University Pathologists - Case of the
Month -
CASE ARCHIVE > MELANOSIS ILEI
provided by Mirela Stancu, MD
A 45 year-old man presented to the office complaining of intermittent chronic diarrhea.
The colonoscopy to terminal ileum showed normal colonic mucosa and 2 large raised mucosal
patches in the terminal ileum, averaging 2cm in maximum dimension, clinically suspicious
for malignant melanoma.
The mucosal fragments from the terminal ileum show a high density of lymphoid follicles
in the superficial lamina propria, associated with the surface epithelium (Peyer's
patches). The villi are slightly blunted and are lined by reactive surface epithelium with
low columnar cells, nuclear pseudostratification and loss of goblet cells. There is no
acute inflammation identified in any of the fragments, and no significant chronic
inflammation. No malignant infiltrate is observed in any of the fragments. On higher power
view, a finely granular dark-brown pigment similar to the anthracotic pigment commonly
found in lung parenchyma or thoracic lymph nodes, is noted. The pigment has both
intracellular and extracellular distribution, and is present throughout mucosa. The
pigment doesn't stain with iron or melanin histochemical stains.
MELANOSIS ILEI
Melanosis ilei is a pathologic condition characterized by grey-black or dark-brown
mucosal pigmentation of the terminal ileum. Two forms may be recognized: 1) one form
associated with melanosis coli; and 2) a second form in which there is ileal pigmentation
alone.
Melanosis ilei is an incidental finding at colonoscopy or post-mortem examination. On
light microscopy, the pigment is dark-brown, granular and lays within macrophages in
atrophic Peyer's patches. Ultrastructural studies showed that the pigment granules are
heterolysosomes containing crystalline material, particles, granules and, occasionally,
lipid droplets. Electron microscopy studies performed on autopsy pathologic material
reported morphologic and content similarity between the pigment granules of melanosis ilei
and the anthracotic pigment present in macrophages of pulmonary lymph nodes. X-ray
analysis showed that the pigment granules present in melanosis coli contains aluminium and
magnesium-rich silicates derived from the atmospheric dust.
In a case of melanosis duodeni and peptic ulcer, iron and aluminum, magnesium and silicon
were found in the pigment granules, attributable to anti-acid medication and iron tablets
in this particular patient.
In summary, melanosis ilei is most likely the result of macrophagic deposits of exogenous
material derived from inspired and ingested materials.
1. Ghadially FN, et al. A comparison of the ultrastructure of pigment granules in
melanosis ilei and pulmonary lymph nodes. Histopathology 1993;23:167-172.
2. Won KH, et al. Melanosis of the ileum. Am J Dig Dis 1970;15:57-64.
3. Urbansky SJ, et al. Pigment resembling atmospheric dust in Peyer's patches. Mod Pathol
1989;2:222-226.
4. Shepherd NA, et al. Exogenous pigment in Peyer's patches. Hum Pathol 1986;18:50-55
5. Pounder DJ, et al. Ultrastructure and electrone-probe x-ray analysis of the pigment in
melanosis duodeni. J Submicrosc Cytol 1982;14:389-400.
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