Synchronous bilateral breast malignancies: Diagnostic implications of histologic diversity

INTRODUCTION

Synchronous bilateral breast cancer (SBBC) is defined as primary tumors occurring in both breasts, diagnosed concurrently or within a 3–6-months interval. It is relatively uncommon, comprising approximately 1%–2.6% of all breast cancers. SBBC poses diagnostic and therapeutic challenges due to potential differences in tumor biology, hormone receptor status, and histology. Accurate imaging evaluation and histopathologic correlation are crucial in distinguishing multifocal disease from independent primary tumors, as this distinction significantly impacts staging and management decisions. We present a case of SBBC in an elderly woman with distinct histologic subtypes in each breast, emphasizing the diagnostic value of imaging-pathology concordance and the implications for individualized treatment planning.

CASE REPORT

A 75-year-old woman presented with a 1-month history of a palpable lump in the left breast. She had no family history of breast cancer. On examination, a firm, mobile, 4 cm mass was palpated at the 2 o’clock position in the left breast without nipple discharge, skin changes, or retraction. The right breast and bilateral axillae were clinically unremarkable.

Mammography with tomosynthesis revealed a circumscribed, high-density mass in the upper outer quadrant of the left breast. Another spiculated mass with associated architectural distortion was noted in the same quadrant. In the right breast, fine pleomorphic microcalcifications in a segmental distribution and architectural distortion were observed in the lower outer quadrant [Figure 1]. No axillary adenopathy was identified.

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Figure 1: Bilateral full-field digital mammogram shows fine pleomorphic microcalcifications in segmental distribution with architectural distortion in the lower outer quadrant of the right breast extending to the retroareolar region (yellow arrows). Circumscribed high-density mass in the upper outer quadrant of the left breast (green arrows) and another spiculated high-density mass with architectural distortion in the upper outer quadrant of the left breast (red arrows).

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Ultrasound of the right breast demonstrated an ill-defined cluster of prominent ducts with microcalcifications at the 8 o’clock position, showing internal vascularity, categorized as breast imaging reporting and data system (BI-RADS) 4C [Figure 2a]. The left breast showed two separate lesions: at 2 o’clock: an oval, isoechoic mass with internal vascularity corresponding to the palpable concern—BI-RADS 4B [Figure 2b], and at 3 o’clock: an irregular hypoechoic mass with spiculated margins and posterior acoustic shadowing— BI-RADS 4C [Figure 2c].

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Figure 2: (a) Targeted sonography of the right breast: Ill-defined cluster of prominent ducts with microcalcifications at the 8 o’clock position (~2.7 × 1.0 cm), with internal vascularity—BIRADS 4C. (b) Left breast: Oval high density mass on mammography (white arrow) corresponds to an isoechoic mass with internal vascularity at 2 o’clock position (3.5 x 2.4 cm), matching the palpable concern-BIRADS 4B. (c) Left breast: Spiculated high-density mass on mammography (white arrow) corresponds to an irregular hypoechoic mass with spiculated margins and shadowing at 3 o’clock position (1.5 x 1.4 cm) - BIRADS 4C. (d) The Specimen mammogram of the ultrasound-guided biopsy cores from the right breast at 8 o’clock confirmed the presence of microcalcifications.

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Ultrasound-guided core needle biopsies of the masses in both breasts were performed. The presence of microcalcifications in the right breast biopsy specimen was confirmed by specimen mammography [Figure 2d].

Histopathological evaluation revealed ductal carcinoma in situ (DCIS), intermediate grade, estrogen receptor/progesterone receptor (ER/PR) positive, and human epidermal growth factor receptor 2 (HER2)-negative in the right breast [Figure 3]. In the left breast, the 2 o’clock mass was encapsulated papillary carcinoma [Figure 4], while the 3 o’clock spiculated mass was invasive lobular carcinoma (ILC), grade 2, ER/PR positive, and HER2-negative [Figure 5].

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Figure 3: Histopathology of right breast mass at 8 o’clock position— Ductal carcinoma in situ with comedo pattern—Hematoxylin and Eosin 100X.

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Figure 4: Histopathology of left breast lesion at 2 o’clock position-Encapsulated papillary carcinoma with foci of microinvasion (black arrow) - HE 400X. H and E: Hematoxylin and Eosin

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Figure 5: Histopathology of left breast mass at 3 o’clock position— singly scattered monomorphic cells with single-file pattern and cords of invasive lobular carcinoma—Hematoxylin and Eosin 400X.

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The patient underwent bilateral mastectomy with sentinel lymph node biopsies, which were negative for metastasis. Given the localized disease, favorable receptor status, and absence of nodal or systemic spread, surgery was pursued without neoadjuvant chemotherapy.

DISCUSSION

SBBC is rare, occurring in 1%–2.6% of breast cancer cases. It refers to the development of cancer in both breasts, diagnosed simultaneously or within 3–6 months,^[1,2] and poses unique clinical and prognostic challenges. SBBC typically shares the same histology as the index tumor,^[2] but this case presents three distinct histologic types.

Risk factors for bilateral breast cancer include younger age, lobular histology, and family history.^[3] SBBC is typically detected using imaging modalities such as mammography, ultrasound, contrast-enhanced mammography, magnetic resonance imaging (MRI), and positron emission tomography– computed tomography (PET-CT).^[1]

Breast cancer histopathology highlights tumor heterogeneity. Invasive ductal carcinoma of no special type is the most common (40%–75%). It typically appears as a high-density, spiculated mass on mammography, hypoechoic and irregular on ultrasound, and iso- to hypointense with rapid washout on MRI.^[1]

ILC typically shows spiculated or indistinct margins on mammography and a hypoechoic, irregular mass with shadowing on ultrasound. MRI aids in assessing size, multifocality, and bilateral disease.^[4]

Papillary carcinoma usually appears as a circumscribed, round to lobulated mass on mammography, sometimes with microcalcifications. Ultrasound shows solid or mixed solid-cystic circumscribed masses.^[5] In this case, the lesion was circumscribed and isoechoic.

There are no standardized guidelines for managing SBBC; treatment is typically guided by the tumor with the highest-risk features (e.g., hormone receptor status, HER2, size, grade, and lymphovascular invasion).^[1–3,6,7]

In this case, distinct imaging features prompted biopsy of all three masses, revealing histologic heterogeneity—crucial for individualized treatment planning. Radiologists play a key role in identifying target lesions for biopsy.

The patient underwent bilateral mastectomy with sentinel lymph node biopsies (negative).

Neoadjuvant therapy, though mainly used for locally advanced tumors, is increasingly applied in early-stage disease to assess treatment response.^[6] In this case, localized tumors, favorable receptor status, and absence of nodal or systemic dissemination led to surgery without neoadjuvant therapy. Had any tumor been triple-negative or HER2-positive, neoadjuvant chemotherapy might have been indicated.^[8] This underscores the value of biopsying multiple lesions to identify histologic subtypes that guide therapy. With no benefit expected from downstaging, immediate surgery was appropriate, emphasizing the need for a tailored approach in this case of early-stage SBBC with different histologies.

CONCLUSION

Early detection and assessment of both breasts for any masses with suspicious features—using various imaging modalities and appropriately targeted core biopsy—are crucial for ensuring adequate and appropriate management of bilateral breast cancer. This case underscores the importance of imaging-pathology concordance in distinguishing independent primaries and guiding individualized treatment.