomas can
appear similar to intraductal papillomas (42,45). The cysts contain fluid, which may
be bloody or yellow-brown. Microscopically, intraductal papillomas show a
prominent arborescent, fibrovascular core lined by a double layer of epithelial cells
(which is at least focally present in all papillomas). Typically, the core has a
prominent collagenous and/or spindled myoepithelial component. The lining epithelial
cells have normochromatic nuclei and may have areas of apocrine metaplasia and/or
typical duct hyperplasia. Adjacent ducts often have these same features, as well as
areas of sclerosing adenosis. Rarely, focal comedo-like necrosis can occur; indeed, it
is important to know that comedo necrosis is not an absolute indicator of malignancy.
In my experience, among benign lesions, so-called subareolar sclerosing duct
hyperplasia is most prone to contain some comedo necrosis.
Solitary subareolar intraductal papillomas uncommonly display adjacent duct
hyperplasia, atypical duct hyperplasia, and/or carcinoma in situ (43,44); whereas,
papillomas that are peripheral and multifocal are more frequently associated with duct
hyperplasia, and are sometimes atypical and/or carcinomatous (43,44). In fact, some
investigators feel strongly that peripheral duct papillomas are highly susceptible to
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