Original report. Mucocele-like tumors of the breast: mammographic and sonographic appearances

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

Mucocele-like lesions of the breast are rare, usually presenting themselves as suspicious findings on imaging, warranting biopsies. It can be associated with several degrees of hyperplasia, including atypical ductal hyperplasia and ductal carcinoma in situ, historically being considered a high-risk lesion. It also can be an underestimated invasive carcinoma in a percutaneous biopsy. When facing a histologic diagnosis of a mucocele-lesion in a percutaneous biopsy, it is important to be aware of these lesions' significance to make the most appropriate interpretation, recommendation, and management. The purpose of this work is to present some cases of breast mucocele-like lesions from our Institution and perform a review of the literature.

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.

Mucocele-Like Lesion of the Breast

Mucocele-like lesions (MLLs) of the breast are rare neoplasms characterized by dilated, mucin-filled epithelial ducts or cysts that can rupture and expel their contents into the surrounding stroma. They are frequently associated with atypia, dysplastic change, and, more recently, pre-malignant and malignant conditions like atypical ductal hyperplasia, ductal carcinoma, invasive carcinoma, or mucinous carcinoma. The malignant potential of MLLs is often challenging to determine from the initial histologic evaluation of a core-needle biopsy due to copious mucin and low cellularity. Therefore, at initial presentation, MLLs should be surgically excised and thoroughly evaluated for malignancy. In this paper, we present a rare case of an MLL and explore the radiology, histology, carcinogenic potential, diagnostic evaluation, and suggested management of the condition.

Case Report: Mucocele-Like Tumor of the Breast Associated With Ductal Carcinoma In Situ

Mucocele-like tumor of the breast is histologically characterized as mucin-containing cysts with mucin leaking to the stroma. It could be associated with atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS), and invasive ductal carcinoma (IDC). We report a case of mucocele-like tumor of the breast associated with DCIS confirmed by paraffin section. We review the literature and discuss the imaging features, pathology, and clinical management of the lesion. These lesions demonstrate characteristic imaging features, and we especially highlight the MR characteristics, as they have not been well documented. Performing a diagnostic fine-needle aspiration cytology (FNAC) of mucocele-like tumor carries a risk of tumor underestimation; therefore, excision for all mucocele-like tumors is suggested to be the best approach. However, some recent reports recommend close follow-up for patients with low-risk factors who have mucocele-like tumor without atypia on FNAC.

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

Mucocelelike Lesions in the Breast: Radiologic and Clinicopathologic Correlations With Upgrade Rate

OBJECTIVE

The purpose of this article is to investigate the radiologic and clinicopathologic findings of mucocelelike lesions (MLLs) and the rate of pathologic upgrade with factors predicting it.

MATERIALS AND METHODS

We reviewed our institution's database from January 2006 to December 2012 and enrolled 89 women with 89 MLLs. The pathologic findings from the initial biopsies identified 71 lesions without and 18 lesions with associated high-risk lesions. Images were reviewed according to the BI-RADS lexicon. Clinical and pathologic results were analyzed statistically, and upgrade rates were calculated.

RESULTS

Of the 89 lesions, 67 (75.3%) underwent surgical excision and 22 (24.7%) did not. After surgical excision (n = 67), one lesion was upgraded to mucinous carcinoma, three were upgraded to ductal carcinoma in situ, and 16 were upgraded to MLLs with associated high-risk lesions (29.9% total upgrade rate; 20/67). A statistically significant higher percentage of MLLs with associated high-risk lesions was observed in the surgical excision group (94.4% vs 70.4%; p = 0.036). The final pathologic diagnosis revealed larger lesions (16.4 ± 9.1 vs 12.6 ± 6.8 mm; p = 0.024) and younger patients in the high-risk group (46.9 ± 7.7 vs 50.6 ± 9.1 years; p = 0.049). Although no significant differences were observed in the imaging findings, including the BI-RADS category, upgraded lesions were seen as a mass with calcification as a predominant feature.

CONCLUSION

This study revealed no significant differences in imaging findings or BI-RADS category between high-risk and non-high-risk breast MLLs. However, we confirmed that high-risk lesions typically are seen as larger masses with calcifications.

An Update of Mucinous Lesions of the Breast

Mucinous lesions of the breast include a variety of benign and malignant epithelial processes that display intracytoplasmic or extracellular mucin, including mucocelelike lesions, mucinous carcinoma, solid papillary carcinoma, and other rare subtypes of mucin-producing carcinoma. The most important diagnostic challenge is the finding of free-floating or stromal mucin accumulations for which the significance depends on the clinical, radiologic, and pathologic context. This article emphasizes the differential diagnosis between mucocelelike lesions and mucinous carcinoma, with a brief consideration of potential mimics, such as biphasic and mesenchymal lesions with myxoid stroma ("stromal mucin") and foreign material.

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.

Diagnosis and management of benign, atypical, and indeterminate breast lesions detected on core needle biopsy

Imaging abnormalities detected by mammographic screening often lead to diagnostic evaluations, with suspicious abnormalities subjected to image-guided core needle biopsy (CNB) to exclude malignancy. Most CNBs reveal benign pathological alterations, termed benign breast disease (BBD). Adoption of CNB presents challenges with pathologic classification of breast abnormalities and management of patients with benign or atypical histological findings. Patient management and counseling after CNB diagnosis of BBD depends on postbiopsy determination of radiologic-pathologic concordancy. Communication between radiologists and pathologists is crucial in patient management. Management is dependent on the histological type of BBD. Patients with concordant pathologic imaging results can be reassured of benign biopsy findings and advised about the future risk of developing breast cancer. Surgical consultation is advised for patients with discordant findings, symptomatic patients, and high-risk lesions. This review highlights benign breast lesions that are encountered on CNB and summarizes management strategies. For this review, we conducted a search of PubMed, with no date limitations, and used the following search terms (or a combination of terms): atypical ductal hyperplasia, atypical hyperplasia, atypical lobular hyperplasia, benign breast disease, cellular fibroepithelial lesions, columnar cell lesions, complex sclerosing lesion, core needle biopsy, fibroadenomas, flat epithelial atypia, lobular carcinoma in situ, lobular neoplasia, mucocele-like lesions, phyllodes tumor, pseudoangiomatous stromal hyperplasia, radial scar, and vascular lesions. The selection of references included in this review was based on study relevance and quality. We used additional articles culled from the bibliographies of retrieved articles to examine the published evidence for risk factors of BBD.

Mucocele-like tumor associated with ductal carcinoma in situ diagnosed as mucinous carcinoma by fine-needle aspiration cytology: report of a case

Mucocele-like tumors (MLTs) of the breast are rare, with only 11 cases reported from Japan and 35 cases from other countries. MLTs of the breast were first described by Rosen in 1986. They are believed to be related to atypical ductal hyperplasia, ductal carcinoma, or mucinous carcinoma. It is difficult to diagnose this tumor preoperatively, and especially difficult to differentiate between benign and malignant forms. We report a case of MLT associated with ductal carcinoma in situ, which was initially diagnosed as fibroadenoma by mammography and ultrasonography, and as mucinous carcinoma by fine-needle aspiration cytology. We discuss the characteristic findings of imaging and the appropriate clinical treatment of this tumor. The characteristic image first signals the possibility of this tumor, following which the diagnosis can be confirmed by pathological examination of a fully excised tumor specimen. Breast-conserving surgery is recommended because of the low risk of high-grade malignancy, even when malignancy is confirmed, and lymph node dissection may be avoided.

Mucocelelike Lesions of the Breast: Mammographic Findings with Pathologic Correlation

OBJECTIVE

The purpose of this study was to review the imaging features of mucocelelike breast lesions, correlate the mammographic and pathologic findings, and determine recommendations for management.

CONCLUSION

Mucocelelike lesions are more common than previously reported and are likely to exhibit indeterminate calcifications on mammography. Diagnosis is most often made with Mammotome biopsy. A large number of patients have associated atypia or carcinoma. For patients with purely benign histologic findings at Mammotome biopsy, optimal management should be excisional biopsy to exclude associated malignancy.

Benign and Malignant Mucocele-Like Tumors of the Breast: Mammographic and Sonographic Appearances

OBJECTIVE

The purpose of this study was to analyze and compare the mammographic and sonographic appearances of benign and malignant mucocele-like tumors.

CONCLUSION

The mammographic appearance of mucocele-like tumor of the breast is characterized as pleomorphic calcifications, often increasing in number. Microcalcifications in malignant mucocele-like tumors extended over a wider area than those in benign mucocele-like tumors. Sonography often shows cysts with calcified or noncalcified mural nodules.

Benign mucocele-like lesion of the breast: how to differentiate from mucinous carcinoma before surgery

The aim of the study was to improve the pre-operative diagnosis of mammary mucinous lesions. All mucinous lesions detected by fine needle aspiration (FNA) and confirmed by histological examination were reviewed by cytological findings, mammographic appearances and sonographic findings. Twenty aspirates had corresponding pathology, including 12 mucinous carcinomas, two mucocele-like lesions (MLL) with atypical ductal hyperplasia, three MLL with ductal hyperplasia and three simple MLL. Simple MLL and mucocele-like with ductal hyperplasia showed scant cellularity, no or rare intact single tumour cells, monolayered arrangement and absence of nuclear atypia. In contrast, most mucinous carcinomas showed higher cellularity, more single tumour cells, three-dimensional clusters, and mild to marked nuclear atypia. However, MLL with atypical ductal hyperplasia showed cytological features overlapping with mucinous carcinoma. MLL had a non-specific mammographic appearance and showed a cystic lesion on sonography. Mucinous carcinoma appeared as a solid mass on sonography and as a distinct nodule on mammography. Based on the combination of FNA cytology and image findings, benign MLL can be correctly distinguished from mucinous carcinoma before surgery.

Evolving entities and changing concepts in breast pathology

Among the evolving entities and changing concepts in breast pathology are those relating to columnar cell hyperplasia, pseudoangiomatous stromal hyperplasia, mucocele-like lesions, pleomorphic lobular carcinoma in situ, pseudo-Paget's disease of nipple, microinvasive carcinoma of breast, spindle cell metaplastic carcinoma, and minimal metastatic disease in axillary lymph nodes. Pathologists, as well as physicians involved in the management of breast diseases, need to be aware of these recent developments in breast pathology since the recognition and understanding thereof may have considerable clinical relevance.