Distinct clinicopathological and genomic features in solid and basaloid adenoid cystic carcinoma of the breast

Abstract

Adenoid cystic carcinoma (AdCC) of the breast is a rare indolent carcinoma of salivary gland-type tumors, frequently associated with MYB genetic alteration. Solid and basaloid adenoid cystic carcinoma (SB-AdCC) is considered a sparse variant of AdCC. This study sought to search for clinicopathological and genomic features in SB-AdCC. Registered clinicopathological data on a cohort of 13 AdCC of the breast cases, including six conventional adenoid cystic carcinoma (C-AdCC) cases and seven SB-AdCC cases, were collected. MYB gene rearrangement via fluorescent in situ hybridization was investigated and MYB protein expression was evaluated by immunohistochemistry. Compared with C-AdCC, we found that the distribution of SB-AdCC cases were shifted to older age and were more frequently distant metastasis. Moreover, metastasis cases also showed a high (exceed 30%) Ki-67 index. Both groups showed MYB rearrangements and MYB protein expression, but they were less frequent in SB-AdCC than C-AdCC. To conclude, our results suggest that SB-AdCC is an aggressive variant of mammary AdCC with a higher incidence of distant metastases compared with C-AdCC, though they share common molecular features. A high Ki-67 index may be an adverse prognostic factor for metastasis.

The Role of Novel Immunohistochemical Markers for Special Types of Breast Carcinoma

“…In studies analyzing only breast AdCC, the MYB IHC positivity ranges from 60% to 100%. 6,[11][12][13][14] Poling et al 14 found 100% (11/11) of breast AdCCs showed diffuse, moderate to strong MYB labeling, predominantly localized in the myoepithelial cell component. The authors compared this to other breast neoplasms and found only focal, weak expression in 63% (10/16) of TNBCs and 71% (5/7) of collagenous spherulosis cases, whereas no (0/5) cases of microglandular adenosis (MGA) were positive for MYB.…”

“…It should be stated that although the MYB translocation can also be evaluated by fluorescence in situ hybridization (FISH), with detection rates ranging from 22.6% to 89%, the reported rate of MYB IHC expression is routinely higher than the detection of MYB rearrangement by FISH. 6,8,11,13,14 These findings should be unsurprising as the identification of multiple mechanisms leading to MYB overexpression limits the sensitivity of FISH testing. In addition, MYB rearrangement detected by FISH has been reported in 4% of non-AdCC breast neoplasms, both benign and malignant.…”

“…All the non-AdCC tumors were negative for the MYB-NFIB fusion. In studies analyzing only breast AdCC, the MYB IHC positivity ranges from 60% to 100% 6,11–14 . Poling et al 14 found 100% (11/11) of breast AdCCs showed diffuse, moderate to strong MYB labeling, predominantly localized in the myoepithelial cell component.…”

Optimal surgical procedure for treating early-stage adenoid cystic carcinoma of the breast

“…Breast cancer is the most common malignant tumor in women 1 ; there were approximately 2.3 million new breast cancer cases and 685,000 breast cancer deaths worldwide in 2020 2 . Of these cases, adenoid cystic carcinoma of the breast (BACC) accounts for less than 0.1% 3 . Most of these tumors exhibit indolent clinical behavior with a low tendency for axillary lymph node involvement and distant metastasis, showing significant differences from other pathologic types.…”