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Although apocrine carcinoma is a distinct histologic entity, there is no immunohistochemical marker to confirm apocrine differentiation with high sensitivity and specificity, and its differential cytologic characteristics are still not fully clarified. Despite the foamy cytoplasm of some apocrine carcinomas and the existence of lipid in the normal apocrine gland, intracytoplasmic lipid in apocrine carcinomas has not been fully explored. By using immunohistochemistry for adipophilin, which is a specific marker of lipid accumulation that can be applied to paraffin sections, we examined intracytoplasmic lipid in apocrine carcinomas. Twenty-four of 26 (92%) apocrine carcinomas and 38 of 116 (33%) nonapocrine carcinomas contained intracytoplasmic lipid. The frequency of adipophilin-positive cases was significantly higher in apocrine carcinomas compared with nonapocrine carcinomas (P90% of the tumor cells; thus, the criteria for lipid-rich carcinoma was not fulfilled. However, the immunohistochemical study suggests that lipid-rich carcinomas are closely related to apocrine carcinomas.
Moritani et al. (Fri,) studied this question.