Imaging patterns and diagnostic challenges in metastatic invasive lobular carcinoma

Area of Science:

• Oncology
• Radiology
• Nuclear Medicine

Background:

• Invasive lobular carcinoma (ILC) is the second most common breast cancer subtype, characterized by diffuse infiltration due to E-cadherin loss.
• ILC exhibits unique metastatic patterns, often involving the peritoneum, gastrointestinal tract, ovaries, and leptomeninges, with infiltrative lesions complicating diagnosis.
• The heterogeneity of ILC, including aggressive variants like pleomorphic ILC, necessitates specialized diagnostic approaches.

Purpose of the Study:

• To provide a comprehensive review of metastatic ILC from radiology and nuclear medicine perspectives.
• To highlight diagnostic challenges and key imaging features of ILC metastases.
• To emphasize the need for advanced imaging strategies beyond standard methods for accurate detection and staging.

Main Methods:

• Review of imaging findings in metastatic ILC, integrating radiology and nuclear medicine.
• Emphasis on whole-body diffusion-weighted MRI (WB-DWI) for detecting infiltrative lesions.
• Discussion of advanced PET/CT tracers, including 18F-fluoroestradiol (FES) and fibroblast activation protein inhibitor (FAPI) imaging, due to ILC's variable 18F-FDG avidity.

Main Results:

• ILC's diffuse infiltration and infiltrative metastases often mimic benign conditions, leading to diagnostic pitfalls.
• Standard 18F-FDG PET/CT may show low or heterogeneous uptake in ILC, potentially missing metastatic disease.
• WB-DWI, FES-PET/CT, and FAPI-PET/CT offer improved detection of ILC metastases.

Conclusions:

• The distinctive metastatic behavior and imaging characteristics of ILC can lead to delayed diagnosis.
• Radiologists and nuclear medicine physicians require increased awareness of ILC's specific patterns.
• Dedicated, advanced imaging approaches are crucial for reducing missed or late diagnoses of metastatic ILC.