Discussion in 'NEET 2013 All india Exam' started by samuel, Nov 3, 2014.

  1. samuel

    samuel New Member

    Molecular features:
    i. Squamous cell carcinoma – shows highest frequency of TP53 mutation of all histologic types of lung carcinoma.
    Also loss of retinoblastoma (RB) tumour suppressor gene & loss of CDKN2A1
    ii. Small cell carcinoma – loss of p53, Rb in 90%, high levels of BCL – 2
    iii. Adenocarcinoma – cancers in non-smokers have EGFR mutations, but in non-smokers KRAS mutations are not present.
    i. Adenocarcinoma –
    - Mainly express thyroid transcription factor – 1
    - Mucinous adenocarcinoma spread aerogenously forming satellite tumours.
    ii. Squamous cell carcinoma –
    - Strongly associated with smoking
    - Preceded by squamous metaplasia or dysplasia
    - Both adenocarcinoma & squamous cell carcinoma remain localized longer and have better prognosis.
    iii. Small cell carcinoma –
    - No known preinvasive phase
    - Size of small cells are smaller than three times the diameter of small resting lymphocyte.
    - Cells have finely granular nuclear chromatin - Salt & pepper pattern
    - Most commonly associated with ectopic hormone production
    iv. Large cell carcinoma –
    - Undifferentiated malignant epithelial tumour that lacks the cytologic features of other forms of lung cancer.
    Site of metastasis – Adrenals (most common), Liver, Brain, Bone

    Pancoast tumours – Apical lung cancers involving lower trunk of brachial plexus and cervical sympathetic plexus. It leads to severe pain in the distribution of the ulnar nerve and Horner Syndrome on the same side of the lesion.

    Pleural tumour-
    Malignant mesothelioma
    - May arise either from the visceral or parietal pleura
    - Long latent period of 25 to 45 years
    - Most common cytogenetic abnormality is deletion of tumour suppressor gene CDKN 2A/INK4a
    This deletion is present on Ch. 9 and is helpful in diagnosis
    Mesotheliomas also arise in the peritoneum, pericardium, tunica vaginalis & genital tract.
    - Carries poor prognosis

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