Objectives: We tried to describe cellular immune response (tertiary lymphoid structures (TLSs), lymphoid aggregates, tumor infiltrating lymphocytes (TILs)) in neoplastic microenvironment of ductal carcinoma in situ (DCIS) with or without associated microinvasion.
Methods: The histopathologic parameters of 177 DCIS and 27 DCIS with microinvasion were evaluated. We determined number of ducts involved by DCIS, and calculated percentage of these ducts surrounded by TLSs. TILs were quantitated in 27 microinvasive cases.
Results: Tumors having higher percentage of DCIS ducts associated with TLSs had higher incidence of microinvasion (P < .001). Percentage of DCIS ducts involved by TLSs was also higher in hormone receptor (HR)−/human epidermal growth factor receptor 2 (HER2)+ and TNBC subtypes of DCIS than in HR+/HER2− and HR+/HER2+ subtypes (38.04 ± 25.8%, 32.6 ± 32.4%, 2.5 ± 7.3% and 17.4 ± 23.3%, respectively, P < .001). In DCIS without microinvasion, HR+/HER2− subtype predominated (P < .001). In microinvasive cases, HR−/HER2+ subtype was most common. TNBC was more common in microinvasive carcinoma than DCIS (P < .001). Among 27 microinvasive ductal carcinomas, increased TLS amount was associated with increased TILs (P = .013).
Conclusions: TLS abundance around DCIS was associated with HER2+ and TNBC subtypes and microinvasion. Pathologists should be aware of microinvasion when diagnosing DCIS lesions with abundant TLSs.