Invasive Lobular Carcinomas

Introduction

Hello, my name is Soudabeh Fazeli, from the University of California, San Diego. In this talk, I'm going to discuss invasive lobular carcinomas.

Objectives

• Understand how the pathologic features of invasive lobular carcinomas (ILCs) predict clinical and imaging findings.
• Identify the subtle mammographic findings of ILC.
• Recognize the classic features and pitfalls in ultrasound evaluation of ILC.
• Describe the role of MRI in the evaluation of ILC.

Pathologic Features

Invasive lobular carcinoma is the second most common invasive cancer of the breast. Unfortunately, ILC is notoriously difficult to detect both clinically and on imaging due to its slow-growing and insinuating nature, often resulting in no clinically palpable mass and subtle mammographic and sonographic changes.

• Second most common subtype of invasive breast cancer.
• Accounts for about five to fifteen percent of all invasive breast cancers.
• ILCs are often missed or have delayed diagnoses.
• Incidence has slightly increased over the past two decades.
• ILCs are more common in patients with lobular carcinoma in situ or atypical lobular hyperplasia.

Unique Histopathology

The unique histopathology of ILC, consisting of small, uniform cells that infiltrate around ducts and lobules in a classic single-file pattern, makes them difficult to detect.

• Good prognostic phenotype: low histological grade, hormone receptor positive, HER2 negative.
• Can be highly metastatic due to the infiltrative nature of the cells.
• Low density of tumor cells and lack of desmoplastic stromal reaction.
• Loss of adhesion molecule E-cadherin, responsible for cell-to-cell adhesion.

Mammographic Findings

The most common mammographic manifestation of ILC is a mass with spiculated or indistinct margins. Mammogram sensitivity ranges from 57 to 81 percent.

• ILC can present as asymmetries, focal asymmetry, shrinking breast appearance, rare microcalcifications, and skin and nipple changes.

Ultrasound Findings

Ultrasound has superior sensitivity for ILC detection compared to mammography, with sensitivity as high as 98 percent.

• Most common ultrasound manifestation is a hypoechoic, irregular mass with posterior shadowing.
• ILCs can also present as focal shadowing without a discrete mass.

MRI Findings

MRI is the most accurate imaging modality for evaluating ILC, with sensitivity as high as 95 percent.

• Superior to both mammography and ultrasound for detecting ILC, multifocality, multicentricity, contralateral disease, and estimating tumor size.
• MRI findings often lead to changes in surgical management in up to 50 percent of patients with ILC.

Conclusion

Invasive lobular carcinoma presents unique clinical and imaging challenges due to its infiltrative nature. Comprehensive imaging, including mammography, ultrasound, and MRI, is crucial for accurate detection, characterization, and management of ILC.