Pleomorphic Lobular Carcinoma In Situ

• Pleomorphic Lobular Carcinoma In Situ (PLCIS) is a rare, non-invasive breast lesion with distinct cellular features.
• It is typically asymptomatic and often discovered incidentally during mammography or biopsy for other reasons.
• Diagnosis relies on microscopic examination by a pathologist, identifying characteristic pleomorphic cells.
• Treatment primarily involves surgical excision to achieve clear margins.
• PLCIS carries a higher risk of progression to invasive breast cancer compared to classic LCIS, necessitating vigilant follow-up.

What is Pleomorphic Lobular Carcinoma In Situ (PLCIS)?

Pleomorphic Lobular Carcinoma In Situ (PLCIS) is a specific type of non-invasive breast lesion where abnormal cells are confined to the lobules and ducts of the breast, without breaking through the basement membrane. Unlike classic lobular carcinoma in situ (LCIS), PLCIS is characterized by cells that exhibit significant nuclear pleomorphism (variation in size and shape), prominent nucleoli, and often a higher mitotic rate. This cellular atypia gives it a more aggressive appearance under the microscope, placing it in a category of high-risk proliferative lesions.

PLCIS is considered a less common variant, accounting for a small percentage of all LCIS diagnoses. While exact prevalence varies, some studies suggest it represents approximately 1-2% of all lobular in situ lesions. Its recognition is crucial because it is associated with a higher likelihood of concurrent or subsequent invasive carcinoma compared to classic LCIS, necessitating a different management approach. It is classified as a non-obligate precursor lesion, meaning not all cases will progress to invasive cancer, but the risk is elevated.

Symptoms and Diagnosis of Pleomorphic Lobular Carcinoma In Situ

There are typically no specific pleomorphic lobular carcinoma in situ symptoms that a patient would notice. PLCIS does not usually present as a palpable lump or cause pain. Instead, it is most often an incidental finding during a breast biopsy performed for other reasons, such as suspicious microcalcifications detected on a mammogram or an abnormal finding on an MRI. These microcalcifications, while not exclusive to PLCIS, can sometimes be the only radiological clue.

The definitive diagnosis of PLCIS relies on microscopic examination of breast tissue by a pathologist. Key diagnostic features include:

• Cells with marked nuclear pleomorphism (variability in nuclear size and shape).
• Prominent nucleoli within the cell nuclei.
• Intralobular and intraductal proliferation of these atypical cells.
• Often, the cells show loss of E-cadherin expression, a characteristic feature of lobular differentiation, which is confirmed through immunohistochemistry (IHC) staining.

Due to its varied cellular appearance, distinguishing PLCIS from other breast lesions, including ductal carcinoma in situ (DCIS) or even invasive carcinoma, can be challenging and requires experienced pathological review.

Treatment and Prognosis for Pleomorphic Lobular Carcinoma In Situ

The primary pleomorphic lobular carcinoma in situ treatment involves surgical excision to ensure complete removal of the lesion with clear margins. This typically means a lumpectomy, where the abnormal tissue and a surrounding rim of healthy tissue are removed. The goal is to eliminate the lesion and reduce the risk of progression to invasive cancer. Unlike invasive carcinoma, sentinel lymph node biopsy is generally not indicated for PLCIS unless there is concurrent evidence or strong suspicion of invasion.

Following surgical excision, ongoing surveillance is a critical component of management. This usually includes regular clinical breast exams and annual mammograms. In some cases, depending on individual risk factors and the extent of the lesion, risk-reducing medications such as tamoxifen or aromatase inhibitors may be considered, similar to their use in other high-risk breast lesions. The decision for adjuvant therapy is highly individualized and made in consultation with an oncologist.

The pleomorphic lobular carcinoma in situ prognosis is generally favorable when the lesion is completely excised. However, it is important to understand that PLCIS is associated with a significantly higher risk of subsequent invasive breast cancer compared to classic LCIS. Studies indicate that the risk of developing invasive breast cancer in either breast after a PLCIS diagnosis can range from 10% to 30% over 10-15 years, highlighting the importance of vigilant follow-up and adherence to screening recommendations. This elevated risk underscores the need for careful monitoring and personalized management strategies to detect any potential progression early.