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ALK-Negative ALCL
Lessons from the Friday Unknowns
Histologic sections show fragments of lymph node involved by lymphoma. The lymphoma shows a sinusoidal infiltration pattern, and is composed of large pleomorphic cells, with irregular nuclear contours, open chromatin, visible nucleoli, and variable amounts of eosinophilic cytoplasm.
Numerous forms with horseshoe-shaped nuclei or “hallmark” cells, as well as scattered tumor cells with bilobed and multilobed nuclei are present. There are numerous mitotic figures and single-cell apoptotic bodies. Frequent eosinophils, small lymphocytes and histiocytes are seen in the background.
The neoplastic cells are positive for CD30 (strong membranous and Golgi pattern), CD4 (weak, subset) and CD2 and they are negative for CD19, ALK, granzyme B, CD3 and TCR BF 1. The proliferation index measured by Ki-67 is approximately ~90–100% of neoplastic cells.
Flow cytometric analyses were performed in the sample and show an abnormal T-cell population representing 10% of total lymphocytes, with decreased expression of CD3, CD5 and CD7 and negative for CD4 and CD8. Immunohistochemical stains were performed in the specimen…
