Yonago Acta medica 1992;35:231–240

Histiocytic Sarcoma (True Histiocytic Lymphoma): Report on a Case

Makoto Motoi, Yukisato Kitamura, Masako Kato, Hideo Akiyoshi, Keiichi Ichihara and Tadashi Yoshino*

Second Department of Pathology, Faculty of Medicine, Tottori University, Yonago 683 and *Second Department of Pathology, Okayama University Medical School, Okayama 700, Japan

Since it became clear that the majority of the formerly so-called histiocytic lymphomas are considered to be of lymphocytic origin, there have been only a few reports of true histiocytic lymphomas, i.e., histiocytic sarcomas. In this paper we present a typical case of histiocytic sarcoma. The subject, a 72-year-old male, had a goose egg-sized tumor in the axillary region. Histologically, the tumor was composed of a diffuse proliferation of medium to large cells consisting of abundant, eosinophilic cytoplasm, round or oval nuclei with some mitoses and one to two nucleoli. A considerable number of tumor cells displayed phagocytosis. The tumor cells were positive for acid phosphatase, lysozyme, α1-antitrypsin and KP-1, while negative for κ and λ light chains of immunoglobulins, L26, Leu 1, 2a, 3a+3b and 4, and UCHL-1. Electron-microscopically, the tumor cells had a large amount of lysosomes and pseudopodial structures, and showed intracytoplasmic phagocytoses. These cellular characteristics demonstrated that the tumor cells exhibited evidence of monocyte-histiocyte differentiation. Therefore, this tumor was considered to be a primary histiocytic sarcoma of the soft tissue.

Key words: histiocytic sarcoma; soft tissue; immunohistochemistry; electron microscopy

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