As leo-a-go-go said, "...no way of speciating it by microscopy alone, without a geographic history. Would be useful to know if offending fish was from salt or freshwater." Anonymous also noted that "If the patient is from South America, might be D. pacificum rather than D. latum." Worldwide, D. latum is the most frequently reported species in humans. However, the DPDx web site notes that "Several other Diphyllobothrium species have been reported to infect humans, but less frequently; they include D. pacificum, D. cordatum, D. ursi, D. dendriticum, D. lanceolatum, D. dalliae, and D. yonagoensis."
Diphyllobothrium spp. proglottids are easily recognized by the fact that they are broader than they are long (hence the name 'broad fish tapeworm') and the characteristic 'rosette' shaped uterus:
Better examples of the rosette-shaped uterus can be seen from previous cases HERE.
And now, our weekly poem from Blaine Mathison:
All that raw fish, you really shouldn’t have ate ‘em
cuz now you have Diphyllobothrium latum
you did it on a dare
never mind the potential scare
Your buddy who bet you? I bet you now hate him!