Pulmonary cytopathology

Pulmonary cytopathology is a subset of cytopathology.

This article deals only with pulmonary cytopathology (FNAs, sputum samples). An introduction to cytopathology is in the cytopathology article.

Normal

• Cells with cilia = good.
• Cells with "terminal bar" (apical red band-like region associated with cilia) = good.

Specimens

1. Bronchial brushings.
2. Bronchial washing (contain airway cells).
3. Bronchoalveolar lavage (BAL).
4. Endobronchial ultrasongraphic transbronchial needle aspiration (EBUS-TNA).

Adequacy

• Want to see pulmonary macrophages (large cells with bubbly green/brown cytoplasm, eccentric reniform nucleus).
  • Ciliated cells may be from the nasopharynx - not proof of lung parenchymal tissue.

There is no generally accepted standard for pulmonary specimens. An in-house standard is:

• Sputum: >= 10 pulmonary macrophages.

Pulmonary hamartoma

Histology:

• No cytologic features of malignancy.
• Fat.

Non-specific inflammation

• A very common finding in BALs.

Types:

• Eosinophilia
  • If you notice eosinophils... you probably have eosinophilia.
    • One in several HPFs (40x obj. with 22 mm eye piece) is enough.
• Acute - neutrophils.
  • ~10/HPF (40xo 22mm ep).
• Chronic - lymphocytes + occ. plasma cells.
  • ~5 small lymphocytes/HPF (40xo 22 mm ep).
• Mixed acute & chronic inflammation.

Infection

If you see lotsa lymphocytes think tumour.

Pneumocystic carinii pneumonia (PCP)

Features:

• Casts of frothy material/large proteinaceous debris - approximately the size of an alveolus.

Aspergillosis

Features:

• Hyphae... branching at 45 degrees.

Image:

• Aspergillosis (WC).

Zygomycosis

• AKA mucormycosis.

Features:

• Hyphae... with variable width.

Image:

• Zygomycosis (WC).

Crytococcus

Features:

• Prominent (i.e. thick polysaccharide) capsule.
  • Seen well on Pap stain... harder to see on rapid Romanowsky stain.
• Spherical - 5-15 micrometres.

Image:

• Cryptococcus (WC).

DDx:

• Bastomycosis.
  • Doesn't have thick capsule
  • Has broad based budding.
• Coccidioidomycosis - larger (20-60 micrometers).

Cancer

Approaches to lung cancer

Lung cancer in a table

	Small cell carcinoma	Adenocarcinoma	Squamous cell carcinoma	Value
Cellular cohesion	Single cells/stripped nuclei common	Cohesive	Cohesive	Cohesive (only) suggests NSCLC
Nuclear moulding	Present	Absent	Absent	R/i & r/o: small cell carcinoma and carcinoid
Small nucleoli (difficult to see on Field stain)	Multiple pseudo-nucleoli may be seen in occ. cells	Many be present	Often present	Weak discriminative valuable
Large nucleoli	Never	Present	Rarely	R/i adenocarcinoma; should prompt consideration of melanoma briefly
Location of nucleus	Eccentric	Eccentric	Central	Useful for SCC vs. adenocarcinoma
Cytoplasm	Scant	Abundant, bubbly	Abundant, "dense"	Abundant r/o small cell
Streaming	Absent	Absent	Present - "stretched yeast dough"	R/i squmaous (weak)
Keratin (difficult to see on Field stain)	Absent	Absent	Present	Present r/i squamous (strong)

Criteria list

Neuroendocrine tumours - look for:

1. Nuclear moulding (not seen in NSCLC).
2. Singular bare nuclei/single cells - often very abundant in small cell lung carcinoma (SCLC).
   • Size ~2X neutrophil (PMN) - SCLC is large relative to most haematologic cancers (which are approx. the size of a PMN)... small in relation to other carcinoma.
3. Stippled chromatin.
4. Negatives: Abundant cytoplasm - virtually excludes SCLC.
5. Carcinoid vs. atypical carcinoid vs. SCLC (list from good to bad) - degree of nuclear atypia, presence of necrosis and smoking history.
   • One should never sign-out small cell carcinoma without looking at the history.

Adenocarcinoma:

1. Nucleolus.
   • Good ones are visible with 10X objective (excludes SCLC).
   • Look for subtle large ones - at higher power.
   • Neuroendocrine tumours occasionally may appear to have nucleoli - one should see good nucleoli in 3-4 cells in one field.
2. Abundant cytoplasm - virtually excludes small cell carcinoma.
3. Vacuoles with mucin (pink discolouration) - virtually diagnostic, though only seen occasionally.
4. Eccentric nucleus.
5. Negatives: NO moulding.
   • Important if no nucleolus obvious.

Squamous cell carcinoma:

1. Small nucleolus - not visible at 10X.
2. Coarse chromatin.
3. "Streaming" - think stringy yeast dough.
4. Keratin (orange) - on Pap stain.

Adenocarcinoma

• Most common type of lung cancer.

Cytology

Features:

• Nucleolus.
  • Good ones are visible with 10X objective (virtually excludes SCLC).
  • Look for subtle large ones - at higher power.
• Abundant cytoplasm - virtually excludes small cell carcinoma.
• Vacuoles with mucin (pink discolouration) - virtually diagnostic.
• Eccentric nucleus.
• Negatives: NO moulding.
  • Important if no nucleolus visible.

Notes:

• May be subtle, i.e. have minimal cytologic changes.

DDx:

• Benign mesothelium (also sheets of cells).
• Atypical adenomatous hyperplasia (AAH) - thought to be the precursor to adenocarcinoma.
  • AAH has a size criterion, ergo not really possible to diagnose on cytopathology specimen.

Neuroendocrine tumours

• This is a group of tumours that has benign (e.g. carcinoid tumour of the lung) to malignant (e.g. small cell lung carcinoma) behaviour.

The grouping can be divided into four types:

• Small cell carcinoma.
• Large cell neuroendocrine carcinoma.
• Typical carcinoid.
• Atypical carcinoid.

Cytologic features useful for differentiation:

• Small cell carcinoma: necrosis, scant cytoplasm, mitoses.
• Typical carcinoid: often more cytoplasm, no necrosis, low mitotic rate (MIB-1: scant staining).
• Atypical carcinoid: higher mitotic rate/MIB-1 than typical carcinoid, no necrosis.

Notes:

• Large cell and small cell tumours behave in a similar fashion; large cell can be considered a morphological variant of small cell.
• 9/10 of carcinoids are typical and usually have a good prognosis, i.e. do not metastasize.
  • Central location (vis-a-vis peripheral location) tends favours typical carcinoid over atypical carcinoid.

Small cell lung carcinoma

• Is the most easy lung cancer to miss, as one is usually looking for large cells.

Histology:

• Morphologic features of malignancy:
  • Irregular nuclear membrane.
  • Chromatin clumping.
  • Marked nuclear size variation.
• Bare nuclei common - very useful if present.
• Nuclear moulding - key feature.
• Stippled chromatin - key feature.
• Small cells ~ 2x RBC.
• Scant cytoplasm - so scant it often near impossible to see.

Notes:

• The Azzopardi phenomenon (smudging of nuclei) is not present on cytology specimens - it is processing artifact.
• Small cell carcinoma should not be diagnosed without a clinical history; if there is no smoking history... think about the possibility of carcinoid and atypical carcinoid.
• Small cell leukemias may mimic small cell carcinoma; difference: leukemias typically have smaller cells (~size of RBC vs. ~2x of RBC), and lymphoglandular bodies.

Image:

• Small cell carcinoma showing nuclear moulding (WC).

Squamous cell carcinoma

Histology:

• Mix of spindle cells/epithelioid cells, present in clusters, +/-small number of single cells.
• Keratinization:
  • Orange/red staining on Pap stain.
    • Poorly differentiated SCC = not orange/red.
  • "Intense" (blue) staining of cells on rapid Romanowsky + pyknotic (small shriveled) nucleus.
• "Dense" appearing cytoplasm.
  • +/-Laminae (layers)/lines in the cytoplasm.
• Nuclear features of malignancy (required for diagnosis):
  • Irregular nuclear membrane, e.g. notches, sharp discontinuities.
  • Nuclear hyperchromasia - "jet-black" nuclei on Pap stain key feature.
  • Increased NC ratio.
  • Variation of nuclear size from cell-to-cell.

Notes:

• One should see abnormal squamous cells to call it SCC.
  • The default diagnosis is usually adenocarcinoma.
• Poorly differentiated SCC may look like adenocarcinoma.

Malignant melanoma

Classic features:

1. Loosely cohesive cells and single cells.
2. Mixure of epithelioid cells and spindle cells.
3. Malignant cells have:
   • Prominent red nucleolus.
   • Pigmented cytoplasm - key feature (often not pigmented).
   • Pigment may only be present in macrophages
   • Occasional large binucleated cells (bug-eyed monster cell).
     • Nuclei are often at opposite poles of the cell, i.e. the nuclei are as far apart as possible ("divorce cells").
   • Intranuclear inclusions.
4. Pigmented macrophages (useful feature - but less specific for melanoma than pigment in malignant looking cells).

Notes:

1. Large nucleolus - may Vaguely resemble adenocarcinoma.
   • Prominent red nucleolus common in: serous carcinoma.
2. The classic appearance of melanoma without pigment is closest to adenocarcinoma (which may have red nucleoli, large cells, abundant cytoplasm, occasional binucleation).
   • Differentiating morphologic features: adenocarcinoma - 3-D clusters of cells, no spindle-shaped cells.
3. Bug-eyed monster cells - may vaguely resemble a Reed-Sternberg cell (RSC) - diagnostic of Hodgkin's lymphoma (HL).
   • RSCs do not have the granular cytoplasm typical of melanoma.
   • Nuclei usually adjacent, i.e. not at opposite poles of the cell.
   • Background of melanoma different than HL.

Images:

• Bug-eyed monster cell in melanoma - Field stain (WC).

See also

• Cytopathology.
• Basics.
• Lung.
• Lung cancer.

External links

• Respiratory cytopathology (Australian Society).