Nodular colloid degeneration: distinctive histochemical and ultrastructural features.

We recently evaluated a patient with a unique form of nodular colloid degeneration. Lesions consisted of pruritic, purpuric plaques involving the upper and lower extremities and the neck. Examination of a biopsy specimen revealed large, fissured masses of amorphous material in addition to solar elastosis. The amorphous material showed negative reactions to stains for amyloid, and other histochemical studies showed results similar to those for colloid milium. The amorphous masses demonstrated a marked positive reaction to the Verhoeff-van Gieson stain for elastin. Electron microscopic examination revealed masses of degenerated elastic tissue bordered by fibrillar material that resembled amyloid morphologically. We believe this case represents a nodular form of solar degeneration with clinical and histologic resemblances to both colloid milium and cutaneous amyloidosis.