Diffuse large B-cell lymphoma initially manifesting in the bone marrow.

Area of Science:

• Hematology
• Oncology
• Pathology

Background:

• Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous lymphoid malignancy.
• Bone marrow (BM) involvement is common in DLBCL, but primary BM manifestation is less understood.
• Distinguishing primary BM DLBCL from other large B-cell lymphomas is crucial for accurate diagnosis and treatment.

Purpose of the Study:

• To characterize the histological and immunohistochemical features of DLBCL primarily manifesting in the bone marrow.
• To compare these cases with the Asian variant of intravascular large B-cell lymphoma (AIVL).
• To determine if primary bone marrow DLBCL represents a unique clinicopathological entity.

Main Methods:

• Histological examination of 37 bone marrow biopsy specimens from DLBCL cases.
• Immunohistochemical analysis using B-cell markers.
• Factor VIII staining to identify neoplastic cells within bone marrow sinusoids.
• Comparison with clinical and pathological features of AIVL.

Main Results:

• Neoplastic cells in primary bone marrow DLBCL typically exhibited large, round nuclei and formed clusters.
• All cases were positive for B-cell markers.
• While 8 cases showed neoplastic cells in BM sinusoids, they comprised <20% of the total neoplastic cells.
• Leukemic infiltration of organs like the liver, spleen, and kidneys was observed, predominantly in a leukemic rather than intravascular pattern.

Conclusions:

• DLBCL primarily manifesting in the bone marrow is a distinct entity.
• It differs from AIVL due to predominant BM proliferation and infrequent sinusoidal involvement.
• Occasional leukemic infiltration in other organs characterizes this unique DLBCL subtype.