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

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

The Fellow on Call: The Heme/Onc Podcast

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