Invasive lobular carcinoma with papillary features: A newly described variant that poses a difficult histologic differential diagnosis.

Recently, a new variant of ILC with papillary architecture has been described, which may mimic solid and encapsulated papillary carcinomas of the breast. We report the fifth case of ILC with a solid papillary-like growth pattern, which was initially misdiagnosed as an encapsulated papillary carcinoma. Subtle discohesion in the tumor cells, coupled with the presence of classic invasive lobular carcinoma infiltrating beyond the capsule of the papillary tumor, prompted evaluation with E-cadherin, confirming the diagnosis. We review the histologic differential diagnosis and stress the importance of correct classification to ensure appropriate management for patients.