乳腺低悪性度（線維腫症様）紡錘細胞癌の1例

A case of low grade（fibromatosis-like）spindle cell carcinoma of the breast

乳腺の低悪性度（線維腫症様）紡錘細胞癌は，紡錘細胞癌の一亜型であり，WHO分類（第4版）で化生癌の項目に入るまれな組織型の乳腺腫瘍である。今回我々は，画像的に悪性腫瘍が疑われたにもかかわらず，針生検では癌細胞を認めず，腫瘍摘出生検後に低悪性度（線維腫症様）紡錘細胞癌と診断された症例を経験した。

We report a case of low grade（fibromatosis-like）spindle cell carcinoma of the breast. Mammography showed a dense mass in the left breast. Ultrasonography revealed a well-circumscribed hypoechoic mass. MRI showed a solid mass with an early peripheral enhancement and a central nonenhancing area. Although these findings suggested breast carcinoma, the core needle biopsy showed no malignancy. The histopathological examination following the tumor excision diagnosed low grade（fibromatosis-like）spindle cell carcinoma, which is a rare breast tumor categorized as a subset of metaplastic carcinoma.