Acantholytic anaplastic Paget's disease.

Classic Paget's disease (PD) can be diagnosed relatively easily by histopathologic examination. 'Anaplastic' variant of this disease is a less-recognized subset that may pose as a diagnostic challenge and pitfall. We describe two cases who presented with scaly erythematous plaques on their nipple/areola. In the first patient, there was no palpable mass and imaging studies were negative. The second case presented with a lesion 5 years after a lumpectomy. Initial shave biopsies revealed histopathologic changes indistinguishable from Bowen's disease with no readily identifiable classic Paget's cells, associated with prominent superficial acantholysis. The neoplastic cells were negative for mucin, GCDFP-15, negative/minimally positive for CEA and strongly positive for CK7 markers. A high-grade ductal carcinoma in situ in the underlying breast was ultimately found in both cases. Anaplastic PD is a rare variant of this disease that histologically mimics Bowen's disease with an associated prominent superficial acantholysis. There is mucin, CEA and GCDFP-15 negativity with positive CK7 reaction. A high index of suspicion along with a complete immunohistochemical panel should be considered in evaluating any Bowenoid neoplasm of the breast skin, particularly in superficial skin shave biopsies along with negative imaging studies and no palpable mass clinically.