Sinus Histiocytosis with Massive Lymphadenopathy

Differential Diagnosis

S100 staining of large vesicular nuclei is rarely seen in reactive sinus hyperplasia

Langerhans cell histiocytosis is composed of S100 positive histiocytes that may have a sinusoidal distribution

Langerhans Cell Histiocytosis	Sinus Histiocytosis with Massive Lymphadenopathy
Small to medium sized nuclei	Large nuclei
Grooved, folded nuclei	Round, vesicular nuclei
Inconspicuous nucleoli	Prominent nucleoli
CD1a positive	CD1a negative
No emperipolesis	Prominent emperipolesis
Eosinophils frequent	Eosinophils not frequent
Capsular fibrosis infrequent	Capsular fibrosis frequent
Plasmacytosis infrequent	Plasmacytosis frequent

Both are S100 positive.