Intravascular Large B-Cell Lymphoma Within a Thyroid Nodule: A Diagnostic Pitfall

Area of Science:

• Oncology
• Hematology
• Pathology

Background:

• Intravascular large B-cell lymphoma (IVLBCL) is a rare variant of diffuse large B-cell lymphoma characterized by neoplastic cells confined within blood vessels.
• Diagnosis can be challenging due to subtle or focal intravascular involvement, potentially leading to delayed treatment.

Observation:

• A case report of a 78-year-old woman presenting with a thyroid mass.
• Ultrasound confirmed the mass, and hemithyroidectomy revealed atypical large cells in an intravascular distribution within the thyroid parenchyma.
• High-power microscopy and immunoperoxidase staining (CD20, PAX-5, Ki-67 positive) were essential for identifying the neoplastic cells.

Findings:

• The pathological findings confirmed the diagnosis of IVLBCL based on the intravascular proliferation of CD20, PAX-5, and Ki-67 positive large B-cells.
• The intravascular growth pattern was subtle and required careful high-magnification examination to differentiate from other thyroid pathologies.

Implications:

• This case highlights the importance of meticulous microscopic evaluation of thyroid resection specimens, especially when subtle intravascular atypical cells are suspected.
• Early and accurate diagnosis of IVLBCL is critical for timely initiation of appropriate treatment and improved patient outcomes.
• Awareness of IVLBCL's potential for subtle presentation is necessary for pathologists to avoid misdiagnosis.