Multimodal imaging pitfalls in differentiating unilateral plasma cell mastitis from breast cancer: a case description

Introduction

Plasma cell mastitis (PCM) is a rare, benign inflammatory breast condition that can mimic breast cancer clinically and radiologically (1). The accurate differentiation between PCM and breast cancer is crucial due to their overlapping features on imaging studies. Multimodal imaging techniques, including ultrasound, mammography, and magnetic resonance imaging (MRI), play a vital role in initial assessment but have limitations in distinguishing inflammatory processes from malignancies (2,3). This case study analyzes an instance of unilateral PCM misdiagnosed as breast cancer, focusing specifically on the pitfalls of various imaging modalities in the diagnostic process. By examining the limitations and potential misinterpretations of each imaging technique, we aim to enhance clinician awareness of these diagnostic challenges and improve the accuracy of PCM diagnosis.

Case presentation

Patient demographics and clinical history

A 31-year-old female presented to our hospital on March 4, 2024, with a quail egg-sized, palpable mass in her right breast discovered incidentally five days prior. The mass was asymptomatic, without local or systemic symptoms. The patient had two previous childbirths (February 2017 and January 2020) with completed breastfeeding. Her medical history was unremarkable, with no family history of breast or ovarian cancer. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was provided by the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Initial presentation and physical examination

Physical examination revealed a visible elevation in the upper inner quadrant of the right breast, with normal bilateral breast skin and nipples. Two distinct masses were palpated in the right breast: a 4 cm × 3 cm mass at 1 o’clock and a 2 cm × 1 cm mass at 10 o’clock, both firm, irregular, ill-defined, moderately mobile, and non-tender. A mildly enlarged lymph node (1 cm × 0.5 cm) was palpable in the right axilla. These findings suggested a complex breast pathology, raising concerns for potential malignancy despite the patient’s young age and absence of inflammatory signs, necessitating further diagnostic investigations.

Imaging examinations

Breast ultrasound examination

Ultrasonography of the right breast revealed: (I) a well-circumscribed, oval hypoechoic lesion (7 mm × 5 mm × 4 mm) at 3 o’clock; (II) two irregular hypoechoic areas: two at 2 o’clock (19 mm × 5 mm) and one at 10–11 o’clock (29 mm × 5 mm); (III) an oval hypoechoic nodule (10 mm × 4 mm) in the right axilla with mild cortical thickening (Figure 1). Findings were categorized as Breast Imaging Reporting and Data System (BI-RADS) 4A, indicating low suspicion for malignancy but warranting further investigation.

Figure 1 Ultrasonographic findings of the patient with PCM in the right breast. Ultrasonography of the right breast revealed several hypoechoic lesions, including a well-circumscribed, oval hypoechoic lesion at the 3 o’clock position (yellow arrow, A), two irregular hypoechoic areas at the 2 o’clock (yellow arrow, B), 10–11 o’clock positions (yellow arrow, C), and an oval hypoechoic nodule with mild cortical thickening in the right axilla (yellow arrow, D). PCM, plasma cell mastitis.

Mammography

Mammography revealed extremely dense breast tissue (BI-RADS density category “d”), characterized by extensive fibroglandular tissue throughout the breast with minimal fatty tissue. In the upper outer quadrant of the right breast, a poorly defined oval nodule (12 mm × 10 mm) was detected (Figure 2). Scattered punctate calcifications were observed in both breasts. An enlarged lymph node (11 mm × 8 mm) was identified in the right axilla. Although a benign condition is more likely, malignancy cannot be excluded; thus, a biopsy is warranted (BI-RADS 4A). The enlarged right axillary lymph node requires further evaluation. Scattered benign calcifications in both breasts suggest follow-up (BI-RADS 2). The high breast density poses a diagnostic challenge by potentially obscuring lesions, necessitating correlation with additional imaging modalities for comprehensive assessment.

Figure 2 Mammographic findings of the patient with PCM in the right breast. Mammography revealed extremely dense breast tissue (category “d”) with a poorly defined oval nodule in the upper outer quadrant of the right breast on the CC view (yellow arrow, A) and MLO view (yellow arrow, B). An enlarged lymph node is identified in the right axilla (B). Scattered punctate calcifications are observed in both breasts (A-D). CC, cranial-caudal; L, left; MLO, mediolateral oblique; PCM, plasma cell mastitis; R, right.

Breast MRI examination

Breast MRI revealed dense glandular tissue bilaterally with mild parenchymal enhancement post-contrast. The right breast showed multiple irregular signal abnormalities: hyperintense on T2-weighted image (T2WI), iso-intense on T1-weighted image (T1WI). Notably, post-contrast images displayed non-mass-like enhancement with clustered ring patterns, irregular margins, and potential spiculations. The time-intensity curve (TIC) showed rapid initial enhancement with washout/plateau. Diffusion-weighted imaging (DWI) showed heterogeneous hyperintensity [apparent diffusion coefficient (ADC): 1.035×10⁻³ mm²/s]. The most extensive lesion (54 mm × 46 mm) abutted the right pectoralis major muscle. An enlarged right axillary lymph node (10 mm × 5 mm) was noted. The left breast appeared normal (Figure 3). Right breast findings, particularly the non-mass-like enhancement with clustered ring patterns, were highly suspicious for carcinoma (BI-RADS 5), with possible axillary metastasis. Left breast: BI-RADS 1. These MRI findings strongly suggest malignancy in the right breast, warranting histopathological correlation for definitive diagnosis.

Figure 3 MRI findings of the patient with PCM in the right breast. The right breast showed multiple irregular signal abnormalities, isointensity on T1WI (yellow arrow, A) and T2WI (yellow arrow, B), with non-mass-like enhancement and clustered ring patterns on DCE MRI (yellow arrow, C). DWI showed heterogeneous hyperintensity (yellow arrow, D) with heterogeneous hypointensity on the ADC map (E). The time-intensity curve showed rapid initial enhancement with washout/plateau (F). ADC, apparent diffusion coefficient; DCE, dynamic contrast-enhancement; DWI, diffusion-weighted imaging; MRI, magnetic resonance imaging; PCM, plasma cell mastitis; T1WI, T1-weighted imaging; T2WI, T2-weighted imaging.

Pathological examination

Core needle biopsy of the right breast lesions at 10 and 1 o’clock positions showed peri-lobular infiltration of plasma cells, with focal lymphocytic and eosinophilic infiltration. This was consistent with PCM, which is a distinct chronic benign inflammatory breast disease.

Treatment and follow-up

After two months of standard treatment for PCM with limited improvement, the patient opted for traditional Chinese medicine therapy based on personal preference. At follow-up on May 1, 2025, the patient reported complete resolution of the right breast mass and absence of other symptoms. No follow-up imaging was performed at our institution.

Discussion

In this case, the misdiagnosis of PCM as breast cancer highlights several critical imaging pitfalls. These pitfalls underscore the challenges in differentiating inflammatory breast conditions from malignancies using multimodal imaging techniques. The limitations of current imaging modalities were highlighted by this misdiagnosis, which emphasizes the need for a comprehensive diagnostic approach that integrates clinical, radiological, and pathological findings.

Imaging characteristics and diagnostic challenges

Ultrasound findings in this case demonstrated multiple hypoechoic masses with irregular morphology, consistent with typical PCM presentations. However, the presence of a well-circumscribed, oval hypoechoic lesion introduced diagnostic ambiguity, leading to a BI-RADS 4A classification. This aligns with previous reports where PCM mimicked breast cancer due to irregular hypoechoic masses (4). A recent study by Hu et al. (3) evaluated the diagnostic value of combining ultrasonography and mammography for PCM. Their retrospective analysis of 111 patients with histopathologically confirmed PCM showed that ultrasonography alone identified only 82.0% of cases, indicating a significant potential for misdiagnosis when used in isolation. This highlights the necessity of integrating mammography with ultrasonography to improve diagnostic accuracy. The combination of both imaging modalities achieved a diagnostic accuracy of 91.9%, significantly higher than using either modality alone (P<0.05). Moreover, some technical limitations of ultrasound deserve attention. Conventional probes may underestimate superficial PCM, as subtle features can be missed due to limited resolution. Recent evidence underscores the benefit of using high-frequency transducers (≥15 MHz), which substantially improve the visualization of superficial breast lesions. It can provide more accurate delineation in cases of superficial PCM (5). Conversely, for deeply located or chest wall-adjacent lesions, ultrasound may be limited by the acoustic window and tissue penetration. Recent pictorial reviews emphasize that when extension into the deep mammary portion or chest wall is suspected, standard ultrasound may be insufficient, and second-level imaging, such as MRI, should be considered to avoid diagnostic pitfalls (6).

Dense breast tissue is a common challenge for mammography. In this case, the patient’s dense breast, combined with reliance on a poorly defined oval nodule and the absence of typical malignant microcalcifications, contributed to the misdiagnosis of BI-RADS 4A. These limitations further highlight the need to consider additional imaging modalities, such as MRI, to enhance diagnostic accuracy.

MRI findings significantly contributed to the diagnostic complexity for this case. The presence of non-mass enhancement with clustered ring patterns—a feature often associated with malignancy—led to misclassification as BI-RADS 5, although such findings can also occur in PCM (2). A critical oversight was failing to recognize the mismatch between the enhancing regions and areas of low ADC, which can help differentiate inflammatory lesions from malignant tumors (7). Furthermore, the rapid initial enhancement with a plateau on the TIC is another pattern that can be seen in both conditions and adds to the diagnostic challenge. These factors collectively highlight the limitations of conventional MRI interpretation in definitively distinguishing between inflammatory conditions like PCM and malignancies. A recent study by Peng et al. (8) developed a diagnostic model to differentiate non-lactational mastitis (NLM), including its subtypes such as PCM, from breast cancer using ultrasound and MRI features. The model included factors like age, blood flow, calcification, lesion margins, enhancement patterns, ADC values, and TIC types. It achieved an area under the curve (AUC) of 0.920, demonstrating high accuracy in distinguishing NLM from breast cancer. This underscores the importance of integrating multiple imaging features to improve diagnostic precision.

Critical analysis of diagnostic pitfalls

The misdiagnosis in this case can be attributed to several factors:

• Overreliance on “classic” malignant imaging features, particularly from MRI.
• Insufficient integration of findings across multiple imaging modalities.
• Inadequate consideration of the patient’s clinical presentation and risk factors.

The inherent limitations of imaging techniques in differentiating inflammatory conditions from malignancies in dense breast tissue are significant.

These pitfalls underscore the need for a more holistic approach to breast lesion diagnosis, incorporating clinical, radiological, and pathological findings (9).

Strategies for enhancing diagnostic accuracy

To improve diagnostic accuracy in differentiating PCM from breast cancer, we propose the following strategies:

• Optimization of multimodal imaging techniques: integrate findings from ultrasound, mammography, and MRI, with a focus on identifying features specific to inflammatory processes.
• Clinical correlation and histopathological confirmation: interpret imaging findings in the context of clinical presentation, considering factors such as the absence of systemic symptoms. Histopathological examination remains the gold standard for diagnosis, particularly when imaging results are ambiguous (10). From a pathological perspective, PCM is often confused with both breast cancer and granulomatous lobular mastitis (GLM). PCM and GLM are distinct entities: PCM features periductal plasma cell infiltration with mammary duct ectasia, while GLM presents as granulomatous inflammation in breast lobules with epithelioid histiocytes and multinucleated giant cells (10). Recognizing these pathological differences is crucial for accurate diagnosis and management.
• Advanced imaging protocols: develop and implement specialized imaging protocols for cases where standard techniques yield inconclusive results (11).
• Machine learning and artificial intelligence (AI): explore the potential of AI algorithms in improving the accuracy of image interpretation and reducing the risk of misdiagnosis.

Implications for clinical practice and future research

This case serves as a crucial reminder of the limitations of imaging in definitively diagnosing breast lesions. It highlights the critical importance of histopathological confirmation, particularly in cases where imaging findings suggest malignancy but are not entirely typical. Clinicians should maintain a high index of suspicion for inflammatory conditions like PCM, especially in patients with dense breast tissue where imaging interpretation is challenging. A significant limitation of this case is the lack of follow-up imaging, making it impossible to entirely exclude lesion persistence or recurrence despite clinical improvement.

Conclusions

In conclusion, this case report underscores the complexities involved in differentiating PCM from breast cancer using current multimodal imaging techniques. By highlighting these diagnostic pitfalls, we aim to enhance clinician awareness and promote more accurate diagnoses of breast lesions. The integration of clinical, radiological, and pathological findings remains crucial in navigating the challenges posed by conditions like PCM, ultimately leading to improved patient care and outcomes.

Acknowledgments

None.

Footnote

Funding: This work was supported by the Shenzhen Yantian District Science and Technology Program (grant No. YTWS20240201) to P.Q.W., and the Guangdong Provincial Science and the Guangdong Provincial Science and Technology Program Project (Guangdong-Hong Kong-Macao Joint Innovation Field) (grant No. 2024A0505040005) to Y.B.L.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1033/coif). P.Q.W. reports that this research was supported by the Shenzhen Yantian District Science and Technology Program (grant No. YTWS20240201). Y.B.L. reports that this work was funded by the Guangdong Provincial Science and Technology Program Project (Guangdong-Hong Kong-Macao Joint Innovation Field) (grant No. 2024A0505040005). The other author has no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was provided by the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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