MELANOSIS ILEI

provided by Mirela Stancu, MD

Case History

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.

Microscopic Findings

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.

Diagnosis

MELANOSIS ILEI

Discussion

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.

References

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.

Anthracotic-like pigment is highlighted on a special stain for iron.
Macrophagic and extracellular pigment deposits in the superficial lamina propria. There is no histologic evidence of malignant pigmented neoplasm (H&E, high power magnification).
Macrophagic and extracellular pigment deposits in the superficial lamina propria. There is no histologic evidence of malignant pigmented neoplasm (H&E, high power magnification).
Higher power view of surface villous epithelium with reactive changes including low-cuboidal cytoplasm, loss of mucin goblets, nuclear pseudostratification and slightly increased N:C ratio (H&E, high power magnification).
Small intestinal mucosa with slightly shortened villi and benign lymphoid aggregates (H&E, medium power magnification).