Rural Emergency Medicine

Hi and welcome to the new pathology segment. Each week I hope to follow up on a different group of diseases & disorders (basically working my way through Robbin's Pathologic Basis of Disease). I shall include some short notes concerning the most relevant features of the disease, as well as appropriate multimedia resources.

This a trial to see what works & what doesn't. Your feedback would be greatly appreciated either via, twitter to @IVLine or by commenting below.

First up we will be taking a look at pathology that occurs within the Respiratory System, and more specifically Pulmonary Tumours. If you're short on time and what to get the general gist, of Pulmonary Tumours (aka lung cancer), @Eleytherius has summed up the pathology in a tweet.

While pathology is an important component of medicine, it is useful to remember how to conduct a respiratory clinical exam to assist in diagnosis.

Basic Lung Anatomy & Histology
As always it's good to refresh basic lung anatomy, both at a macroscopic and microscopic level.

Adapted from ADAM & Wikipedia

Structure of Lower Respiratory Tract by Aaron Sparshott

For further reading, Blue Histology by UWA, provides some more in depth histology of normal respiratory tissue. The video below quickly runs through the normal lung histopathology.

Normal Lung Histopathology

Bronchogenic Carcinomas

Small Cell Carcinoma (SCLC)
  • Highly Malignant Tumour
  • Cells are small, with scant cytoplasm, ill-defined borders, finely granular chromatin (salt & pepper pattern) and absent or inconspicious nucleoli.
  • High mitotic count and often extensive necrosis.
  • Typically not graded as all SCLC are considered High Grade.
  • Very strong relationship with smoking.
  • Often lead to paraneoplastic syndromes.
  • Limited Treatment options: Small cell tumours are nearly always disseminated at presentation.

Imaging Case

Non-small Cell Carcinoma (NSCLC)
Non-small Cell Carcinoma includes a number of sub-types. These tumours can be operated on. TNM staging is used for these tumours. A list of common tumours in this group are listed below.
  • Squamous Cell Carcinoma
  • Adenocarcinoma
  • Large Cell Carcinoma

    Squamous Cell Carcinoma
    • Most commonly found in men and correlated with smoking
    • Pathology: more differentiated, more cytoplasm, keratin whorls
    • Preceded by squamous metaplasia or dyplasia in bronchial epithelium (Asymptomatic)
    • Transforms to carcinoma in situ
    • Tumour mass obstruct lumen → distal atelectasis and infection (Symptomatic)
    • Grading is based on the amount of keratin & cytoplasm

    • Adenocarcinoma is the most common type of lung cancer, making up 30-40% of all cases.
    • Glandular differentiation by tumour cells and 80% of those cells produce mucin. The majority of those cells are also positive to thyroid transcription factor-1 (TTF-1).
    • Not as strongly associated with a smoking history as compared to Squamous or Small Cell Carcinomas
    • Adenocarcinoma in situ - called bronchoalveolar carcinoma
    • Early and distant metastases

    Large Cell Carcinoma
    • Can be a neuroendocrine carcinoma. Probably represents undifferentiated SCC and adenocarcinomas
    • Large nuclei, prominent nucleoli
    • Variation in size and shape
    • Nuclei normally do not touch due to more cytoplasm.
    • Moderate amount of cytoplasm
    • Several variants of LCLC, including (a) basaloid, (b) clear cell, (c) lymphoepithelioma-like, (d) rhabdoid phenotype, and (e) large-cell neuroendocrine carcinoma.
    • Early and distant metastases, sometimes cavitating

      LOWER RESPIRATORY TRACT: LARGE CELL CARCINOMA by The Armed Forces Institute of Pathology
      The corresponding surgical resection shows neoplastic cells with abundant pale eosinophilic cytoplasm and a surrounding infiltrate of inflammatory cells which can also be seen among the tumor cells in the fine needle aspirate specimen.

      Large cell neuroendocrine carcinoma by Pulmonary Pathology 
      This tumor exhibits an insular growth pattern with gland-like structures and peripheral palisading of nuclei. High mitotic activity can be seen even at this relatively low magnification. In addition to "neuroendocrine morphology" mitotic activity of 11 or more/10 high power fields is currently required to diagnose large cell neuroendocrine carcinoma.

      LOWER RESPIRATORY TRACT: LARGE CELL CARCINOMA by The Armed Forces Institute of Pathology
      This large cell carcinoma at autopsy shows a large multilobulated tumor adjacent to the hilum. A metastatically involved lymph node is present next to the bronchus.
      Clinical Pearl: 2/3 of Primary Lung Cancer is found in the upper lungs, whilst 2/3 of metastases are found in the lower lung (due to hematogenous spread).

      Videos are thanks to  . Material is sourced from my notes from pathology tutorials at UQ, and Robbin's Pathologic Basis of Disease. References for images are underneath the image.

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