Mucocele-like Lesion of the Breast Diagnosed on Core Biopsy

Abstract

Context.— Mucocele-like lesion of the breast (MLL) is an uncommon entity, and recent studies show low rates of upgrade from core needle biopsy (CNB) to excision. Objective.— To evaluate features associated with upgrade of MLLs diagnosed on CNB. Design.— Seventy-eight MLLs diagnosed on CNB from 1998–2019 and subsequent excisions were reviewed. Histologic parameters evaluated included the presence of atypia, presence and morphology of calcifications, and morphologic variant (classic [C-MLL], duct ectasia–like [DEL-MLL], or cystic mastopathy–like [CML-MLL]). Results.— Overall, 45 MLLs lacked atypia and 33 were associated with atypia (atypical ductal hyperplasia, 32; atypical lobular hyperplasia, 1). Most were C-MLLs (61) with fewer DEL-MLLs (14) and CML-MLLs (3). Half showed both coarse and fine calcifications, with fewer showing only coarse or fine calcifications, and some showing none. Subsequent excision or clinical follow-up was available for 25 MLLs without atypia—of which 2 (8.0%) were upgraded to ductal carcinoma in situ (DCIS)—and 23 with atypia, of which 4 (17.4%) were upgraded to DCIS. No cases were upgraded to invasive carcinoma. All upgraded cases showed coarse calcifications on CNB, and all upgraded cases were associated with residual calcifications on post-CNB imaging. Conclusions.— Most MLLs present as calcifications and nearly half are associated with atypia. Upgrade to DCIS is twice as frequent in MLLs with atypia versus those without. A predominance of coarse calcifications and the presence of residual targeted calcifications following core biopsy may be associated with higher upgrade rates.

Mucocele-Like Lesion of the Breast

“…However, calcifications may help determine the risk for malignancy. Towne et al reported that all of their MLL cases contained widespread coarse calcifications that were upgraded following CNB, suggesting an association between coarse calcifications and higher upgrade rates [9]. Consistent with previous reports, our patient presented with coarse calcifications on her initial mammogram, and a follow-up ultrasound was recommended.…”

“…However, more recent studies are proposing selective excision based on the histology of the lesion. One study found that MLLs with atypia were upgraded to DCIS twice as often as samples without atypia, occurring in approximately half of the biopsies [9]. Another study found that 28 out of the 53 MLL lesions analyzed were malignant, with 14 being in situ and the other 14 being invasive [13].…”

Breast Mucocele-like lesions (MLL): A case report and review of the literature

“…Ultrasound can demonstrate hypoechoic oval masses, complex cysts with or without associated calcifications, clustered cysts, cysts with thick septations, complex masses (solid-cystic), or tubular masses with low-level internal echoes [10] . There are few reports of mucocele-like cases with magnetic resonance imaging (MRI), being reported as irregular masses with heterogeneous enhancement or nonmass enhancements [ [7] , [11] , [12] ]. There are no specific imaging criteria to predict atypia or malignancy [10] .…”

“…About 11%-57% of the MLLs are associated with ADH [ [3] , [7] ] and 2%-30% are associated with DCIS [3] . The upgrade rate to DCIS for MLL with atypia is 8%-75% and for MLL without atypia is 2.8%-13% ( Table 1 ) [ [5] , [8] , [9] , [11] , [15] , [16] , [17] ]. The atypical hyperplasia can be found outside the area of MLL in 26% of the ADH and 88% of the ALH [4] , reflecting the heterogeneous background of these lesions and reaffirming the importance of a good sampling, not only the visible target.…”

Challenges and Clinical Relevance of Modern Breast Pathology Reporting: Your Questions Answered

“…If the calcifications extend over a significant area on imaging, MDT discussion is needed to determine if excision is needed [78,79]. MLLs associated with atypical epithelial hyperplasia are frequently subjected to excision due to the risk of lesional upgrade reported in up to 15-20% for patients with MLL-associated atypia [76,80,81]. MLLs with DCIS or invasive carcinoma are managed accordingly.…”