Head and neck cytopathology

Head and neck cytopathology is a small part of cytopathology. Non-cytopathology head & neck pathology is dealt with in the head and neck pathology article.

Thyroid cytopathology is dealt with in the thyroid cytopathology article. An introduction to cytopathology is in the cytopathology article.

Normal

Depends on the structure that is needled.

Parotid:

• Acini - small globoid clusters.
  • Separated by adipose tissue.
• Granular cytoplasm.
• Nucleus:
  • Dispersed chromatin.
  • Indistinct nucleolus.
• Low NC ratio cells.

Sticky lymphoid tissue:

• Irregular globs of tissue with small cells.

Salivary gland tumours - summary

Benign

Diagnosis	Architecture	Cytoplasm	Nucleus	Main DDx	Used to diff. from main DDx	Image
Pleomorphic adenoma	Fluffy fibromyxoid material & cells and single (plasmacytoid-like) myoepithelial cells	?	Myoepithelial cells - plasmacytoid appearance	DDx (?)	?	Pleomorphic adenoma (WC)
Warthin tumour (papillary cystadenoma lymphomatosum)	Sheets of uniformly spaced oncocytes, lymphocytes, necrotic debris	Oncocytes (abundant, granular, eosinophilic tinge), well-defined cell borders	Oncocytes have nucleolus	Acinic cell carcinoma (AcCC), oncocytoma	AcCC: irregular spaced cells, lack well-defined cell borders	Warthin tumour high mag (WC), Warthin tumour intermed mag (WC)

Malignant

Diagnosis	Architecture	Cytoplasm	Nucleus	Main DDx	Used to diff. from main DDx	Image
Mucoepidermoid carcinoma	Clumps of cells	Abundant whispy cytoplasm	Small oval nucleus, +/-distinct nucleolus	Mucocele ?	Nuclear atypia	Mucoepidermoid carcinoma (WC)
Adenoid cystic carcinoma (AdCC)	Circular islands of abundant very small cells	Scant cytoplasm	Small nucleus - may have carrot shape	AcCC	Basement membrane material - PAS-D+ve	Adenoid cystic carcinoma (WC)
Acinic cell carcinoma (AcCC)	3-D clusters of small cells	Abundant orangeophilic granular cytoplasm	Stippled chromatin	Warthin tumour	AcCC missing lymphocytic background; irreg. spacing of cells	Acinic cell carcinoma (WC)

Pleomorphic adenoma

General:

• Common benign tumour.
• Abbreviated PA.

Cytology

Features (MEC):

1. Myoepithelial cells.
   • Plasmacytoid-like cells.
     • Single cells (very common) or small clumps - oval shape.
2. Epithelial cells.
3. Chondromyxoid stroma.
   • Whispy/fluffy groups of spindle cells that overlap (fibromyxoid tissue) - blue-ish.

Image:

• Pleomorphic adenoma (WC).

DDx:

• Adenoid cystic carcinoma.
  • Big circular globs (cysts) - common in AdCC.

Warthin tumour

• AKA papillary cystadenoma lymphomatosum.

Histology

Features:

• Oncocytes.
  • • Well-defined cell border.
    • Granular cytoplasm.
    • Nucleoli.
  • Oncocytes are often associated with mast cells, i.e. on "top of" oncocytes.
    • Mast cells: very granular dark staining cytoplasm (on smears).
• Lymphocytes.
• Necrotic material (cyst contents).

Images:

• Warthin tumour high mag (WC).
• Warthin tumour intermed mag (WC).
• Warthin tumour - surgical excision specimen (WC).

DDx:

• Acinic cell carcinoma.
  • Spacing of tumour in AcCC is more irregular and appear more crowded.
  • The cell borders in AcCC is less obvious.
• Oncocytoma
  • Oncocytoma (vis-a-vis Warthin tumour) has more cells, more cytoplasm, more granularity of cytoplasm, more complex architecture.

Oncocytoma

• May be confused with Warthin tumour.

Features:

• Oncocytes.
  • • Well-defined cell border.
    • Granular cytoplasm.
    • Nucleoli.

Vis-a-vis Warthin tumour:

• Oncocytoma has:
  • More cells,
  • More cytoplasm,
  • More granularity of cytoplasm,
  • More complex architecture.

Mucoepidermoid carcinoma

Main article: Mucoepidermoid carcinoma

Features:

• Sheets of cells.
• Cells have a small oval nucleus with nucleolus.
• Fluffy cytoplasm with a pink tinge (on Pap stain) - key feature.
  • Cytoplasm not seen in 3-D clusters - look for single layer of cells.
  • Cell borders are often distinct.

Images:

• Mucoepidermoid carcinoma (WC).
• Mucoepidermoid carcinoma - very high mag. (WC).
• Mucoepidermoid carcinoma - not a very good image (WC).

Acinic cell carcinoma

Features:

• Abundant granular cytoplasm.
• Stippled chromatin.
• +/-Nucleolus.

Notes:

• Often accompanied by stripped nuclei; may mimic lymphocytes (may lead to confusion with Warthin tumour).
• Lack:
  • Adipocytes between acini (differentiates from normal).
  • Ductal structures (differentiates from normal).

Image:

• Acinic cell carcinoma - cytology (WC).

Memory device:

• AcCC - lots of "C"s: lots of cytoplasm, carcinoid-like (stippled chromatin, granular cytoplasm).

Adenoid cystic carcinoma

Features:

• Solid circular islands that are well-circumscribed.
  • Classically forms cystic structures.
• Very cellular.
• Small cells - key feature.
• Nucleus - large relative to cell (high NC ratio)
  • Often oval/triangular - may be carrot-shaped.
  • +/-Nucleolus. (???)
  • Chromatin NOT stippled.
• Scant cytoplasm - key feature.

Notes:

• Memory device: AdCC = lotsa DNA in relation to cell.

Image:

• Adenoid cystic carcinoma -cytology (WC).

Melanoma

Main article: Malignant melanoma

Features:

• Usually mixed population of:
  • Spindle cells.
    • Often single/detacted cells.
  • Epithelioid cells - usually predominant.
    • Nucleus typically eccentric.
• Brown granular cytoplasm; usually fine granularity.
• Large red nucleoli (classic finding).
• +/-Intranuclear inclusions.
• +/-Binucleation.

Minimal (for morphologic diagnosis):

1. Nuclear features of malignancy in epithelioid cells (with an eccentric nucleus) or spindle cells.
2. Brown granular cytoplasm.

Notes:

1. IHC stains are needed in many cases (S-100, HMB-45, Melan A).
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.

Lymph nodes

Normal:

• Mixed population of lymphoid cells.

Lymphoma

Non-Hodgkin's lymphoma

Features:

• Population of monomorphous lymphoid cells.
• Lymphoglandular bodies - blue-grey bodies.
  • Often about 1/2 the size of a RBC.
    • These may be seen in benign tissue.

Hodgkin's lymphoma

Features:

• Reed-Sternberg cell (diagnostic).
  • Classically binucleated.
  • Huge cell with macronucleus.
  • Each nucleus has a huge macronucleolus.
    • Macronucleolus approximately the size of a RBC.
• Commonly seen with eosinophils.

Cystic lesions of the neck

General

• One should never sign-out a cytology specimen as: "branchial cleft cyst" or "thyroglossal duct cyst".
  • The proper verbiage is "cystic squamous lesion".

DDx

Lateral:

• Brachial cleft cyst.
• Cystic hygroma.

Medial:

• Thyroglossal duct cyst.

Both:

• Epidermoid cyst.
• Cystic squmaous cell carcinoma.

Squamous carcinoma

Main article: Squamous cell carcinoma

• AKA squamous cell carcinoma.

Cytopathology

Features:

• 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):
  1. Irregular nuclear membrane, e.g. notches, sharp discontinuities.
  2. Nuclear hyperchromasia - "jet-black" nuclei on Pap stain key feature.
  3. Increased NC ratio.
  4. Variation of nuclear size from cell-to-cell.
  5. Granular chromatin.

Notes:

1. One should see abnormal squamous cells to call it SCC.
2. Poorly differentiated SCC may look like adenocarcinoma.

See also

• Cytopathology.
• Thyroid.
• Head and neck pathology.