Abstract P4-01-01: A case series of the Milky Way sign: A diagnostic finding of ductal carcinoma in situ (DCIS) and invasive breast carcinoma (IDC) on digital breast tomosynthesis (DBT)
Authors: Allison K , Xu Y , Liu YI , Miyake KK , Downey JR , Lipson JA , Ikeda DM 
Published: May 2016

Purpose: we have previously described the "Milky Way Sign", which manifests as microcalcifications overlying noncalcified band-like density, best seen in digital breast tomosynthesis (DBT), in a patient with ductal carcinoma in situ (DCIS). Here, we describe a series of patients with DCIS, IDC, and rarely, Atypical Ductal Hyperplasia (ADH) with this sign.

Materials and Methods: we performed a systemic search of all stereotactic core biopsies for suspicious calcifications performed at our institution from April 15, 2014, when we first implemented DBT with synthesized 2D mammogram, to October 2, 2014, and identified all cases that were diagnosed as DCIS, IDC, or high-risk lesions (such as ADH, atypical lobular hyperplasia (ALH), and intraductal papilloma) on pathology. From 89 biopsied performed in 87 patients, a total of 13 cases of DCIS, IDC, or IDC with DCIS were identified in 12 patients. 17 cases of high-risk lesions were identified in 16 patients, including 10 ADH in 9 patients, 4 ALH, two intraductal papillomas, and one atypical columnar cell change.

Results: Among the 30 cases of suspicious calcifications with a diagnosis of DCIS, IDC, or high-risk lesions, 37% demonstrated the Milky Way Sign (11/30), including 71% of DCIS cases (5/7), 60% of cases of IDC (3/5), 100% of DCIS/IDC (1/1), and 12% of high-risk lesions (2/17). Both high-risk lesions with the Milky Way sign were ADH from the same patient. Among the 11 cases with the Milky Way sign, the breast density at the site of calcifications is either scattered (6/11) or heterogeneously dense (5/11), whereas the density at 1 cm surrounding the calcifications is either fatty (8/11) or scattered (3/11). The breast is less dense surrounding the calcifications in all but one case. The calcifications seen in the Milky Way cases are predominantly fine pleomorphic calcifications except one case of fine linear and linear branching calcifications. The calcifications are grouped (6/11), linear (3/11), or segmental (2/11) in distribution. Five patients also had contrast-enhanced breast MRIs. Among them, three (one each with the diagnosis of DCIS, IDC or DCIS/IDC) had non-mass enhancement on breast MRI that correlated to the Milky Way sign seen on mammogram. The other two patients (one with DCIS and one with IDC) had post biopsy change instead of Non-mass enhancement were seen in the corresponding areas.

Conclusion: The Milky Way sign, in the context of DBT, is a novel diagnostic sign for both DCIS and IDC. It may occasionally be seen in ADH cases as well. Features that often associate with the Milky Way sign include less dense tissue surrounding the calcifications, calcifications that are fine pleomorphic in morphology and grouped or linear in distribution. Preliminary results also suggest that the Milky Way sign may correspond to non-mass enhancement seen on contrast-enhanced breast MRI.

Clinical Relevance Statement: We hope that the Milky Way sign will facilitate detection of both DCIS and IDC in the context of DBT.

Citation Format: Allison K, Xu Y, Liu YI, Miyake KK, Downey JR, Lipson JA, Ikeda DM. A case series of the Milky Way sign: A diagnostic finding of ductal carcinoma in situ (DCIS) and invasive breast carcinoma (IDC) on digital breast tomosynthesis (DBT). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-01-01.