New electron microscopic findings in a case of multicentric reticulohistiocytosis. Long spacing collagen inclusions.

The case of a 68-year-old woman with polyarthropathy and skin nodules is presented. Histologic findings of histiocytes with ground-glass cytoplasm favored the diagnosis of multicentric reticulohistiocytosis. In this article we report new electron microscopic findings of intra- and extracytoplasmic long spacing collagen (type VI). Type VI collagen inclusions are usually found in lymphohistiocytic neoplasms. We believe our findings support the concept of a proliferative rather than inflammatory etiology for multicentric reticulohistiocytosis. It may also give support for the argument of production of collagen by the histiocytic cells of multicentric reticulohistiocytosis.