Respiratory System II Pathology Flashcards

WHO Classification of Tumours 5th Edition

  • Thoracic Tumours
  • International Histological Classification of Tumours No. 21

ICD-O Coding of Lung Tumours

  • Lists various epithelial tumours, adenomas, adenocarcinomas, squamous cell carcinomas, and other tumour types with their corresponding ICD-O codes.
  • Includes precursor lesions, salivary gland-type tumours and lung neuroendocrine neoplasms
  • Covers tumours of ectopic tissues, mesenchymal tumours specific to the lung and haematolymphoid tumours.

Benign Epithelial Tumours

  • Papillomas:
    • Squamous cell papilloma, NOS (8052/0)
    • Squamous cell papilloma, inverted (8053/0)
    • Glandular papilloma (8260/0)
    • Mixed squamous cell and glandular papilloma (8560/0)
  • Adenomas:
    • Sclerosing pneumocytoma (8832/0)
    • Alveolar adenoma (8251/0)
    • Papillary adenoma (8260/0)
    • Bronchiolar adenoma / ciliated muconodular papillary tumour (8140/0)
    • Mucinous cystadenoma (8470/0)
    • Mucous gland adenoma (8480/0)

Squamous Cell Papilloma

  • Benign tumor arising from epithelial surface, grows outward.
  • Occurs in large bronchi, often with tracheal or laryngeal lesions.
  • Presentation: endobronchial exophytic growth.
  • Typically found in middle-aged male smokers.
  • Associated with HPV 6 and HPV 11; high-risk HPV may be seen in cases associated with carcinoma.
  • Clinical presentation: hemoptysis, recurrent pneumonia, asthma-like symptoms, dry cough.

Morphology Gross description

  • Tan-white, friable, pedunculated / polypoid, smooth to verrucoid, glistening.
  • Wart-like, cauliflower-like.
  • Less than a few centimeters in size.

Microscopic Description

  • Exophytic, papillary lesion with arborizing fibrovascular cores lined by keratinizing or nonkeratinizing mature squamous epithelium.
  • Rarely inverted pattern.
  • Lesion may grow into adjacent alveolar spaces.
  • May contain areas lined by ciliated or non-ciliated columnar cells with cuboidal cells or mucin-filled cells (mixed squamous and glandular papilloma).
  • May exhibit viral cytopathic effect: enlarged hyperchromatic nuclei, nuclear wrinkling, polychromasia, binucleate forms, perinuclear halos.
  • Mild to moderate stromal inflammation which may be related to airway obstruction.
  • No mitoses, no necrosis

Lung Cancer - Key Facts

  • Leading cause of cancer-related deaths worldwide.
  • Smoking is the leading cause (approximately 85% of cases).
  • Often diagnosed at advanced stages.
  • Screening high-risk individuals can improve survival rates.
  • Primary prevention can reduce incidence.

Types of Lung Cancer

  • Small Cell Lung Cancer (SCLC)
    • Small Cell Carcinoma (SCC)
    • Combined Small Cell Carcinoma (CSCC)
  • Non-Small Cell Lung Cancer (NSCLC)
    • Adenocarcinoma
    • Squamous Cell Carcinoma (SCC)
    • Large Cell Carcinoma (LCC)

Squamous Cell Carcinoma

  • Malignant tumor from epithelial cells with squamous differentiation.
  • Presence of keratinization or intercellular bridges.
  • Strong association with tobacco smoking (80% of men and 90% of women).
  • Primarily in patients over 50 years of age.
  • 85% of primary lung cancers are non-small cell carcinomas, and squamous cell makes up 30% of these cases.

Sites

  • Can present in any site of the lungs or bronchus but is more commonly central
  • Mediastinal lymph nodes are the primary site of metastasis
  • Hematogenous spread to distant organs:
    1. Bone
    2. Liver

Pathophysiology

  • Squamous cells lining the respiratory tract transformed from carcinogen exposure, most frequently smoking.
  • Occupational heavy metal exposure

Clinical Features

  • Wide range of nonspecific pulmonary symptoms:
    • Cough
    • Chest pain
    • Shortness of breath
    • Hemoptysis
    • Wheezing
    • Weight loss
    • Recurrent infections
    • Loss of appetite and fatigue

Gross Description

  • Cavitary mass with white, smooth cut surfaces that frequently contain hemorrhage and necrosis.
  • Mass is more often central than peripheral and may be within the bronchus.

Microscopic Description

  • Range from well differentiated squamous cell neoplasms showing keratin pearls and intercellular bridges to poorly differentiated neoplasms exhibiting only minimal squamous cell features.
  • Poorly differentiated squamous cell carcinoma exhibits severe cellular and nuclear atypia, abundant mitosis and often requires IHC studies to differentiate from other poorly differentiated lesions.

Development of SCC

  • Normal epithelium → Hyperplasia → Squamous metaplasia → Dysplasia → Carcinoma in situ → Invasive carcinoma

Characteristics

  • Keratinization
  • Intercellular bridges
  • Abundant eosinophilic cytoplasm

Alveolar Adenoma

  • Well circumscribed tumor consisting of cystic spaces lined by a single layer of type II pneumocytes overlying a spindle cell stroma.
  • Solitary and peripheral tumors.
  • Incidental diagnosis.
  • Rare tumors
  • Slightly female preponderance
  • 39-74 y

Gross Description

  • Size: 7-60 mm
  • Well demarcated
  • Smooth, lobulated multicystic pale yellow to tan surface cut.

Microscopic Description

  • Cystic spaces filled with eosinophilic granular material.
  • Lined by cytologically bland flattened to cuboidal epithelial cells (pneumocytes type II)
  • Myxoid or collagenous stroma.

Lung Adenocarcinoma

  • Most prevalent non-small cell lung carcinoma.
  • Female > Male
  • Most common type of lung cancer in male nonsmokers
  • African Americans > Caucasians
  • Age 60 - 70

Sites

  • Upper lobe > lower lobe
  • Peripheral > central
  • Metastasis: brain (often only site) > bone > liver > adrenal
  • Risk for brain metastasis increases with tumor size and lymph node stage

Pathophysiology

  • Toxic cellular exposures → genetic mutations → proliferation of endobronchial cells
  • Genetic events

Etiology

  • Smoking is the greatest risk factor, including secondhand smoke
  • Radon from soil, usually in residential areas
  • Asbestos exposure

Clinical Features

  • Cough (productive if mucinous adenocarcinoma), hemoptysis, dyspnea, weight loss, chest pain.
  • Paraneoplastic / endocrine syndromes.
  • Paraneoplastic syndromes are disorders that are triggered by an altered immune system response to a neoplasm. / Clinical syndromes involving nonmetastatic systemic effects that accompany malignant disease.

Gross Description

  • Tan-white cut surface
  • May have central area of scar or necrosis
  • Usually well-defined but nonencapsulated

Microscopic Description

  • 5 main histologic patterns:
    • Lepidic: type II pneumocytes and club cells proliferate to line alveolar walls; lacks architectural complexity; no lymphovascular or perineural invasion
    • Acinar: gland forming; round / oval glands invading the stroma (usually fibrous)
    • Papillary: malignant cuboidal / columnar cells replace alveolar lining; contains fibrovascular cores.
    • Micropapillary: ill-defined projection / tufting that lacks fibrovascular cores
    • Solid: sheets of neoplastic cells