Fig. 1Break-apart fluorescence in situ hybridization (FISH) patterns. Representative FISH images of anaplastic lymphoma kinase (ALK)-negative (A) and ALK-rearranged tumors (B, C) are demonstrated. Tumors are considered ALK-positive when green and red signals are separated by at least two signal diameters (B) or a single red signal without a corresponding green signal, in addition to fused and/or break-apart signals (C).
Fig. 2Anaplastic lymphoma kinase protein expression by immunohistochemistry with a 0-3 intensity-based scoring system. Representative images of score 3 (A), 2 (B), 1 (C), and 0 (D) are displayed.
Fig. 3Diagnostic algorithm for molecular testing of small biopsy or cytological specimens in non-small cell lung cancer patients. LCNEC, large cell neuroendocrine carcinoma; SqCC, squamous cell carcinoma; ADC, adenocarcinoma; NSCLC, non-small cell lung carcinoma; NOS, not otherwise specified; ASC, adenosquamous carcinoma; IHC, immunohistochemistry; EGFR, epidermal growth factor receptor; ALK, anaplastic lymphoma kinase; FISH, fluorescence in situ hybridization.
Table 1.Summary of ALK testing guideline recommendations
|
Recommendation |
Patient eligibility |
Histologic type is the most important factor: patients diagnosed with adenocarcinoma, large cell carcinoma or non-small cell carcinoma with adenocarcinoma component should be tested for ALK rearrangement. |
Clinical criteria might be considered, when adenocarcinoma component cannot be completely excluded. |
Specimen type |
Histological and cytological specimens are both acceptable. |
Either primary tumors or metastatic lesions are equally suitable. |
In cases with multiple, synchronous primary lung adenocarcinomas, each tumor may be tested. |
Sample selection |
A minimum of 50-100 assessable tumor cells are required for ALK FISH test. |
ALK IHC can be performed as long as there are at least a few clusters of viable tumor cells. |
Sample processing |
Fixative: 10% neutral-buffered formalin, immediately after the sample is removed from the patient. |
Fixation time: from 6 to 48 hours. |
Avoid decalcified tissue. |
Routine preparation for cytology is acceptable, if fully validated. |
Diagnostic method |
FISH is a companion diagnostic test for detection of ALK rearrangement. |
IHC can be a potential screening method with high sensitive detection method. |
RT-PCR is highly sensitive but not recommended as a first-line diagnostic method for determining ALK fusion status. |
The pathologist should consider the pros and cons of each method and combination of more than one technique may be useful in equivocal cases. |
Reporting format |
Patients and sample information, type of detection method, results of the test, comments. |