In many cases we are able to make a correct diagnosis based on cytology alone. However there are several important points in the lung cancer:

1. Sometimes there is a need of immunohistochemistry (IHC) to discriminate between adenocarcinoma and squamous cellcarcinoma so we should have an appropriate material (cell block is good). Some other tumors need IHC as well (small cell carcinoma for example)

2. In the case of adenocarcinoma the material available for mutational analysis is needed.

3. If you have touch print it means you have a tissue sample as well. Possibly you mentioned FNA?

Thank you , but do you mean that FNA is equivalent to slide touch or less sensitive? thanks again yours,

Hamdy Elayouty

I don't have an universal answer. If you have a touch it means you have both tissue sample and imprint taken from this sample i.e. both histological and cytological material whereas the FNA is cytology alone. However several FNA needle passes may be done in different directions so it's sensitivity could be higher than that of core biopsy, and the cell block could be (I would say should be) prepared as well. The question is whether your reference laboratory is able (both practically and legally) to perform the mutational analysis in the FNA material (cell blocks I mean) in the cases it is needed.

Sincerely,

Alexander Shtabsky

I agree with Alexander that as you mentioned from lung tissue you can make tissue imprint only when you have biopsy sample. In this setting, the imprint may be useful in making an early diagnosis, which in most cases may well agree with histological diagnoses. However, the diagnosis may later be confirmed by histopathology.

In all cases we are able to make a correct diagnosis based on cytology alone. In the lung cancer:

1. The use of immunohistochemistry (IHC) on slides and/or cell block .

2. Mutational analysis in adenocarcinoma.

we are able to make a diagnosis in cytology long time with diagnostic accuracy. The slides are prepared by us and when necessary ask the radiologist repeat sampling for tests of molecular biology and / or imuno cytochemistry. However, the diagnostic slide with the collaboration of another university institute with the technique of laser cells are extracted for research of EGFR.

Yes but it needs a lot of experience and has the advantage of been cheap and quick and can be repeated

There are many benefits to lung cytology specimens, particularly those obtained by FNA. Based on the 2015 WHO criteria for the diagnosis of lung tumors, immunostaining is increasingly critical for the accurate diagnosis of non-small cell lung carcinoma. When an FNA is performed, the needle can be rinsed into a solution after expressing the aspirate onto a slide. At the end of all FNA passes, this material can be spun down to make a cell block. This cell block can then be used to perform immunostaining and to perform molecular testing. With new targeted therapy being developed for several different lung cancer mutational pathways, obtaining material for the purpose of molecular testing is increasingly important. At our institution, we perform a basic molecular panel for all new lung adenocarcinoma diagnoses. No longer is it enough to diagnose the tumor. FNA, for example by EBUS, offers a minimally invasive technique to obtain material for diagnosis and for molecular work-up.

Do you perform FISH for ALK in the smear as well? I know that it is done in several centers but it seems to me much more challenging than PCR (for EGFR, for example).

No. We perform ALK gene rearrangements by FISH on paraffin-embedded tissue only. In this context, it is most commonly performed on cell block material; however, we have just undergone clinical validation for ALK immunostaining, which is interesting because it drastically improves turn around time. 

So, if you have a negative IHC it is negative and for positive you proceed to FISH, correct?

One more question: what fixative do you use for cell blocks (4% formalin, formalin-ethanol or something else)?

We are still working on our current testing algorithm but that is how we are proceeding at this point.

For cell block preps, we use 10% neutral buffered formalin.

Thank you for the answers. I just used a wrong term (10% formalin = 4% formaldehyde).