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

3 cm (3, 10, 12). They are usually circumscribed, but cystic areas occur (12). They are
grey, pale yellow, tan, and pink; and, they are invasive tumors composed of proliferating
glands
(adenoid component) as well as stromal or basement membrane elements ("pseudoglandular"
or cylindromatous component). Typically, in adenoid cystic carcinoma, the
stroma is infiltrated by cell clusters containing features of smaller epithelium-lined
spaces and larger myoepithelium lined cystic spaces. Adenoid cystic carcinoma has
intercellular cystic spaces lined by basement membrane material and biphasic
cellularity with myoepithelial cells intermixed with duct luminal epithelial cells. The
tumor cells do not form apical snouts, but have low-grade nuclei, and often form
delicate arches.
The adenoid parts cause resemblance to cribriform carcinoma; whereas, abundant
stroma mimic scirrhous carcinoma (1, 12, 24). Growth patterns include cribriform,
solid, glandular (tubular), reticular (trabecular), and basaloid areas.
Adenomyoepitheliomatous and syringomatous areas occur (12), and sebaceous
differentiation may be present in ~15% (25). Adenosquamous differentiation is
common as a focal finding (25). Similar to grading of salivary gland adenoid cystic
carcinoma, Ro et al. (1) proposed stratifying adenoid cystic carcinomas into three
grades on the basis of the proportion of solid growth within the lesion (I - no solid
elements; II - less than 30% solid; III - more than 30 percent solid). They found that
tumors with a solid component (grades II and III) tended to be larger than those
without a solid element (grade I) and were more likely to have recurrences. The only
patient who developed metastatic adenoid cystic carcinoma had a grade III lesion. But,
others have not observed this correlation with grade and outcome. Kleer and
coworkers (26) assessed whether histologic features and proliferative activity could
identify aggressive neoplasms. They studied 31 cases of adenoid cystic carcinoma
(age range of patients, 33 to 74 years). Three histologic grades were defined: grade I:
completely glandular; grade II: < 30% solid areas, and grade III: > or = 30% solid
pattern. In 19 of 31 cases, immunohistochemical stains for estrogen receptor were
available. Twelve of 31 cases were immunohistochemically stained for Ki-67 antigen
using MIB1 antibody. Ten of 20 tumors were subareolar. All tumors were grossly
circumscribed; however, 12 of 20 (60%) had focal infiltration peripherally. Five of 19
tumors were estrogen receptor positive. They found no statistical correlation between
MIB1 score and histologic grade, nuclear grade, infiltration of the adjacent fat or
breast parenchyma, or estrogen receptor status. All patients were alive with no
evidence of disease after a median follow-up of 7 years. Neither histologic or nuclear
grading nor proliferative activity was useful prognosticators. None of the tumors had
lymph node metastases. Thus, axillary lymph node dissection may not be necessary.
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