Mucocele-like Lesions: Radiologic-Pathologic Correlation

Mucocele-like lesions (MLLs) of the breast are rare lesions described as dilated, mucin-filled cysts associated with rupture and extracellular mucin in the surrounding stroma. These lesions are of clinical concern because they can coexist with a spectrum of atypical and malignant findings, including atypical ductal hyperplasia, ductal carcinoma in situ, and invasive carcinoma including mucinous carcinoma. Imaging findings of MLLs are nonspecific and varied, although the most common initial finding is that of incidental coarse heterogeneous calcifications on mammography. Occasionally, an asymmetry or mass may be found with or without calcifications, and such MLLs have a higher rate of upgrade to malignancy at excision. Pathology findings are often descriptive given the small sample received from percutaneous biopsy, and the primary consideration is to report any associated atypia, including atypical ductal hyperplasia. There is consensus in the literature that MLLs with atypia on biopsy should undergo excision because of the average reported 17.5% (20/114) upgrade rate to malignancy. The upgrade rate for MLLs without atypia averages 4.1% (14/341). Therefore, imaging surveillance may be a reasonable alternative to excision for MLLs with no atypia on a case-by-case basis. We review MLL imaging findings, pathology findings, and clinical management and present 3 cases from our institution to add to the literature on these rare lesions.

Spectrum of Mucin-containing Lesions of the Breast: Multimodality Imaging Review with Pathologic Correlation

Mucin-containing lesions of the breast encompass a wide range of benign and malignant processes. The spectrum of histologic findings includes incidental mucus-filled benign cysts or ducts, mucocele-like lesions (MLLs), mucin-producing ductal carcinoma in situ, and invasive mucinous carcinoma. MLL is characterized by the presence of mucin-containing cysts that are typically associated with extravasated stromal mucin. MLL is often benign but can be associated with epithelial atypia or malignancy. Mucinous carcinoma represents the malignant end of the spectrum of mucinous lesions of the breast. Evidence-based literature supports a conservative approach for benign MLLs without associated atypia or malignancy, reserving excision for those lesions exhibiting such pathologic features. The most common imaging finding for MLL is microcalcifications at mammography. No specific imaging feature is predictive of malignant outcome at surgical excision. Invasive mucinous carcinoma is a heterogeneous breast tumor subtype, as defined according to the World Health Organization criteria. Mucinous carcinomas are categorized into pure (>90% mucinous component) or mixed (10%-90% mucinous component) subtypes. Pure mucinous carcinomas are generally associated with excellent prognosis and survival, with a few exceptions. Mixed mucinous carcinomas do not have the same favorable prognosis and instead behave similarly to invasive breast carcinomas of no special type. Characteristic diagnostic imaging features can be identified for mucinous carcinoma based on its mucinous and nonmucinous contents. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Mucin Neovascularization as a Diagnostic Aid to Distinguish Mucinous Carcinomas From Mucocele-like Lesions in Breast Core Needle Biopsies

The distinction between mucinous carcinomas (MCs) and mucocele-like lesions (MLLs), particularly those containing detached epithelial fragments, can be problematic in the limited samples afforded by breast core needle biopsies (CNBs). Neovascularization of mucin has been proposed as a criterion to distinguish MC from MLL, but its value in helping to categorize mucin-producing breast lesions in CNB has not been previously investigated. To address this, we evaluated mucin neovascularization on hematoxylin and eosin (H&E)-stained sections of 140 CNB containing mucin-producing breast lesions including 52 MC, 17 mucin-producing ductal carcinoma in situ (mDCIS), and 71 MLL. In 116 cases with sufficient remaining material (42 MC, 16 mDCIS, and 58 MLL), we also assessed mucin neovascularization on CD31 immunostains. On H&E-stained sections, neovascularization of mucin, defined as delicate, thin-walled microvessels in mucin, and unassociated with fibrous septae, was identified significantly more frequently in MC than in MLL (69.2% vs. 14.1%; P=0.0001). The difference in the frequency of mucin neovascularization between MC and MLL was even greater on CD31 immunostains (97.6% vs. 13.8%, P<0.00001). The sensitivity, specificity, positive predictive value, and negative predictive value of mucin neovascularization for categorizing a lesion as MC were 69.2%, 85.8%, 78.3%, and 79.2%, respectively, for H&E-stained sections and 97.6%, 86.2%, 83.7%, and 98.0%, respectively, for CD31 immunostains. We conclude that mucin neovascularization is significantly more common in MC than in MLL in breast CNB on H&E-stained sections and particularly on CD31 immunostains and may be a valuable adjunct in distinguishing between MC and MLL in problematic cases.

Mucocele-like lesions of the breast - A radiological and clinicopathological analysis

INTRODUCTION

Mucocele-like lesions (MLL) of the breast are rare entities which are considered to harbor uncertain malignant potential. Current UK guidelines recommend vacuum assisted excision (VAE) of all such lesions regardless of whether they display epithelial atypia. This study sought to review the key histological and radiological features of MLLs and compare their differing outcomes based on the presence of epithelial atypia.

METHODS

Pathology records of a single breast cancer screening center were retrospectively searched for all biopsy diagnosed MLLs over an 11-year period. Upgrade rates to malignancy (positive predictive values) were calculated by reviewing histology from the initial core biopsy and comparing with the corresponding excision specimen. Radiological images were simultaneously reviewed to provide radiological-pathological correlation.

RESULTS

Three of 11 patients (27.3%) with atypical MLLs on biopsy had malignant outcomes at excision, compared with only 1 of 36 patients (2.8%) with non-atypical MLLs. The majority of MLLs (93%) were identified as microcalcifications on mammographic imaging. No specific radiological features were predictive of malignancy.

CONCLUSIONS

Our data suggest that MLLs without atypia are potentially overtreated with current protocols and could be managed conservatively with radiological follow up. Radiological-pathological correlation is essential.

Mucocele-like Lesion of the Breast Diagnosed on Core Biopsy: Histologic and Clinical Analysis of 78 Cases With Focus on Features Associated With Upgrade

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.

Unusual Changing Calcification Patterns on the Mammogram in a Pure Mucocele-Like Lesion of the Breast: A Case Report

Patient: Female, 39

Final Diagnosis: Mucocele-like lesion

Symptoms: None

Medication: —

Clinical Procedure: —

Specialty: Radiology

Clinical Management of Mucocele-Like Lesions of the Breast with Limited or no Epithelial Atypia on Core Biopsy: Experience from Two Institutions

PURPOSE

Mucocele-like lesions of the breast identified on core biopsy are rare high-risk lesions associated with variable upgrade rates to carcinoma on excision. We aimed to identify the clinicoradiopathological features that can help optimize management of this lesion.

METHODS

We evaluated 50 mucocele-like lesions identified on core biopsies from two institutions, including 36 with no atypia and 14 with limited atypia. Outcome data from excision or clinicoradiological follow-up were reviewed with core biopsy results.

RESULTS

Radiological targets were calcifications in 74% of cases, calcifications with associated mass or density in 16%, and mass in 10%. One of the 16 excised lesions without atypia on core biopsy, which was a mass lesion, was upgraded to mucinous carcinoma on excision. Of the 12 excised lesions with limited atypia, none were upgraded on excision. Among the lesions not excised, 20 without atypia had a median follow-up of 61 months, and 2 with limited atypia had follow-up of 97 and 109 months. None of these 22 patients had new development of their lesions on follow-up. The upgrade rate was 2% in our entire cohort, 3% for lesions without atypia, and 0% for lesions with limited atypia.

CONCLUSIONS

Clinicoradiological surveillance can be appropriate when a mucocele-like lesion without atypia is identified on core biopsy for a non-mass lesion with pathological-radiological concordance. For mucocele-like lesions with limited atypia, a nonsurgical approach could be considered if the atypia by itself does not warrant excision. The latter recommendation requires careful clinicopathological correlation and support from additional studies.

Mucocele like Tumour of the Breast Associated with Ductal Carcinoma in situ and Focal Ductal Carcinoma: What is the Best Approach to these Patients?

Mucocele Like Tumours (MLT) of the breast are quite rare neoplasms displaying a broad spectrum. These lesions were considered benign initially. But now, they are believed to be related to atypical ductal hyperplasia, ductal carcinoma, or mucinous carcinoma. Preoperative diagnosis in fine needle aspiration and core biopsy is difficult. We are reporting a case of mucocele like tumour with ductal carcinoma in situ and ductal carcinoma in a 71-year-old Turkish woman. The patient had a palpable mass in her left breast. Mammograpy showed ill defined and lobulated mass with widespread tiny microcalcifications. A few cells with sporadic nuclear atypia, were detected on FNAB (Fine Needle Aspiration Biopsy). Mastectomy was done on the left side because of the suspicion of malignancy as evident by mammograpy and FNAB. We examined adequate tissue samples from resection material. Histopathologic findings were consistent with MLT and microscopic focus of ductal carcinoma was also noted in mastectomy specimen. She is currently disease-free in the 118^th month. We believe that our case will be the first patient from Turkey and will be added to the database as one of the longest term follow-up MLT cases reported. If a mucocele-like tumour is suspected in fine needle biopsy, surgical excision should be recommended and the specimen should be carefully evaluated to exclude the presence of ductal carcinoma in situ or carcinoma.

Mucocele-Like Lesions of the Breast: Rate of Upstaging and Cancer Development

BACKGROUND

Breast mucocele-like lesions (MLLs) are rare breast lesions. There is a paucity of literature on the rate of pathologic upstaging of MLL to in situ or invasive breast cancer. We sought to review our experience with MLL at a tertiary care center and review published literature.

METHODS

A retrospective review was undertaken of all patients with breast MLL at the Mayo Clinic, Rochester, from 1998 to 2016. Descriptive statistics were performed.

RESULTS

Overall, 30 patients were diagnosed with MLL, with a mean age of 54.6 years (range 51-58). Calcifications on screening mammogram were the most common method of MLL detection (n = 26, 86.7 %), with core needle biopsy (CNB) being performed in 29/30 patients. MLL with atypia was identified in 14 patients (48 %), and surgical excision was performed in 26 patients. Disease was upstaged to invasive disease in one patient (3.8 %) who presented with a palpable mass. With a median duration of follow up of 3.5 years [interquartile range 1-7.1], two patients developed contralateral invasive breast cancer (both patients had a remote history of invasive breast cancer on that side), and one patient developed contralateral in situ disease. Review of the literature demonstrates a 2.9 % upgrade rate of MLL without atypia on excisional biopsy.

CONCLUSIONS

The upstage rate of MLL identified on CNB to invasive disease at surgical excision in this series was 3.8 %. In cases with MLL presenting as calcifications, no cases were upstaged in this series. Across the literature, upstage rates of MLL without atypia on CNB are low, indicating excisional biopsy may be avoided in these cases.