appendix, ALK positive ALCL
cytoplasmic and/or nuclear staining
Regulatory status: IVD, FDA Class I
8350-C010: RTU, 10 capsules; 1 pack
8350-M250: RTU, 250 tests, 1 cartridge; 1 unit
Anaplastic Lymphoma Kinase (ALK) is a transmembrane receptor tyrosine kinase. In normal tissue ALK is expressed in cells within a developing and mature nervous system including glial cells, neurons, endothelial cells, and pericytes. ALK was originally discovered as part of a fusion protein with nucleophosmin (NPM) produced by a translocation between the NPM and ALK genes and is the ALK fusion protein primarily associated with anaplastic large cell lymphoma (ALCL).
This ALK-positive anaplastic large cell lymphoma shows a characteristic sinusoidal infiltration of a lymph node. The ALK reactivity pattern is strong and is seen in both the nuclear and cytoplasmic compartments.
Moderate granular cytoplasmic reactivity for ALK is seen in this Merkel cell carcinoma. Upregulation of ALK expression in this tumor, as well as some others, including anaplastic thyroid carcinoma, appears to be though a mechanism independent of translocation.
Ganglion cells of the appendix show weak cytoplasmic reactivity for ALK, making this an excellent control tissue for this marker. The appendix shows no reactivity for ALK among the epithelial, inflammatory or smooth muscle components.