I think this would not be an easy task if at all possible (which I doubt) sorry.
It's a bit like people who say Oh I play the guitar only to discover most of them do so,(badly).In other words .Yes it can be repaired, but I don't believe it can be done without noticing it.Best of luck Thrud has the proper answer as I see it.
In My opinion You would need to make a plaster cast to hold all the pieces together fixing them first with removable glue actually not plaster as it would crack but a casting material similar to that used for casting or soldering gold.Then grind when set all the pieces would have to be taken apart and ground and roughened out around the cracks. Then reassembled onto the mould (jig)after all the pieces must be fixed together under heat and not move /misalign while it is being done then weld it all back together filling the pieces you had ground away from the cracked area with new glass rod then regrind it and repolish it and probably re monogram any bits in the damaged area. An expensive job suited only for very few skilled people who could handle such a task.Sorry I don't think this is feasable perhaps it could be done another way I don't know. Alistair
Please excuse my typing as I have a form of parkinsons disease