Adenosis

 

Adenosis is a benign proliferation of small glands that form a nodular lesion which is poorly circumscribed. The glands are tightly packed and may become so small that they seem to infiltrate the stroma, especially towards one end of the lesion. There is a gradual transition between large, obviously benign glands and small glands that mimic cancer.

  

The nuclei may be slightly atypical with some nuclear enlargement. The nucleoli may be visible but are usually not as prominent as in cancer. The chromatin is pale and bland-looking and the variation in size and shape, that is so typical for cancer, is not seen.

Immunohistochemistry for basal cells is helpful. A patchy distribution of basal cells is typical for adenosis. Glands that are negative for basal cell markers are otherwise morphologically similar to glands with preserved basal cell layer.