GS16 - Fibromatosis-like metaplastic carcinoma of the breast

Primary Presenter(s)

DJ

Daaniya Jamal, OMS-IV

PCOM South Georgia
Moultrie, Georgia, United States

Co-Presenter(s)

SS

Shivani Sookchand, OMS-IV

PCOM South Georgia
Moultrie, Georgia, United States
PP

Pavan Patel, OMS-IV

Philadelphia College of Osteopathic Medicine
Moultrie, Georgia, United States

Introduction/Purpose:

Introduction: Fibromatosis-like metaplastic carcinoma of the breast is a very rare, but aggressive tumor of the breast. The reported incidence of FLMC is less than 0.5 - 5% of all invasive breast cancer. Clinically, fibromatosis often mimics carcinoma of the breast, sometimes presenting with skin dimpling. Diagnosing FLMC is challenging due to its unconventional differentiation of connective tissue with resemblance to low-grade spindle cell tumors. Extra-abdominal desmoid tumors make up less than 3% of all desmoid tumors, with breast malignancies representing 0.2% of all primary tumors.

Methods or Case Description: The patient is an 80-year-old female patient diagnosed with Fibromatosis-like metaplastic breast carcinoma. The patient had a diagnostic mammogram that revealed a persistent asymmetry and enlarging heterogeneous mass of the left breast at the 5 o’clock position, now measuring 14mm x 8mm with vascular calcifications. With an impression of BIRADS Category 4, a follow-up ultrasound-guided core needle biopsy was performed. Pathology of the specimen obtained via ultrasound-guided core needle biopsy of the suspicious lesion was significant for Fibromatosis-like metaplastic carcinoma of the left breast. She was referred to general surgery for further evaluation and management of the fibromatosis.

Outcomes: The patient underwent a partial mastectomy with a tan-white fibrous lesion 1.2 x 1.0 x 0.6 cm in size with 0.2 cm clear margins and a left axillary sentinel lymph node biopsy that measured 0.7 cm in the greatest dimension. The excision of the mass was consistent with a diagnosis of invasive fibromatosis-like metaplastic carcinoma with no evidence of metastasis to the sentinel lymph node. The pathology stains were negative for E-cadherin and P-63 negative, and focally positive for Cytokeratin 5/6.

Conclusion: Fibromatosis-like metaplastic carcinoma (FLMC) is a rare, variant of low-grade metaplastic carcinoma histologically classified with the presence of “bland spindle cells resembling fibromatosis within abundant stromal collagen.” The presence of spindle cells in breast carcinoma can be incorrectly diagnosed as fasciitis, fibromatosis, or myofibroblastic tumors. FLMC’s expected immunochemical profile is often grouped with other metaplastic carcinomas of the breast, according to WHO guidelines. Immunochemical staining and diagnosis for metaplastic breast cancers are not standardized with various small studies reporting that most MBC (metaplastic breast cancers) are triple-negative (ER-, PR-, HER2-) and CD 34 negative. Other antibodies such as CK 5/6 are positive in the majority of MBC, with positivity varying from 86.9% to 69.6% in a comparison of 23 cases. Antibody cytokeratin (AE1/AE3) was found to be positive in 95.6% of metaplastic breast cancers and p63 positive 91.3 % of the time in the same study.

On physical examination, the carcinoma is primarily detected as a solitary palpable mass that tends to affect the breasts unilaterally. Over the past couple of years, the incidence of FLMC has been increasing with imaging modalities such as mammography and ultrasounds in females >50 years of age; however, a high clinical index of suspicion is still needed to diagnose FLMC due to the variability with immunochemical markers, nonspecific histology, and inconsistencies it’s the appearance on recommended imaging modalities.