Background: Breast cancer is one of the cancers with the highest incidence in women. Invasive breast carcinoma is found in most breast cancers and infiltrates the tissues. LC3B is a marker of autophagy and is an important protein involved in the formation of autophagosomes. The LC3B protein acts as a tumor suppressor. Therefore, lack of LC3 expression has been reported to be associated with survival and high mortality rates in TNBC. Objective: To analyze correlation expression of autophagy marker LC3B with histopathological grading and molecular subtypes in invasive breast carcinoma of no special type (IBC-NST).

Methods: This study was an analytic study with a cross sectional approach on 40 samples paraffin block with histopathological diagnosed as IBC-NST. Slides were made with routine staining of hematoxyllin eosin and immunohistochemistry LC3B. LC3B expressed on cytoplasm of tumor cells. Scores for LC3B based on multiplication proportion and intensity of staining. Correlation expression of LC3B with histopathological grading and molecular subtypes in IBC-NST was statistically tested.

Results: Most patients with IBC-NST occur age 40-49 years, with average age 50,1 years, youngest age 27 years and oldest age 73 years. Most tumor size according to T2 criteria. Most molecular subtypes were luminal. Most histopathological grading was grade 3. Immunohistochemical expression of LC3B in IBC-NST was found to be highest with strong expression.

Conclusions: The study showed a significant correlation between immunohistochemical expression of LC3B with histopathological grading (p-value 0.0001). There was a significant correlation between immunohistochemical expression of LC3B with molecular subtype (p-value <0.05). LC3B has a role as a tumor suppressor, by inducing autophagy is an effective therapeutic strategy in IBC-NST especially TNBC.