Variants of squamous cell carcinoma of the breast: Should they be a unique entity?

Committee/Faculty

Presenting Author(s)

SF

Sayeh Fattahi

BS, BA
Alix School of Medicine, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.

Co-Author(s)

EJ

Elizabeth B. Jeans

MD
Department of Radiation Oncology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
MS

Malvika H. Solanki

MBBS, PhD
Department of Anatomic Pathology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
KG

Kimberly R. Gergelis

MD
Department of Radiation Oncology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
DC

Danielle A. Cunningham, MD

MD
Department of Radiation Oncology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
AA

Arslan Afzal

MBBS
Department of Radiation Oncology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
IZ

Isabella Zaniletti

PhD
Department of Clinical Trials and Biostatistics, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
MV

Molly M. Voss

MS
Department of Clinical Trials and Biostatistics, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
TS

Tiffany M. Sae Kho

MD
Department of Diagnostic Radiology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
KG

Katrina N. Glazebrook

MB, ChB
Department of Diagnostic Radiology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
DS

Dean A. Shumway

MD
Department of Radiation Oncology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
RM

Robert W. Mutter

MD
Department of Radiation Oncology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.
KC

Kimberly S. Corbin

MD
Department of Radiation Oncology, Mayo Clinic
Rochester, Minnesota, United States

Disclosure: Disclosure information not submitted.

Purpose: Variants of squamous cell breast cancer may represent an aggressive form of subtype, which is rarely studied independently and may present a unique therapeutic challenge. We report our institution’s experience with treating these patients.

Methodology: All patients with breast cancer treated between 1972 and 2018 with squamous features or differentiation were identified. After pathologic confirmation of the diagnosis, available patient and treatment characteristics were collected. Disease outcomes were calculated based upon patient factors.

Results: 113 patients were identified meeting the criteria above. Patients were classified into 5 groups based on histopathology: metaplastic carcinoma with squamous features/differentiation (78 patients), invasive ductal/lobular/mammary carcinoma with squamous features/differentiation (24 patients), pure invasive squamous cell carcinoma (2 patients), low grade adenosquamous carcinoma (7 patients), and phyllodes tumors with squamous features/differentiation (2 patients). Median age was 58.9 years. 75 patients (66.3%) had poorly differentiated carcinoma. 37 patients (32.7%) were hormone receptor positive, 11 (9.7%) were HER2+, and 62 (54.9%) were triple negative. 57 (50%) underwent mastectomy (median tumor size 3.4 cm) and 55 (49%) underwent breast conserving surgery (median tumor size 2.0 cm). 1 patient did not undergo any surgery. 58 (51.3%) received radiation therapy to a median of 50 Gy and 66 (58.4%) received chemotherapy.

Median follow up was 2.7 years overall and 3.6 years for surviving patients. At 5 years, overall survival was 68.9% for the entire cohort, 60.7% for patients who underwent mastectomy, and 82.1% for patients who underwent breast conserving surgery (p = 0.07). Progression free survival was 58.3% for the entire cohort, 50.2% for patients who underwent mastectomy, and 70.7% for patients who underwent breast conserving surgery (p = 0.11). Freedom from local recurrence was 83.4%, freedom from regional recurrence was 87.2%, and freedom from distant recurrence was 68.9% for the entire cohort; 83.8%, 87.7%, and 62.7% for patients who underwent mastectomy; and 85.9%, 89.9%, and 79.5% for patients who underwent breast conserving surgery. Small numbers preclude sub-group analysis, though we note that all recurrence rates were highest in the metaplastic carcinoma group.

Conclusions: Breast cancer with squamous features is a rarer form of breast cancer with unclear outcomes. Patients appear younger with a higher portion of hormone receptor negativity. Patients who underwent breast conserving surgery trended toward better outcomes than those who underwent mastectomy, possibly due to more advanced disease (45% T2 or higher in breast conserving surgery patients vs. 86% T2 or higher in mastectomy patients). There was no difference in locoregional recurrence between mastectomy and breast conserving surgery patients, supporting lumpectomy where appropriate. Distant metastasis was the most frequent site of recurrence. Further investigation is warranted to determine trends in the context of advancements and personalization in treatment paradigms.

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