Breast adenoid cystic carcinoma arising in microglandular adenosis: A case report and review of literature

Abstract

BACKGROUND

Breast adenoid cystic carcinoma (AdCC) is a rare invasive carcinoma composed of epithelial and myoepithelial cells. Microglandular adenosis (MGA) is a rare benign proliferative lesion consisting of small, uniform, and round glands formed by a single layer of epithelial cells and basement membrane without a myoepithelial cell layer. MGA may progress to atypical MGA and carcinoma arising in MGA. Among various invasive carcinomas from MGA, AdCC has been rarely reported. Here, we report a case of AdCC arising in MGA.

CASE SUMMARY

A 59-year-old woman was diagnosed with a newly developed density on a routine mammogram. The density was similar to or slightly lower than that of the breast parenchyma. Sonography showed an irregular mass with a slightly higher echo than that of fat. Magnetic resonance imaging showed an irregular mass with a similar T1 signal intensity and a slightly higher T2 signal intensity compared to muscles or the breast parenchyma. The lesion showed heterogeneous internal enhancement with an initially slow and delayed persistent enhancing pattern. Microscopically, the tumor was composed of invasive AdCC, in situ AdCC, and MGA. AdCC is composed of basaloid and ductal epithelial cells forming cribriform or solid sheets, or haphazardly scattered small cribriform or tubular glands. MGA showed small glands with a single epithelial lining and retained lumen. S-100 staining was strongly positive in MGA area. The patient underwent breast-conserving surgery with sentinel lymph node biopsy.

CONCLUSION

Breast AdCC arising in MGA showed unique imaging findings that was different from usual invasive cancer.

Keywords: Breast neoplasms; Fibrocystic breast disease; Carcinoma; Adenoid cystic; Case report

Core Tip: Many pathological or clinical studies have been reported for adenoid cystic carcinoma (AdCC) arising in microglandular adenosis (MGA), but few reports have been reported of radiological findings. In our case, it was characterized by iso- or slight hypo-density in the mammogram and slightly higher echo than that of fat in the ultrasound examination with higher T2 signal intensity and a persistent enhancing pattern in breast magnetic resonance imaging. Although AdCC shows a favorable prognosis and MGA has long been considered a benign entity, there is a risk of MGA becoming malignant and a complete resection should be performed.