We talked yesterday about differentiation. Here’s another new word to learn: anaplasia. Anaplasia refers to a lack of differentiation in neoplastic cells. Well-differentiated tumors resemble their tissue of origin, whereas poorly-differentiated or undifferentiated (anaplastic) tumor cells appear primitive and lack specialization along any particular cell line. In general, benign tumors tend to be well-differentiated. Malignant tumors run the gamut from well-differentiated to undifferentiated.

Anaplasia is not the best choice of words here, but they didn’t ask me. Anaplasia means “to form backward,” which implies that the anaplastic cells are formed from well-differentiated cells that degenerate into an undifferentiated state. This is misleading. Cancers do not arise from reverse differentiation of normal cells, but from stem cells present in all tissues. So the term anaplasia is really a misnomer. I’m just saying.

Anaplastic cells have certain characteristics (the list below is adapted from Robbins).
1. pleomorphism (variation in size and shape).
2. abnormal nuclear morphology, such as hyperchromatism (very dark nuclei), irregular nuclear contours, an increased nuclear:cytoplasmic ratio, coarse chromatin, and nucleoli.
3. Mitoses (tons of them – or, more importantly, abnormal ones, like the ones at the tips of the arrows above).
4. Loss of polarity (disrupted orientation of cells; loss of architecture and organization)
5. Other things: tumor giant cells, ischemic necrosis (from tumor cells outgrowing their blood supply)

Can you find these characteristics in the above image? You should be able to find everything except ischemic necrosis!