A case of histiocytic sarcoma presenting with primary bone marrow involvement

Area of Science:

• Oncology
• Hematology
• Pathology

Background:

• Histiocytic sarcoma (HS) is an exceptionally rare neoplasm characterized by aggressive behavior and systemic manifestations.
• Common symptoms include fever, weight loss, lymphadenopathy, enlarged liver and spleen, and pancytopenia.
• HS can present as either localized or widespread disease.

Observation:

• A 63-year-old male presented with systemic symptoms like fever, weight loss, and generalized weakness.
• Initial imaging studies were inconclusive, but suggested bone abnormalities in the lumbar spine.
• Advanced imaging and multiple biopsies failed to provide a definitive diagnosis.

Findings:

• Necropsy revealed the bone marrow was almost entirely replaced by a diffuse proliferation of neoplastic cells (95% cellularity).
• Immunohistochemical analysis showed neoplastic cells were positive for lysozyme and CD68.
• The cells were negative for lymphoid, megakaryocytic, epithelial, muscular, and melanocytic markers, differentiating it from other dendritic cell neoplasms.

Implications:

• This case highlights the diagnostic challenges posed by histiocytic sarcoma, particularly when presenting with non-specific systemic symptoms.
• Definitive diagnosis was only achieved post-mortem, underscoring the need for advanced diagnostic techniques.
• Accurate identification of histiocytic sarcoma is crucial for understanding its aggressive nature and for developing targeted therapeutic strategies.