A difficult-to-diagnose fibromatosis-like metaplastic carcinoma of the breast: a case report

Abstract

Background: Fibromatosis-like metaplastic carcinoma (FLMCa), classified as a metaplastic carcinoma of the breast, is a very rare type of metaplastic carcinoma. We report a case of FLMCa that was difficult to diagnose.

Case presentation: The patient was a 56-year-old postmenopausal woman who presented with a left-sided breast mass. A 1.3-cm irregular mass was found in the lower outer quadrant of the left breast on breast ultrasonography. She underwent core needle biopsy and vacuum-assisted biopsy, but the pathological findings only revealed inflammatory cell infiltration and a high level of fibrosis, with no malignant findings. At 3 months follow-up, she underwent a repeat breast ultrasonography, which revealed an increase in the size of the mass to 1.8 cm, and a repeat core needle biopsy, which showed a few spindle cells and squamous cells positive for cytokeratin (CK)5/6 and AE1/AE3, leading to the suspicion of FLMCa. Since the amount of tissue was insufficient to establish a definitive diagnosis, she underwent a lumpectomy. We found low-grade and slightly atypical spindle cells and partly atypical spindle cell carcinoma and squamous cell carcinoma. CK5/6 and α-SMA were positive, thus confirming FLMCa. Because the margins on the edge of the nipple side and anterior side were "ink on tumor", she underwent a mastectomy and sentinel lymph node biopsy. After the surgery, she received adjuvant chemotherapy. At 3 years and 8 months of follow-up, no recurrent or metastatic lesions were identified in her body.

Conclusions: FLMCa should be considered in the differential diagnosis when collagenous fibers are proliferating and malignancy is clinically suspected. Immunohistochemical analysis may be helpful in confirming this diagnosis.

Keywords: Breast cancer; Fibromatosis-like metaplastic carcinoma; Metaplastic carcinoma.

Fig. 1

Mammography. In the lower and outer areas of the left breast, a 2-cm micro-lobulated high-density mass was observed (arrows)

Fig. 2

Breast ultrasonography. A 1.3 × 1.0 × 1.1-cm irregular hypoechoic mass with angular margin mass was found in the lower outer quadrant of the left breast

Fig. 3

Magnetic resonance imaging. a A 1.9 × 1.8 × 1.7-cm irregular tumor was observed in the lower, outer quadrant of the left breast, which was well imaged in the early phase. b The tumor was washed out in the late phase

Fig. 4

Immunohistological findings of the biopsy. a Proliferation of fibroblast-like spindle cells was observed (H&E × 100). b Partial agglomeration of squamous cell-like cells with low-grade atypical nuclei was observed (H&E × 100). c CK5/6 were positive in spindle cells (× 100). d AE1/AE3 were positive in squamous cells (arrows × 100). H&E hematoxylin and eosin, CK cytokeratin

Fig. 5

Immunohistological findings of the lumpectomy specimen. a Low-grade and slightly atypical spindle cells and partly atypical spindle cell carcinoma were observed (H&E × 100). b Partly atypical squamous cell carcinoma was observed (H&E × 100). c α-SMA was positive in spindle cells. d CK5/6 were positive in squamous cells. H&E hematoxylin and eosin, SMA smooth muscle actin, CK cytokeratin