Urinary schistosomiasis due to Schistosoma hematobium. This patient is at risk for squamous cell carcinoma of the bladder, caused by ongoing squamous metaplasia and inflammation from the eggs present in the bladder wall.
In histologic sections, the eggs are typically seen in various stages of degeneration and calcification. Here, some degenerating nuclei are present within the egg (H&E, 1000x).
To make a diagnosis to the species level, you need to see a clearly identifiable terminal spine. The spines of these eggs are fairly clear (arrows):
and are even more pronounced in this image from a separate case:
When urinary schistosomiasis is suspected, examination of urine for characteristic eggs is a non-invasive way to make the diagnosis.