The analysis of urine sediment is a diagnostic test that can provide useful and relevant information in a large spectrum of clinical situations. Crystalluria is a common finding and its present in both normal and pathological conditions. A wide variety of crystals may be observed in urine sediment and can be identified based on the morphology and solubility characteristics. Figure C-1 shows an unusual structure that was initially misinterpreted as an uncommon crystal in urine sediment from a 72-year-old man with haematuria. The sample was processed by conventional cytocentrifugation, fixed in 96% ethanol, and stained with the Papanicolaou method. On review, this structure is a pollen grain belonging to genus Alnus glutinosa (alder tree, Betulaceae family). This pollen grain is *20‐30 lm in diameter, has a pentagonal morphology with five apertures, and radial symmetry. Outer and inner layers (extine and intine) of the wall are visible. It does not show birefringence under polarized light. As previously reported in pap smears, 1 the most likely source is airborne contamination during the staining of the smear. In Europe, Alnus pollen is considered an important aeroallergen. 2