LOL! Trace it again more carefully, and then two more times for good measure, making sure some volunteer or other plant didn't get in there somewhere! That is still the most likely explanation.

But if it really is a tomato with multiple locules it is conceivable it is a "sport" - a mutation in the tissue but not in the pollen or ovaries, which is usually not an inheritable trait, and means if you save seed you'll likely just get the cherry back and lose the mutated tomato if that really is the case. But you never know if it made it to the DNA - anything is possible in genetics, though improbable.

By cloning the stem of it assuming it is the stem and not restricted to the fruit, you would get the same tomato back (sport or otherwise). I say keep it going if you can possible find the time. Many interesting cultivars were developed from this type of mutation. Probably this is the sort of mutation the pre-Colombian breeders of the tomato found to turn fat currant like tomatoes into the domesticated tomato, where it is proposed this is due to the amazing FAS gene mutation (Fasciated).

Tomato domestication (Muñoz et. al. 2011)

Or, it is possible you have an impure line as cherry tomatoes are thought to maybe be creoles of sorts, having DNA from a mixture of domesticated tomatoes and wild currants, though it is hard for me to understand how you could have won the lottery with this reversion :-)

Does the cluster have any other tomatoes and how is the architecture of the cluster - cherry like? How about other clusters on the same stem which are easier to locate than following the stem to the ground level?

Interesting if true!

Cheers

PC

As PC said probably you have impure seeds OR there is another variety mingled with it. I have lots of those. Big Beef and Ananas Noire are growing and fruiting as if it is a single plant.

Too bad you can never know with 100% certainty but at least it looks like you've taken a good crack at solving the mystery. This is one rogue wherever it's from that will be interesting to see mature if the tomato resembles any variety you might relate to. I plant several varieties in my starter flats and once I recall a seed I might have imagined stuck to my knifehand surface and I thought it might have fallen in the flat. I was absolutely sure someone gave me the wrong seed 3-4 months later, but then the image of what happened randomly got revived somehow in my head. Sometimes you need a photographic memory with instant replay to trace these things!

Congrats on following the stem. Just getting the picture inside the cage was enough to get me dizzy. My Dad when I was young taught me how to look for problems in the spaghetti wired engines of foreign cars and this reminds me of that. He would take bread twist-ties and wrap them on what he was following from the top and then get under the car and find it from the bottom or sides and repeat until he found whatever it was. Thanks for the good memory!

Cheers

PC

In fact, the "flag markers" I used to trace the stem were twist-ties. Good idea! I use those ties routinely for tying up my tomatoes onto my trellises. (So I guess even then there was some potential for confusion.) Gee, it's possible, I suppose, that the rogue seed got there through my own sloppiness, but I planted my cherries and slicers a week apart. I like mysteries, and the detective-ing needed to figure them out. Gardening is full of those mysteries, really.

Agreed! Nothing like an old-fashioned mystery just when you think you're in the rocking chair lazily catching your breath and watching plants grow, when they find yet another thing to keep you on your toes.

Cheers

PC