Nucleolus

Micrograph showing a tumour (epithelioid sarcoma) with prominent nucleoli. H&E stain.

The nucleolus (plural nucleoli) is a thingy in the nucleus that may give the pathologist a clue to what they are looking at.

Generally speaking, large nucleoli suggest something is happening - they are associated with gene transcription. Large nucleoli are seen in malignancies and reactive conditions.

Macronucleolus

Almost the size of RBC ~ 6-7 micrometers.

Example:

• Reed-Sternberg cell (Hodgkin lymphoma) ~ 5-7 micrometers.

Image:

• Extreme nuclear enlargement with huge macronucleoli (WC).

Red nucleolus

Large - can be seen with 10x objective.

Examples:

• Melanoma.
• Serous carcinoma.

Large nucleolus

Large - can be seen with 10x objective.

Examples:

• Melanoma.
• Carcinoma.
  • Serous carcinoma.
• Adenocarcinoma.
  • High-grade renal cell carcinoma.
• Sarcoma:
  • Epithelioid sarcoma.
  • Malignant rhabdoid tumour.
  • Atypical teratoid/rhabdoid tumour.
  • Epithelioid angiosarcoma.

• Ganglion cell:
  • Ganglion (benign).
  • Gangliocytic paraganglioma.
  • Ganglioneuroma.

Medium-sized nucleolus

Medium - can be seen well with 20x objective.

Examples:

• Prostatic adenocarcinoma.
• Oncocytoma.
• Mammary carcinoma, no special type.
• Embryonal carcinoma.
• Squamous metaplasia of the uterine cervix.

Small

Small - hard to see at 20x objective, seen with 40x objective.

Examples:

• Squamous cell carcinoma.
• Mucoepidermoid carcinoma.

Indistinct nucleolus

Not present - cannot see with 40x objective.

Examples:

• Small cell carcinoma.
• Neuroendocrine carcinoma.

See also

• Basics.