What histological feature differentiates fibroadenoma from breast carcinoma?

The histological feature that differentiates fibroadenoma from breast carcinoma is the well-circumscribed borders found in fibroadenomas. Fibroadenomas are benign tumors characterized by their distinct and well-defined edges, which allows them to be easily distinguished from malignant lesions during histological evaluation. This clear demarcation indicates that the fibroadenoma is not invading surrounding tissues, a hallmark of malignancies such as breast carcinoma.

In contrast, breast carcinoma frequently exhibits infiltrative growth patterns with poorly defined borders, allowing the cancerous cells to invade adjacent tissues. The presence of invasion is a critical factor that signifies malignancy, whereas the well-circumscribed nature of fibroadenomas suggests a benign lesion.

Other features such as necrosis, presence of calcifications, and invasion are more related to malignancy and do not characterize fibroadenomas. For instance, necrosis typically occurs in more aggressive tumor types, while calcifications can be found in both benign and malignant lesions. The distinction in border characteristics is thus essential in histopathological assessment for differentiating between these two types of breast lesions.