Anaplastic large cell lymphoma, ALK negative
Clinical history:
38 y/o M with enlarged neck node.
Immunohistochemistry:
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- ALK – There is no expression of ALK in the neoplastic cells.
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- CD3 – The large, neoplastic cells are CD3+, as are scattered benign T cells in the uninvolved portion of the node.
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- CD30. The malignant cells are strongly CD30+
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- Mum-1
CLINICAL FEATURES AND PATHOGENESIS
• Peak incidence in adults, age 40-65 years
• Primary to lymph nodes (most cases) or extranodal sites (bone, soft tissues, skin)
• Worse prognosis than Anaplastic large cell lymphoma, ALK+, but probably better than Peripheral T-cell lymphoma, not otherwise specified
MICROSCOPIC FEATURES
• Nodal or tissue architecture effaced by solid sheets of malignant cells, often within sinuses at the periphery
• Large, pleomorphic, mitotically active cells, often with prominent nucleoli and moderate to high N:C ratio
• Horseshoe-shaped “hallmark cells” or cells with wreath-like nuclei may be present.
ANCILLARY STUDIES
• Uniform, strong CD30+ and ALK-1 negative by definition
• Loss of pan T-cell markers is common, but usually at least one of CD2, CD3, CD5 or CD43 is positive.
• Often positive for EMA, CD4 and/or cytotoxic T-cell markers such as TIA1, granzyme B, and perforin
• Negative for Pax5, EBER, and usually CD15 (vs. CHL) and keratin (vs. carcinoma)
DIFFERENTIAL DIAGNOSIS
• Anaplastic large cell lymphoma, ALK positive
• Peripheral T-cell lymphoma, not otherwise specified
• Classical Hodgkin lymphoma (especially syncytical variants)
• Primary cutaneous anaplastic large cell lymphoma (in skin)
• Enteropathy-associated T-cell lymphoma (in GI tract)
REFERENCES
•WHO Classification of Tumors of Haematopoetic and Lymphoid Tissues, 4th edition
