Fig. 2: Distinctive histologic features of invasive lobular carcinoma with extracellular mucin (ILCEM). | Modern Pathology

Fig. 2: Distinctive histologic features of invasive lobular carcinoma with extracellular mucin (ILCEM).

From: Invasive lobular carcinoma with extracellular mucin (ILCEM): clinicopathologic and molecular characterization of a rare entity

Fig. 2

(a–d) Case 14. ILCEM in which the mucinous component consists of solid cellular nodules of signet ring cells in extracellular mucin (a, b). The tumor also contains ILC with a conventional growth pattern and pleomorphic LCIS (c, d). (e, f) Case 6. ILCEM is composed of rhabdoid pleomorphic apocrine tumor cells in an unusual discohesive alveolar growth pattern. (g, h) Case 8. Expansile nodules of mucin-producing signet ring cell LCIS transitioning to ILCEM. The signet ring cell LCIS is associated with abundant extracellular mucin and massive acinar expansion, with foci of rupture and contiguous pools of extravasated mucinous lobular carcinoma, and with foci of interspersed irregular pools of frankly invasive mucinous lobular carcinoma (g). A p63 immunohistochemical stain demonstrates the presence of a myoepithelial cell layer at the periphery of LCIS (short arrow) and the loss of this layer at the edge of the contiguous pool of extravasated tumor-containing mucin (long arrow) (h). The signet ring cell LCIS in this case represents the only example of mucin-producing LCIS.

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