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mammary epithelial proliferation

Wednesday 12 December 2012

Epithelial proliferation can lead to two different patterns:
- An increase in the number of layers of cells, which causes filling of glandular lumens and distention of the glands.
- A less commonly appreciated pattern of proliferation develops when the cells grow as a single layer rather than piling up.

  • This manner of growth causes enlargement of the structures without filling of their lumens.
  • In fact, the lumens become distended and look like tiny cysts.
  • The notion that such a pattern could reflect an increase in the number of cells strikes many observers as odd, but even an approximate calculation of the number of cells present on the walls of such structures makes clear that the epithelial cells have multiplied.

The proliferative cells lining proliferative glands crowd together, and this close packing causes them to assume columnar shapes.

The nuclei become oval, and when extremely crowded, they sit at different positions in the cells, thereby creating a pseudostratified appearance.

The cytoplasm collects at the apical pole of the cells and sometimes forms small blebs.

When one observes cells with these characteristics lining distended glands, one can reliably identify the presence of cellular proliferation.

Differential diagnosis

- microcysts

  • Cellular proliferation does not underlie the formation of every distended gland.
  • The microcysts that constitute a component of fibrocystic changes develop because of an imbalance in secretion and adsorption.
  • One can recognize such cysts from the flat and inconspicuous appearance of their lining cells, features that contrast with those of cells lining proliferative glands.