oh I'm sorry, I went to bed assuming you weren't coming back! Right. Let's see.
First thing that springs to mind is 'In situ' - which basically means, this melanoma has NO capacity to spread - it's just right on the surface. That means no need to do anything like an SNB etc, this is the very earliets stage and unlike the next type, ie a stage 1A, it just hasn't penetrated below the top layer so it is v v unlikely to have travelled anywhere else. This is the VERY best news
No ulceration also brill (the top layer of it hasn't broken - ulcerated is bad news)
No mitosis - this means it's not aggressive. Mitotic rate is how fast it is growing/multiplying within itself, and it's basically, well, not not enough to measure anyway.
No regression means they don't think it's grown and then 'gone back' again into the skin, which some do so that is again good.
'macroscopic' means what they can see at first hand, say in the Dr's surgery. Microscopic is what they know after they've had a look under a microscope (no really!)
From the beginning then:
What Dr could see: a thing on your skin, 9x7x5mm with a dark brown coloured spot 6mm wide at most. This has got different colours in it and an irregular border. 2mm from the nearest [short axis margin] no idea what that is. Bisected means divided in two, don't understand the cassettes bit, orthe TS or RS.
What they saw in the lab: lOOKS like a lesion made of melanoma cells, joined somehow to some other mole you already had? Severe cytological atypia means it's made of very suspicious cells, ie not your usual mole structure. Proliferation confluent means where the weirdy cells have grown, they're joining up with this other thing. (this part is a bit confusing, sorry)
Underlying dermal component is the thing you already had, I think, which is mature and has depth (but that's not the nasty thing, as it's not atypical?) Mitoses, see before.
They think it is a superficial spreading melanoma which has grown out of a CDMN (mole).
They think they got it all, with a margin of 1.6mm. They have probably got you back in to do a wider excision, and they'll test the bit they took out to make sure there are no more cells around it that were missed.
All in all you have a great result there and despite the follow ups, I think you're very likely to be fine
HTH!!