Figure 2.

Transdifferentiation of mammary alveolar epithelia to epidermal structures. (A) At pregnancy day 15, the gland was heterogeneously differentiated. Evidence of normal alveolar structures (B) and hyperproliferative epidermal cysts containing ghost cells (C). (D) At lactation day 1, the transdifferentiated lesions were more widespread. (E) Evidence of apparently normal secreting alveoli and (F) hyperproliferative epidermal cysts containing ghost cells. (G) Ten weeks after involution, we preferentially detected squamous metaplasias. (H) Cells were consistently hyperplastic and the center of the nodule was keratinized. (I) Evidence of the epidermal appearance of these structures.