[Clinicopathologic and immunophenotypic analysis of myeloid sarcoma]

Area of Science:

• Hematopathology
• Oncology
• Diagnostic Pathology

Background:

• Myeloid sarcoma is an extramedullary tumor of myeloid blasts.
• It can occur independently or in association with myeloproliferative disorders.
• Accurate diagnosis is crucial for appropriate management.

Purpose of the Study:

• To delineate the clinicopathologic characteristics of myeloid sarcoma.
• To assess the utility of immunohistochemical markers in diagnosing myeloid sarcoma.
• To correlate morphology and immunophenotype with clinical outcomes.

Main Methods:

• Retrospective review of 82 myeloid sarcoma cases (1990-2005).
• Morphologic classification based on the 2001 WHO criteria.
• Immunohistochemical analysis using 11 antibodies on 73 cases.
• Survival data analysis using SPSS 10.0.

Main Results:

• Median age was 35.5 years; male-to-female ratio 1.4:1.
• Common sites: lymph node (43.1%), skin (16.7%).
• 62.2% associated with myeloproliferative disorders; 30.5% solitary.
• Granulocytic sarcoma (96.3%) with blastic (51.9%) and immature (31.6%) types.
• Immature eosinophils present in 64.6% of granulocytic sarcomas.
• High positivity for myeloperoxidase (95.9%) and lysozyme (95.5%).
• CD68 (KP1) positive in 95.2%; CD68 (PG-M1) in 4.7% (suggesting monocytic differentiation).
• Two- and five-year survival rates: 36.1% and 17.3% respectively; no significant prognostic factors identified.

Conclusions:

• Myeloid sarcoma can precede, occur with, or follow myeloproliferative disorders.
• Immature eosinophils are a key morphologic indicator.
• Immunohistochemistry, particularly myeloperoxidase for granulocytic and CD68 (PG-M1) for monocytic differentiation, is vital for diagnosis.
• Clinicopathologic correlation enhances diagnostic accuracy.