Histiocytic disorders of the gastrointestinal tract

The morphologic diagnosis of histiocytic lesions of the gastrointestinal tract can be challenging, and several disorders have to be considered in their differential diagnosis. We present one of the most widespread examples of xanthomatosis of the gastrointestinal tract published so far and give a short review on histiocytic disorders of the gastrointestinal tract in general. The primary histiocytic disorders of uncertain origin, Rosai-Dorfman disease, Langerhans cell histiocytosis, and Erdheim-Chester disease, are addressed. Reactive and infectious conditions such as xanthomatosis, xanthogranulomatous inflammation, juvenile xanthogranuloma, Whipple's disease and malacoplakia are discussed as well. We also briefly go into primary histiocytic disorders of neoplastic origin, systemic diseases with secondary gastrointestinal tract involvement like the lysosomal storage disorders, and pigmented lesions. Using a panel of histochemical stains and immunohistochemical markers, together with conventional microscopy, clinical information, and imaging studies, the diagnosis of histiocytic disorders of the gastrointestinal tract can be established in most instances.