Electron spectroscopic imaging (ESI) is a recent tool for electron microscopic analysis which permits the recognition of the distribution of elements in a specimen, with a spatial resolution up to 5 nm. The authors performed the ESI together with X-ray microanalysis (EDX) and transmission electron microscopy to study granulomatous subcutaneous nodules in a patient who had undergone a desensitising therapy with an aluminium-containing vaccine. Aluminium was detected both by EDX and ESI, mainly in lysosomes of histiocytes containing needle-shaped material in a lucent matrix. However, ESI provided a better localization of aluminium with respect to EDX. This result suggests that the identification of aluminium-containing structures cannot be obtained only by ultrastructural morphology and underlines the utility of a microanalitycal study for a correct diagnosis in the presence of a needle-shaped deposition of dense material in lysosomes.