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. An introduction to lung pathology is in the lung 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, +/-vacuole with mucin	Abundant, "dense"	Abundant r/o small cell, mucin vacuole r/i adenocarcinoma
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

Microscopic

• 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.

Image(s):

• SCC (WC).

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).