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

Adenoid cystic carcinoma (AdCC) is clearly a tumour with adenomyoepithelial
differentiation and characterized by the presence of a dual population of basaloid and
luminal cells arranged in specific growth patterns. These adenomyoepithelial features
are unscored by Van Dorpe and coworkers who reported a case of adenoid cystic
carcinoma arising in a tubular adenomyoepithelioma (8).
AdCCs, regardless of the anatomical site, are characterized by expression of the protooncogene
and therapeutic target c-KIT, and seem to harbor a specific chromosomal
translocation t(6;9) leading to the fusion gene MYB-NFIB and overexpression of the
oncogene MYB. However, as already noted the clinical behavior of salivary gland and
breast AdCC differs; while salivary gland lesions have a relatively high proclivity to
metastasize, patients with breast AdCCs have an excellent outcome (9).
Mastectomy has been curative in the vast majority of cases (1, 3-6, 10-14); but, chest
wall recurrence has been reported after simple mastectomy (14). Moreover, there can
be isolated systemic metastases, which occur in ~10% of cases (2, 10, 15-18). This
contrasts with a ~43% distant metastasis rate for salivary gland adenoid cystic
carcinoma (18). In a review of ~100 cases of adenoid cystic carcinoma of the breast,
there were only 12 with distant metastases. Pulmonary metastases are by far the most
common site, and metastases may be detected 6 to 12 years (10, 15, 16, 19) after
finding the primary breast tumor. Other metastatic sites include bone, liver, kidney,
brain, thigh, pleura, mediastinal lymph node, supraclavicular lymph node, and inferior
vena cava (2, 20). Many patients with systemic metastases will have negative axillary
lymph nodes, but axillary metastases may occur (1, 17, 21). In fact, only three cases of
axillary lymph nodal metastases had occurred in ~100 cases reviewed (2). Those with
axillary metastases usually develop pulmonary metastases, and two such cases were
considered to have died of metastatic mammary adenoid cystic carcinoma, but the
diagnosis was not well established in one of the cases (17). This metastatic pattern
clearly suggests that hematogenous spread is most common and that the clinical
course is very slow with symptoms developing years after primary diagnosis.
Moreover, surgical resection of these metachronous metastases has been successful in
maintaining disease control (2, 18).
Adenoid cystic carcinoma occurs in adult women of the same age group as for
mammary carcinoma (i.e., mean ages 50 to 63 years; range 25 to 80 years of age) (2,
3, 5, 6, 10-12, 22). Adenoid cystic carcinoma usually presents as discrete, firm
masses. Uncommonly, they are detected by mammography (12). They can present
“acutely” but some have been present for 10 years or more (11). Most are hormone
receptor negative (12, 22, 23). Sizes vary from 0.2 to 12 cm with most between 1 and
70