A case of histiocytic sarcoma presenting with primary bone marrow involvement

Abstract

Histiocytic sarcoma (HS) is a very rare neoplasm that often shows an aggressive clinical course and systemic symptoms, such as fever, weight loss, adenopathy, hepatosplenomegaly and pancytopenia. It may present as localized or disseminated disease. We describe here a 63-yr-old male who manifested systemic symptoms, including fever, weight loss and generalized weakness. Abdominal and chest computed tomography failed to show specific findings, but there was suspicion of multiple bony changes at the lumbar spine. Fusion whole body positron emission tomography, bone scan and lumbar spine magnetic resonance imaging showed multiple bone lesions, suggesting a malignancy involving the bone marrow (BM). Several BM and bone biopsies were inconclusive for diagnosis. Necropsy showed replacement of the BM by a diffuse proliferation of neoplastic cells with markedly increased cellularity (95%). The neoplastic cells were positive for lysozyme and CD68, but negative for T- and B-cell lineage markers, and megakaryocytic, epithelial, muscular and melanocytic markers. Morphologic findings also distinguished it from other dendritic cell neoplasms.

Keywords: Bone Marrow; Histiocytic Sarcoma.

Fig. 1

Scanning findings for bones. (A) Disseminated hypermetabolic lesion (maxSUV=9.0, L2 body) at the whole spine by PET. A hypermetabolic lesion suggesting a primary malignant lesion was not detected in the lung, intraabdominal and pelvic organs. (B) No increased bone uptake of hypermetabolic lesions on bone scan, with little osteoblastic effect.

Fig. 2

Diffuse and heterogeneous T1 and T2 showing low SI changes in the lower thoracic and lumbar spine with subtle enhancement.

Fig. 3

Histopathological findings of bone marrow biopsy. (A) Non-cohesive proliferation of large pleomorphic neoplastic cells with large round-to-oval nuclei with vesicular chromatin and abundant foamy cytoplasm (H&E stain, ×400). Immunostaining with antibodies to (B) CD99, (C) CD68, (D) CD56, (E) HMB45 (each, ×100) and (F) S100 (×200).