Canine malignant lymphomas: comparison of morphologic and immunologic parameters

Area of Science:

• Veterinary Pathology
• Immunology
• Canine Oncology

Background:

• Canine malignant lymphoma is a common cancer with diverse presentations.
• Understanding the immunophenotype and morphology is crucial for accurate diagnosis and treatment.

Purpose of the Study:

• To correlate morphologic features with immunologic properties of neoplastic cells in canine malignant lymphomas.
• To determine the B-cell or T-cell lineage of lymphoma cells.
• To investigate the biological heterogeneity and homogeneity of different lymphoma subtypes.

Main Methods:

• Histologic classification (cell type, growth pattern) and anatomic distribution analysis.
• Transmission electron microscopy (TEM) for ultrastructural examination.
• Immunologic assays including mitogen responsiveness, cell-surface immunoglobulin (Ig) detection, and scanning electron microscopy (SEM) for cell-surface features.

Main Results:

• Cells from histiocytic lymphomas were identified as lymphocytes, not histiocytes or macrophages.
• Most canine lymphomas expressed cell-surface Ig, indicating a B-cell origin, with subtypes potentially representing different lymphocyte differentiation arrest stages.
• Diffuse, poorly differentiated lymphocytic lymphomas were biologically heterogeneous, while nodular histiocytic lymphomas were homogeneous.
• Lymphoma patterns in lymph nodes correlated with distinct splenic involvement patterns.
• SEM revealed predominantly smooth-surface cells in both Ig-positive and Ig-negative neoplasms.

Conclusions:

• Canine malignant lymphomas exhibit diverse morphologic and immunologic characteristics.
• The B-cell origin is common, with subtypes potentially linked to lymphocyte differentiation.
• Distinct patterns of lymph node and splenic involvement suggest different disease progression pathways.