E2106. Pleomorphic Lobular Carcinoma In Situ: A High-Risk Breast Lesion
  1. Christine Guerrini; Maine Medical Center; Tufts University School of Medicine
  2. Carrie Anne Orlikowski; Maine Medical Center; Tufts University School of Medicine
  3. Christina Cinelli; Maine Medical Center; Spectrum Healthcare Partners
  4. Elizabeth Pietras; Maine Medical Center; Spectrum Healthcare Partners
Lobular breast carcinomas - those originating from the cells of the breast lobules and terminal ducts - represent the second most common type of primary breast cancer. As with their more common counterpart, ductal carcinomas, a spectrum of non-obligate lobular precursor lesions has been identified. Under this umbrella of lobular carcinoma in situ (LCIS), several histopathologic subtypes exist, including classic, florid, and pleomorphic. This exhibit explores the newly-described pleomorphic subtype, which conveys a higher risk of upgrade to invasive carcinoma and warrants more aggressive treatment. We will explore the pathophysiology of these lesions, review the current treatment recommendations, and review imaging of several recent case examples from our institution.

Educational Goals / Teaching Points
Lobular breast cancer, which derives from lobules and terminal ductal tissue, represents the second most common primary breast malignancy. Lobular carcinoma in-situ (LCIS) is a high-risk proliferative lesion of lobular tissue and a non-obligate precursor to invasive lobular carcinoma. Patients diagnosed with LCIS are more likely to have come from high-risk groups and to have received "high-risk" screening. LCIS may present as calcifications, masses, or non-mass enhancement. There are different subtypes of LCIS, including classic, florid, and pleomorphic. Pleomorphic lobular carcinoma in-situ is a relatively newly-described subtype, which conveys a higher risk of upgrade to invasive cancer than classic LCIS. Due to its higher invasive potential, more aggressive treatment is recommended for pleomorphic LCIS than the classical subtype.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The distinction between LCIS subtypes is a histopathologic diagnosis, and no specific imaging findings have been identified yet to differentiate these lesions. Thus, we will review cases of common mammographic and ultrasound findings that warrant further investigation if identified on screening or diagnostic examinations. We will also illustrate the limitations of mammography and ultrasound in identifying the full extent of disease.

LCIS is a non-obligate precursor lesion to invasive lobular carcinoma, with several identified histologic subtypes. One newly-described subtype, pleomorphic LCIS, conveys a high risk of upgrade to invasive cancer, and therefore warrants aggressive treatment early in its course. Although the radiological appearance of pleomorphic LCIS itself is nonspecific, it is important for breast imagers to be aware and able to identify high-risk lesions so that appropriate treatment can be pursued.