Unintentional weight loss
This patient's clinical presentation is consistent with a diagnosis of metastatic invasive lobular carcinoma, with nodal involvement.
Breast cancer is one of the most frequently diagnosed cancers worldwide. In Western countries, 1 in 8 women will be diagnosed with breast cancer at some point in their lives. Various histologic subtypes with specific clinical characteristics exist. Invasive lobular carcinoma (ILC) is the second most common subtype, accounting for an estimated 10%-15% of breast cancers. Over the past two decades, a significant increase has been observed in the incidence of ILC, particularly among postmenopausal women. Improved diagnostic techniques and the use of hormone replacement therapy may account for this increased incidence. White women have the highest incidence of ILC; however, compared with White women and women of other races, Black women experience the worst 5-year overall survival from ILC.
ILC arises in the mammary ducts (lobules) of the breast. Women with ILC are typically slightly older than women with invasive breast cancer of no special type at diagnosis (mean age 63.4 vs 59.5 years, respectively). Risk factors for ILC may include early menarche, use of progesterone-based hormone replacement therapy, late age at first live birth, and alcohol consumption.
In most cases, ILC does not form a discrete palpable mass until it has reached an advanced stage, making it more difficult to detect through physical examination or imaging. Patients often present with a large tumor and with nodal involvement. A slight thickening of the nipple, an exudative scab on the skin, or other changes in the skin, such as flushing or swelling, may be seen in patients presenting with advanced disease. Additionally, ILC tumors are often bilateral and multifocal.
ILC is predominantly a histopathologic diagnosis based on standard hematoxylin and eosin staining. Histologically, ILC is characterized by a proliferation of small cells that lack cohesion. These cells are often dispersed individually through a fibrous connective tissue; alternatively, they may be organized in single-file linear cords invading the stroma. A concentric pattern around normal ducts is often seen in the infiltrating cords. There is usually little host reaction of the background architecture. Round or notched ovoid nuclei are seen in the neoplastic cells, along with a thin rim of cytoplasm. Occasionally, an intracytoplasmic lumen is present and may harbor a central mucoid inclusion. Very few or no mitoses are seen.
Several variants of ILC exist, all of which lack cell-to-cell cohesion. These include:
• Solid type
• Pleomorphic lobular carcinoma
• Tubulo-lobular variant
• Alveolar variant
• Mixed type
Complete loss of E-cadherin expression occurs in most ILCs, which can help to differentiate it from invasive ductal cancers or ductal carcinomas in situ. Diffuse cortical thickening without hilar mass effect is often seen in nodal metastases associated with ILC.
Most classic ILCs are estrogen receptor– and progesterone receptor–positive. Conversely, HER2 overexpression and amplification rarely occurs in ILC.
Late relapses more than 10 years after remission may occur. In addition to frequent bone and liver metastasis, ILC is associated with metastatic spread to unusual sites, including the peritoneum, gastrointestinal tract, urinary tract, leptomeninges, skin, orbit, and ovaries.
Mastectomy is often indicated in ILC. In the neoadjuvant setting, ILC is associated with low pathologic complete response rates. Endocrine therapy in the neoadjuvant setting is an emerging approach for some patients with ILC. According to 2022 National Comprehensive Cancer Network guidelines, adjuvant chemotherapy followed by endocrine therapy or endocrine therapy alone should be considered for pre- and postmenopausal patients with ILC.
Avan J. Armaghani, MD, Assistant Member, Department of Breast Oncology, Moffitt Cancer Center, University of South Florida, Tampa, FL.
Avan J. Armaghani, MD, has disclosed no relevant financial relationships.
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