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Metaplastic Breast Cancer: Clinical and Prognostic Features

Nidhi Navaratna, BA1, Lihua Qu, MAS, MD2, Mariam Aoun, MD3, Nitya Batra, MD3, Mohammad M Chisti MD3

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1Oakland University William Beaumont School of Medicine, Rochester, MI; 2Corewell Health Research Institute, Royal Oak, MI, 2Corewell Health William Beaumont University Hospital, Royal Oak, MI

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Introduction

  • Metaplastic breast cancer (MpBC) is a rare and aggressive malignancy

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  • MpBC is characterized by the differentiation of neoplastic epithelium into epithelial and mesenchymal components

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  • Carries a poorer prognosis than invasive ductal carcinoma

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Pathology of a MpBC tumor demonstrating differentiation of the neoplastic epithelium into mesenchymal elements1.

Aims and Objectives

  • Collect and analyze demographics, tumor characteristics, staging, metastasis data, hormone receptor status, molecular data, and survival outcomes from electronic medical records of patients diagnosed with metaplastic breast cancer and non-metaplastic, triple-negative breast cancer.

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  • Compare clinical presentation, metastatic patterns, and overall survival between MpBC and non-metaplastic triple-negative breast cancer.

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  • Evaluate the association between hormone receptor status and PD-L1 expression with overall survival.

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Methods

Results

Fig 1a, 1b. Racial and staging distribution of MpBC patients at diagnosis

Fig 2. MpBC tumors demonstrate histopathological heterogeneity

Fig 3. Metastasis was more frequently observed in MpBC cases compared to TNBC cases, commonly affecting the lungs, bones, liver, and brain.

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Results Cont.

Fig 4. Frequently encountered mutations in MpBC included BRCA, KIT, c- MYC, and p53; PD-L1 expression was detected in 8.1% (n=15), and triple-negative status in 24% (n=45) of MpBC cases.

Fig 5a. Overall survival probability for patients with MpBC based on differential expression of estrogen, progesterone, and HER2 receptors.

Fig 5b. Overall survival probability for patients with MpBC based on PD-L1 tumor expression.

Conclusions

  • Metaplastic breast cancer (MpBC) exhibits significant histopathologic and molecular heterogeneity.

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  • MpBC had higher rates of metastasis than non-metaplastic breast cancer, but without a significant difference in overall survival.

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  • Histopathologic subtype did not significantly influence overall survival.

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  • Triple-negative status was associated with decreased overall survival, and PD-L1 negativity was associated with increased mortality.�

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References

  • Thapa B, Arobelidze S, Clark BA, Xuefei J, Daw H, Cheng YC, Patel M, Spiro TP, Haddad A. Metaplastic Breast Cancer: Characteristics and Survival Outcomes. Cureus. 2022 Aug 29;14(8):e28551. doi: 10.7759/cureus.28551. PMID: 36185859; PMCID: PMC9517584.

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  • McMullen ER, Zoumberos NA, Kleer CG. Metaplastic Breast Carcinoma: Update on Histopathology and Molecular Alterations. Arch Pathol Lab Med. 2019 Dec;143(12):1492-1496. doi: 10.5858/arpa.2019-0396-RA. PMID: 31765246.