A case of invasive micropapillary carcinoma of the male breast

Background: We report a case of invasive micropapillary carcinoma (IMPC) of the male breast. Case: A 73-year-old man seen for a painless hard 7 mm mass lateral to the right nipple was found in fine-needle aspiration cytology to have many clusters of small to medium sized cancer cells characterized by a relatively clear cytological background and marked protrusion of the cytoplasm at the periphery of clusters (lumenforming and solid types ; L and S types). Cell clusters with fibrovascular stalks were noted at many points (papillary subtype; P subtype). Histologically, the lesion showed the typical features of invasive micropapillary carcinoma (IMPC) separated by a mesh-like stroma. A papillary architecture (P subtype) was noted histologically, endorsing cytological findings. Observation of serial sections revealed continuity of the L and S types IMPC and P subtype IMPC to the papillotubular carcinoma with small fibrovascular stalks. Conclusion: Based on these findings, we propose adding the “P type”(papillary subtype), resembling papillotubular carcinoma, to the conventional classification of IMPC.