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

carcinoma in almost all tubular carcinomas. It is typically a peculiar low-grade in situ
carcinoma with a clinging or micropapillary pattern, yet cribriform patterns or
mixtures of the two occur as well (11,23). Coexistent lobular carcinoma in situ has
been found in from 1% to 23% of patients with tubular carcinoma (14,11,18). LCIS is
more common in cases of tubuloloular carcinoma (42). Foci of atypical lobular hyperplasia
are also not unusual. Tubular/cribriform carcinoma does not elicit a marked
lymphocytic reaction, and lymphatic-vascular invasion is extremely rare.
Differential diagnosis: Because of the extremely good prognosis of tubular
carcinoma, one could debate the utility of separating it from benign mimics.
Nonetheless, the distinction between tubular carcinoma and sclerosing adenosis can be
a challenging diagnostic problem. The proliferative pattern of sclerosing adenosis is
lobulocentric, and at low magnification it is almost always possible to perceive
individual altered lobules in the lesion. Tubular/cribriform carcinomas do not have a
lobulocentric configuration, although it can be multifocal. Individual foci of sclerosing
adenosis are composed of elongated and largely compressed glands with interlacing
spindled myoepithelial cells. Varying numbers of more dispersed round, oval, or
angular glands are present in some cases, which have been described as tubular
adenosis. Proliferation of myoepithelial cells is a regular feature of sclerosing
adenosis while these cells are absent in tubular carcinoma. Both lesions may be
present in fat. Cribriform areas may also be found in adenoid cystic carcinomas when
gland formation is more prominent than cylindromatous elements. They are part of
the spectrum of adenoid cystic carcinoma (24).
Microglandular adenosis resembles normal breast or an ill-defined, indurated area of
gray-white, fibrofatty breast (essentially identical to that of fibrocystic changes, not
otherwise specified). Most lesions are 3 to 4 cm in diameter, but can range from an
incidental microscopic focus to 20-cm lesions (23,30-33). Microglandular adenosis
can mimic invasive, well-differentiated (tubular) carcinoma (23,25-29).
Microglandular adenosis is a proliferation of small uniform glands, which grow in a
haphazard and diffuse fashion in the breast parenchyma (23, 30-33, 42). Although
currently considered benign in most instances, some investigators believe that
microglandular adenosis may be a precancerous lesion (30,33). This lesion has
features of both benign sclerosing adenosis and invasive well-differentiated (tubular)
carcinoma, with which it might be confused (23,30-33). In one series of 11 patients
with microglandular adenosis, two patients were inappropriately treated with
mastectomy (32). Typical microglandular adenosis is treatable with excision biopsy,
since no metastasis of microglandular adenosis has yet been documented (32).
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