Which statement about the comparison between invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) is accurate?

• A. IDC commonly displays desmoplastic stroma with ductal invasion
• B. ILC characteristically forms single-file cells with minimal desmoplasia
• C. IDC never metastasizes
• D. ILC is always triple-negative

Answer: (B)

Invasive lobular carcinoma tends to invade in a single-file or Indian-file pattern of small, uniform cells, with only minimal desmoplastic (fibrous) stromal reaction. This discohesive growth is driven by loss of E-cadherin, a cell–cell adhesion protein, which makes the cells spread in linear strands rather than forming cohesive nests. That combination—single-file infiltration and little surrounding fibrous response—is the hallmark that sets lobular carcinoma apart from the more cohesive, duct-forming invasive ductal carcinoma, which usually elicits a more pronounced desmoplastic stroma.

So the statement describing lobular carcinoma as characteristically forming single-file cells with minimal desmoplasia accurately captures its distinctive histology. In contrast, invasive ductal carcinoma commonly shows duct-like structures or cohesive tumor nests with a more substantial desmoplastic reaction. Additionally, lobular carcinoma is not defined by being triple-negative; it often expresses hormone receptors (ER/PR) and is not inherently limited to a single receptor status. And IDC can metastasize, so saying it never does is incorrect.