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Storage cell macrophage on bone trephine biopsy are large cells, typically measuring 20–50 microns in size, with abundant cytoplasm and a low nuclear-to-cytoplasmic ratio. In storage disorders, these cells appear enlarged and are referred to as storage cell macrophages. The nucleus is small, round to oval, and eccentrically placed, with condensed chromatin and inconspicuous nucleoli. The cytoplasm is markedly abundant and characteristically distended by stored material, which may appear foamy, vacuolated, or fibrillary/striated depending on the underlying condition (e.g., “wrinkled tissue paper” appearance in some cases). The cytoplasmic borders are often well-defined. These cells are commonly seen in bone marrow trephine biopsies and are associated with lysosomal storage disorders, where they accumulate unmetabolized substrates within lysosomes.)