Dr. Saqi: Lung cancer is the leading cause of cancer-related deaths worldwide.3 In the recent past, however, significant progress has been made in the field of lung cancer, including in the understanding of underlying pathogenesis, molecular diagnostic tests, and treatment options. In order to maximize the benefits from these advances, we need to optimize the manner in which lung cancer specimens are managed.
For patients who present at an early stage or have a resectable tumor, requirements for specimen collection and processing for molecular testing are relatively straightforward. Typically, the resected cancers provide sufficient tissue to perform the necessary molecular tests.1,2
However, obtaining sufficient tissue for molecular testing from patients who present at an advanced stage is challenging. Often these patients are not surgical candidates, and they typically undergo a minimally invasive procedure, such as a fine-needle aspiration biopsy or a core biopsy, to obtain a tissue sample and determine the appropriate management.1,2 Relative to their
Several published studies and personal experience demonstrate that molecular testing is feasible and provides results similar to those obtained from larger resected cancers.5,6 In order to ensure that sufficient quality and quantity of material is obtained, it is necessary for the pathologist to coordinate efforts with clinicians obtaining the samples to ensure appropriate triage and processing.
So there are several steps that can be undertaken to maximize the results. First, let us address the core biopsies. These are often obtained under CT guidance, and given the risk of pneumothorax and hemoptysis,
The question is, how many cores are needed to make a histological diagnosis, and, if necessary, immunohistochemical and molecular diagnoses? This really depends on the content of the core. In some institutions, rapid onsite evaluation by a cytopathologist is performed. Touch preparations are performed by a cytologist to make a preliminary assessment. This is somewhat controversial, and not always available.
So the clinician obtaining the biopsy can play a significant role by performing a gross examination of the biopsy. It is important to see if the core represents a solid piece of
Also, the greater the number of cores, the greater the likelihood of having sufficient tissue for ancillary testing. And currently, there are no guidelines dictating the minimal number of cores. However, if it's feasible and accessible without significant risk to the patient, personal experience has demonstrated that a minimum of three
So what about the protocol for fine-needle–aspiration specimens? This is slightly different than that of core biopsies.
If pathology department resources allow, having rapid onsite evaluation of the aspirate by an experienced cytologist is invaluable.9 The cytologist can provide a diagnosis and request additional samples in cases of scant specimens. But most importantly, either in the presence or absence of a cytopathologist, it is important to allocate material for ancillary testing. This means not making too many or large smears or smears of clots, which leads to poor utilization of the specimen. And when making a smear, small, tiny, tan-white particles should be selected for the smears, and the remainder should be placed in fixative such as formalin or alcohol for cell block preparation. A dedicated pass for cell block also has a greater likelihood of yielding a sufficient specimen. And as with the cores, requesting blank slides up front minimizes loss of tissue from trimming the cell block with subsequent requests for additional slides.
Also, a first-time diagnosis in patients with advanced lung cancer is sometimes rendered on pleural effusions.1 If there is sufficient volume of specimen, a cell block should be made from these samples, as well. Especially in patients who may be unable to tolerate another procedure, cell blocks can provide a source of tissue for necessary ancillary testing.