Episode 024: Lung Cancer Series, Pt. 2: Fundamentals of histology and staging

Lung cancer is one of the most commonly diagnosed type of cancer and so it is fitting that we start the first of our disease-specific oncology series with this diagnosis. This week, we go through the fundamentals of histology and staging.

If you have not done so, we highly recommend you listen to last week’s episode first!

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Lung Cancer Histology and Staging

• Workup for a nodule that is concerning:

  • Ensure there is a dedicated CT scan of the chest to evaluate

  • Try to obtain old imaging; the rate of change is important

  • Can get PET, but even if a lesion if not FDG-avid, but growing quickly we should consider biopsy anyway

  • Referral to pulmonary medicine, who can assist with biopsy and also regional lymph node evaluation (important – more below)

  • PFTs are often ordered because it provides information about lung function in anticipation of possible surgery for treatment

• Lung Cancer Histology:

  • Non-small cell lung cancer (NSCLC)

    • Umbrella term for a variety of cancers

    • Increased risk in smokers

    • More common types:

      • Adenocarcinoma (~50% of all lung cancers)

        • Most common overall; cancer of the mucus producing cells

        • IHC: TTF-1, NapsinA, CK7 positive

      • Squamous Cell Carcinoma (22.7%)

        • More often seen in patients with a smoking history

        • IHC: p63 positive and cytokeratin pearls

    • Remaining ~15% are the other types of lung cancer / mixed histologies

  • Small cell lung cancer (SCLC)

    • Neuroendocrine tumor with very different pathology

    • Much more aggressive than NSCLC

    • Oncologic emergency

    • IHC: Chromogranin and synaptophysin positive

  • IHC pearls: TTF-1 usually means lung cancer (but can be negative in squamous cell lung cancer). This will be important in the future (we promise :])

• Staging for NSCLC:

  • Nodal evaluation: lymph node evaluation is part of the workup for NSCLC

    • Single digit = central/mediastinal nodes (higher risk)

    • Double digit = peripheral/hilar/intrapulmonary lymph nodes (lower risk)

    • “R” vs. “L” is direction

  • Pearl: Why is this important? If there is nodal involvement, systemic therapy is going to be necessary

Nodal stations. Image source: http://dx.doi.org/10.1016/j.ccm.2013.04.008

Putting it all together:

• T: Tumor size

  • T1-4

• N: Nodal involvement

  • N0: no nodal involvement

  • N1: Nodes closest to the primary tumor (double digits)

    • Ipsilateral peribronchial, hilar, intrapulmonary

  • N2: Further away (single digit)

    • Ipsilateral mediastinal and/or subcarinal LN

  • N3: Contralateral any node or supraclavicular LN

• M: Metastasis – in lung cancer, patients with certain patterns of metastatic disease are still curable!

  • M0: no mets

  • M1a: Contralateral lobe, pleural effusion or pericardial effusion à these are generally still curable!

  • M1b: single site of metastatic disease à these are generally still curable!

  • M1c: multiple sites of metastatic disease à these are generally not curable

Staging for lung cancer. Image Source: https://doi.org/10.1016/j.jtcvs.2017.08.138

• Staging for SCLC:

  • Limited stage - meaning it can fit in “one radiation field”

  • Extensive stage - does not fit in “one radiation field”

• Once lung cancer is diagnosed:

  • Go to NCCN to learn the flow of ongoing management

  • Complete staging (if not already done):

    • CT C/A/P (don’t necessarily need if a PET scan is done)

    • PET Scan

    • MRI brain à in general this is needed, but there are some exception to this (see NCCN)

    • Referral to pulmonary for nodal evaluation

References:

NCCN.org

https://doi-org.proxy.library.vanderbilt.edu/10.1016/j.semcancer.2017.11.019-Article about IHC markers for lung cancer

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