Giant brown cells among the lymphocytes

Dear all,

Can you help me identify the type of cells seen in this picture? 

I'm establishing cultures of T-cells from tumour fragments (melanoma patients). Sometimes we see some large dark cells around the tumour fragment and among the proliferating lymphocytes. They typically appear after a couple of weeks of culturing and then later seem to die out - or at least they are totally outnumbered by the proliferating T-cells.

Some of my colleagues think they are apoptotic tumour cells; others speculate if they are in fact clusters of minor cells of some type. The small white cells in the picture are T-cells (diam. 10-15 um), and you can also see a "clonal ball of T-cells" in the lower left corner. To me the dark cells look like "giant" single cells.

Could they for instance be melanophages - or do they look malignant? The tumour as such was dark brown (melanin).

Please, let me know if you have any suggestions : ) All comments are very welcome!


Best regards,

Vitting - Denmark

I'll try to uploade the picture - again. Something went wrong before.

Vitting

Are these in round or flat bottom plates? Can you do a quick DAPI stain in situ when it happens, and observe in an inverted fl scope?
It might actually be T cell 'activation clusters' (T cells can function as weak +ve and moderate -ve (tolerogenic) APCs in T-T interactions) especially if they are in rounded bottom plates (or high enough density in flat bottom plates) - you see that with PMA+I stimulation. However, it can also be cell fragments or some form of contamination - hence, the DAPI will be informative.
Best,
sam