ALK is a protein, 200 kDa, a transmembrane receptor tyrosin kinase, presumably receptor for the growth factor pleiotrophin. In normal tissues, ALK protein is expressed only few cells within the developing and mature nervous system (glial cells, neurons, endothelial cells and pericytes) (11-13). The ALK gene was discovered in the late 1980s, when it was noted that CD30+ anaplastic large cell lymphomas (ALCLs) may be associated with a balanced (2;5)(p23;q35) chromosomal translocation in some cases (1-5). Subsequently, cloning of the chromosomal breakpoints identified ALK gene, which was located at chromosome 2p23, and NPM (encoding ubiquitously expressed nucleophosmin), located at 5q35 (6). The resulting NPM-ALK hybrid protein (also known as p80) contains 40% of the amino-terminal portion of NPM linked to the entire cytoplasmic domain of ALK (7-10).
The t(2;5) translocation that involves the ALK gene accounts for about 80% of the ALCL cases (14) (Fig. 1). In the remaining cases, other variant rearrangements involving ALK gene are seen, including t(1;2)(q21;p23), inversion 2(p23;q35), t(2;3)(p23;q21), t(2;17)(p23;q23), and t(X;2)(q11-12;p23). In these uncommon rearrangements ALK gene is juxtaposed to TPM3, encoding a nonmuscle tropomyosin; TFG (TRCK fusion gene), encoding a polypeptide with a predicted coiled:coiled domain; ATIC, which encodes an enzyme, 5-aminoimidazole-4-carboximide-1-ß-D-ribonucleotide transformylase/inosine monophosphate cyclohydrolase, that participates in purine metabolism; CLTC, encoding the clathrin heavy-chain gene; or MSN, encoding moesin, a member of the protein 4.1 family of membrane-associated polypeptides(15-20). ALK gene is translocated not only in ALCL, but also in inflammatory myofibroblastic tumor. Tropomyosin 4 and RANBP2 genes were found involved only in inflammatory myofibroblastic tumor, nucleophosmin and TRCK fusion gene in ALCL only, while tropomyosin 3, and clathrin heavy chain genes were found involved in rare cases of both ALCL and inflammatory myofibroblastic tumors (27,28). ALK has also been detected by immunohistochemistry in some sarcomas, particularly rhabdomyosarcoma (29). However, in most of the soft tissue tumors, except the inflammatory myofibroblastic tumors, it displayed merely low-level expression. It has also been described in some cases of neuroblastoma (30). ALK1 can also be expressed in diffuse large B cell lymphoma (DLBCL). These are unique DLBCL with monomorphic large immunoblast-like cells, containing large central nucleoli, which tend to invade lymphatic sinuses. Superficially they resemble anaplastic large cell lymphoma (ALCL) but they lack CD30. These lymphomas express epithelial membrane antigen (as do ALCL), but also contain cytoplasmic IgA (31). In contrast, CD30-positive DLBCL are ALK1-negative. ALK-positive ALCL usually present in young men, presenting with advanced disease (stage III or IV), are commonly associated with fever, and there is extra nodal involvement. However, they respond well to chemotherapy and have a favourable outcome (24,25). Interestingly, ALK-positive ALCL are consistently BCL2-negative (26).
The main application is classification of malignant lymphomas, viz. identification of ALCL. Furthermore ALK is important for the identification of inflammatory myofibroblastic tumors.
Appendix is recommendable as positive and negative external tissue control, in which ganglion cells of the myenteric plexus and dispersed axons must show an at least weak to moderate staining reaction and no staining should be seen in smooth muscle cells and epithelium.
Lung adenocarcinomas with and without ALK translocation can be applied as supplemental external positive and negative tissue control and are crucial at the validation/verification phase of the IHC methods. The ALK status of all the included positive and negative tissue controls must be confirmed by FISH in the validation process.
ALCLs will typically express a too high level of antigen and cannot be recommended as the only positive tissue control for lu-ALK.
1. Le Beau MM, Bitter MA, Larson RA, et al: The t(2;5)(p23;q35): A recurring chromosomal abnormality in Ki-1- positive anaplastic large cell lymphoma. Leukemia 1989;3: 866-870. 2. Rimokh R, Magaud JP, Berger F, et al: A translocation involving a specific breakpoint (q35) on chromosome 5 is characteristic of anaplastic large cell lymphoma (‘Ki-1 lymphoma’). Br J Haematol 1989;71: 31-36. 3. Kaneko Y, Frizzera G, Edamura S, et al: A novel translocation, t(2;5)(p23;q35), in childhood phagocytic large T-cell lymphoma mimicking malignant histiocytosis. Blood 1989;73: 806-813. 4. Bitter MA, Franklin WA, Larson RA, et al: Morphology in Ki-1(CD30)-positive non-Hodgkin’s lymphoma is correlated with clinical features and the presence of a unique chromosomal abnormality, t(2;5)(p23;q35). Am J Surg Pathol 1990;14: 305-316. 5. Mason DY, Bastard C, Rimokh R, et al: CD30-positive large cell lymphomas (‘Ki-1 lymphoma’) are associated with a chromosomal translocation involving 5q35. Br J Haematol 1990;74: 161-168. 6. Morris SW, Kirstein MN, Valentine MB, et al: Fusion of a kinase gene, ALK, to a nucleolar protein gene, NPM, in non-Hodgkin’s lymphoma. Science 1994;263: 1281-1284. 14. Duyster J, Bai RY, Morris SW: Translocations involving anaplastic lymphoma kinase (ALK). Oncogene 2001;20: 5623-5637. 11. Pulford K, Lamant L, Morris SW, et al: Detection of anaplastic lymphoma kinase (ALK) and nucleolar protein nucleophosmin (NPM)-ALK proteins in normal and neoplastic cells with the monoclonal antibody ALK1. Blood 1997;89: 1394-1404. 12. Iwahara T, Fujimoto J, Wen D, et al: Molecular characterization of ALK, a receptor tyrosine kinase expressed specifically in the nervous system. Oncogene 1997;14: 439-449. 13. Morris SW, Naeve C, Mathew P, et al: ALK, the chromosome 2 gene locus altered by the t(2;5) in non-Hodgkin’s lymphoma, encodes a novel neural receptor tyrosine kinase that is highly related to leukocyte tyrosine kinase (LTK). Oncogene 1997;14: 2175-2188. 7. Shiota M, Fujimoto J, Semba T, Satoh H, Yamamoto T, Mori S. Hyperphosphorylation of a novel 80 kDa protein-tyrosine kinase similar to Ltk in a human Ki-1 lymphoma cell line, AMS3. Oncogene. 1994;9:1567-1574. 8. Fujimoto J, Shiota M, Iwahara T, et al. Characterization of the transforming activity of p80, a hyperphosphorylated protein in a Ki-1 lymphoma cell line with chromosomal translocation t(2;5). Proc Natl Acad Sci U S A. 1996;93:4181-4186. 9. Ladanyi M. The NPM/ALK gene fusion in the pathogenesis of anaplastic large cell lymphoma. Cancer Surv 1997;30:59-75. 10. Drexler HG, Gignac SM, von Wasielewski R, Werner M, Dirks WG. Pathobiology of NPM-ALK and variant fusion genes in anaplastic large cell lymphoma and other lymphomas. Leukemia. 2000;14:1533-1559. 15. Drexler HG, Gignac SM, von Wasielewski R, Werner M, Dirks WG. Pathobiology of NPM-ALK and variant fusion genes in anaplastic large cell lymphoma and other lymphomas. Leukemia. 2000;14:1533-1559 16. Colleoni GW, Bridge JA, Garicochea B, Liu J, Filippa DA, Ladanyi M. ATIC-ALK: a novel variant ALK gene fusion in anaplastic large cell lymphoma resulting from the recurrent cryptic chromosomal inversion, inv(2)(p23q35). Am J Pathol. 2000;156:781-789 17. Meech SJ, McGavran L, Odom LF, et al. Unusual childhood extramedullary hematologic malignancy with natural killer cell properties that contains tropomyosin 4-anaplastic lymphoma kinase gene fusion. Blood. 2001;98:1209-1216 18. Tort F, Pinyol M, Pulford K, et al. Molecular characterization of a new ALK translocation involving moesin (MSN-ALK) in anaplastic large cell lymphoma. Lab Invest. 2001;81:419-426 19. Lamant L, Dastugue N, Pulford K, Delsol G, Mariamé B. A new fusion gene TPM3-ALK in anaplastic large cell lymphoma created by a (1;2) (q25;p23) translocation. Blood. 1999;93:3088-3095 20. Touriol C, Greenland C, Lamant L, et al. Further demonstration of the diversity of chromosomal changes involving 2p23 in ALK-positive lymphoma: 2 cases expressing ALK kinase fused to CLTCL (clathrin chain polypeptide-like). Blood. 2000;95:3204-3207 21. Shiota M, Fujimoto J, Takenaga M, et al. Diagnosis of t(2;5)(p23;q35)-associated Ki-1 lymphoma with immunohistochemistry. Blood. 1994;84:3648-3652. 22. Bischof D, Pulford K, Mason DY, Morris SW. Role of the nucleophosmin (NPM) portion of the non-Hodgkin's lymphoma-associated NPM-anaplastic lymphoma kinase fusion protein in oncogenesis. Mol Cell Biol. 1997;17:2312-2325. 23. Falini B, Bigerna B, Fizzotti M, et al. ALK expression defines a distinct group of T/null lymphoma ("ALK lymphoma") with a wide morphological spectrum. Am J Pathol. 1998;153:875-886. 24. Shiota M, Nakamura S, Ichinohasama R, et al. Anaplastic large cell lymphomas expressing the novel chimeric protein p80NPM/ALK: a distinct clinicopathologic entity. Blood. 1995;86:1954-1960. 25. Falini B, Pileri S, Zinzani PL, et al. ALK+ lymphoma: clinico-pathological findings and outcome. Blood. 1999;93:2697-2706. 26. Rassidakis GZ, Sarris AH, Herling M, et al. Differential expression of bcl-2 family proteins in ALK-positive and ALK-negative anaplastic large cell lymphoma of T/null-cell lineage. Am J Pathol. 2001;159:527-535. 27. Chan JK, Cheuk W, Shimizu M. Anaplastic lymphoma kinase expression in inflammatory pseudotumors. Am J Surg Pathol. 2001;25:761-768 28. Lawrence B, Perez-Atayde A, Hibbard MK, et al. TPM3-ALK and TPM4-ALK oncogenes in inflammatory myofibroblastic tumors. Am J Pathol. 2000;157:377-384. 29. Li XQ, Hisaoka M, Shi DR, Zhu XZ, Hashimoto H. Expression of anaplastic lymphoma kinase in soft tissue tumors: an immunohistochemical and molecular study of 249 cases. Hum Pathol. 2004;35:711-21. 30. Lamant L, Pulford K, Bischof D, et al. Expression of the ALK tyrosine kinase gene in neuroblastoma. Am J Pathol. 2000;156:1711-1721. 31. Delsol G, Lamant L, Mariame B, Pulford K, Dastugue N, Brousset P, Rigal-Huguet F, al Saati T, Cerretti DP, Morris SW, Mason DY. A new subtype of large B-cell lymphoma expressing the ALK kinase and lacking the 2; 5 translocation. Blood. 1997;89:1483-90.