Microscopic description and IHC:

The excised lesions show numerous foamy macrophages in a background of mixed acute and chronic inflammatory cells including plasma cells.

CD163 highlights the foamy macrophages. Warthin-Starry stain highlights bacterial rods inside the foamy macrophages.

Discussion:

Rhinoscleroma, also known as simply scleroma, is a rare granulomatous disease caused by the gram negative bacillus Klebsiella rhinoscleromatis. Nasal cavity is the most frequently affected area. It is an endemic tropical disease mostly in Africa and Central America. It is a non-lethal disease that can be easily treated with antibiotics.

References:

ANDRACA, RAFAEL, RANDALL S. EDSON, and EUGENE B. KERN. "Rhinoscleroma: a growing concern in the United States? Mayo Clinic experience." Mayo Clinic Proceedings. Vol. 68. No. 12. Elsevier, 1993.

CASE IMAGES