7 Metaplastic Breast Cancer: A Retrospective Chart Review of Clinical Features

7 Metaplastic Breast Cancer: A Retrospective Chart Review of Clinical Features

Background

Metaplastic breast cancer (MpBC) is a rare and aggressive malignancy characterized by the differentiation of the neoplastic epithelium into epithelial and mesenchymal elements. MpBC carries a poorer prognosis compared with invasive ductal carcinoma, likely due to its histopathological and molecular heterogeneity and lack of specific treatment protocols. The rarity and complexity of MpBC calls for further inquiry into its clinical characteristics.

Materials and Methods

An institutional review board-approved retrospective chart review was conducted on patients diagnosed with metaplastic breast cancer and non-metaplastic, triple-negative breast cancer (TNBC) from January 2000 to August 2023 at our institution. Pathology reports of breast tissue were reviewed to characterize MpBC tumors into distinct histopathological groups. The study included 186 patients with metaplastic breast cancer (MpBC) and 76 patients with non-metaplastic TNBC.

Results

The median age of metaplastic breast cancer diagnosis was 62 years, with stage distribution as follows: stage I (34%, n = 13), stage II (18%, n = 7), stage III (13%, n = 5), and stage IV (26%, n = 10). The racial distribution among patients with MpBC was predominantly White (126 patients, 70.0%), followed by Black (47 patients, 26.1%).

Histopathological analysis of metaplastic breast cancer tumors showed tumor differentiation into the following histological subtypes: 44.62% (n = 58) with squamous features, 26.15% (n = 34) with spindle cell features, 3.85% (n = 5) with adenosquamous features, 13.85% (n = 18) with chondroid features, 1.54% (n = 2) with osseous features, and 10.00% (n = 13) with mixed epithelial/mesenchymal features (Figure). No significant differences in overall survival were noted between histological subtypes.

Figure. Histological Features of Metaplastic Breast Cancer Tumors (N=130)

Mutations were found in BRCA (9%, n = 17), KIT (2.7%, n = 5), c-MYC (2.2%, n = 4), and p53 (1.6%, n = 3), with PD-L1 expression detected in 8.1% (n = 15), and triple-negative status identified in 24% (n = 45) of patients with MpBC. Metastases were noted in 83.9% of MpBC cases (n = 156), compared with 61.8% of TNBC cases (n = 47), most commonly affecting the lungs, bones, liver, and brain. Treatment strategies included anthracycline-based chemotherapy and combination therapy with anthracycline-based regimens and immunotherapy.

Conclusion

This study summarizes the clinical characteristics of MpBC, highlighting its histological heterogeneity and the potential role of pathological and molecular profiling in guiding research. Further studies are required to build upon these results, with the goal of improving patient outcomes for this rare malignancy.