Lymph node interdigitating cell granuloma associated with non-Hodgkin's malignant lymphoma. A case report and review of the literature.

We report a new case of histiocytic proliferation, which histologically resembles histiocytosis X, in a lymph node affected by non-Hodgkin's malignant lymphoma. This brings the total number of such reported cases to 12. Histiocytosis X cells, with folded nuclei, expressed S100 protein and an antigen recognized by anti-CD1 monoclonal antibodies. Ultrastructural study did not show any Birbeck granules and demonstrated a morphology similar to that of interdigitating cells. In the absence of Birbeck granules, the term 'Langerhans' cell granulomatosis' is not correct and should be replaced by either 'interdigitating cell granuloma' according to immunohistochemistry and ultrastructure or 'histiocytosis X-like granuloma' according to optical morphology. The fact that some cells with folded nuclei were positive for lysozyme argues in favor of the existence of transitional cells between histiocytes hnd interdigitating cells. The 11 other reported cases were reviewed. In 6 cases, this type of granuloma was associated with B cell lymphoma. In 3 cases the lymphoma was also probably of B cell type. In 2 cases, no information could be found. We could speculate that these histiocytosis X-like lesions are reactive, resulting from immune disturbances due to the lymphoma and/or the treatment.