2018 Volume 67 Issue 5 Pages 809-816
Squamous cell carcinoma (SqCC) of the breast is rare and generally aggressive associated with rapid progression. We report a case of SqCC of the breast with a favorable prognosis. The patient was a woman in her 60s. The breast dynamic magnetic resonance imaging (MRI) showed a mass as a “delayed rim enhancement”, on which fine-needle aspiration cytology (FNAC) was performed. The FNAC smear was cellular and contained necrotic debris, lymphocytic inflammatory cells, and a few mesenchymal fragments. Although most of the cells appeared as clusters, some appeared as single keratinizing cells. A large cell (70-μm-diameter) with a giant nucleus and a thick cytoplasm was protruded from periphery of a large cluster consisting of tumor cells of various sizes. Immunocytochemical staining of small clusters distinguished between the clusters consisting only of p40-positive cells and those with both p40-positive and p40-negative cells. In large clusters consisting of streaming arrangements of uniform tumor cells, the positivity for p40 showed a biased distribution to one side. Histopathologically, she was diagnosed as having SqCC arising in the breast. Transitional features from adenocarcinoma (AC) to SqCC were sporadically observed. Immunohistochemically, ER/PR/HER2 was negative. The Ki-67 positivity rate was 55%. SqCC of the breast showed distinctive cytological findings such as keratinizing cells with marked atypia and cell clusters containing portions transitioning from AC to SqCC. We considered that FNAC as an investigation method for small breast lesions is useful for the early diagnosis of SqCC and therapeutic planning.
