Fig. 1: Histologic features of invasive lobular carcinoma with extracellular mucin (ILCEM).

(a, b) Case 9. The ILCEM is present as tumor cells suspended in small pools of mucin associated with a classic component. (c–h) Case 2. The ILCEM is a mixture of solid and classic components. There are solid cellular tumor nodules with scant extracellular mucin (c) and large pools of mucin (c, d), both consisting of predominantly pleomorphic signet ring cells (e). Classic ILC is also present (f). Immunohistochemical stains show loss of E-cadherin expression (g) and aberrant cytoplasmic p120 expression (h) in tumor cells.