Papillary carcinoma- Thyroid

  • Most common thyroid malignancy

Gross:   The tumor is usually solid, white and firm. Can be cystic.  Also sometimes it can be multifocal
Microscopy:    The classical  features will be presence of complex, branching papillae with fibrovascular cores.
THE most important feature are its nuclear features. They are
a.Nuclear overlapping:  the nuclei are so crowded that they look like they are sitting on one another!

b.Ground glass nuclei : it means the chromatin is finely dispersed and optically clear. This appearance is also known as “Orphan Annie Eye” appearance. Annie is a character in an American comic strip “little Orphan Annie”.    Vacant circle for eyes was one of the distinguishing feature of Annie. The nuclei being clear looks like an eye of Annie!
c.Intranuclear inclusions:  This is actually  a cytoplasmic invagination into the nuclei.  So the inclusion is eosinophilic, the color of the cytoplasm
d.Nuclear groves:  The groves  are longitudinal and are formed due to folding of  the unessential nuclear membrane
The last two are nonspecific though. Well, there is no proper understanding as to why the nuclei are like this!
Other useful findings:
Psammomma bodies: they are concentric laminations of calcification. This is an example of dystrophic calcification. We all know that dystrophic calcification occurs in dead and degenerated tissue. In this case, the calcification occurs due to death of tumor cells, particularly at the tips of the papillae. The blood supply from the cores might not be sufficient for the tumor cells, which are rapidly growing , particularly at the tips. Hence the cell dies.. Replaced by calcification!
one worthwhile point to remember here is “  the distinct nuclear features” are the ones which are specific and NOT the  presence of papillae.
Tumor without papillary architecture can still be papillary if the above mentioned nuclear features are present.This is called “Follicular Variant” of Papillary carcinoma.