Lymph node metastasis

Lymph node metastasis is cancer that has spread to a lymph node.

Lymph node metastasis
Diagnosis in short
Lymph node metastasis (colorectal carcinoma). H&E stain.
LM	malignant cells foreign to the lymph node - dependent on specific cancer
Subtypes	micrometastasis, macrometastasis
LM DDx	endometriosis, ectopic decidua, endosalpingiosis, melanocytic nevus, dermatopathic lymphadenopathy, sinus histiocytosis, tumour deposit (dependent on site), isolated tumour cells, pathology of the lymph node - see lymph node pathology and lymphoma
Stains	dependent on tumour
IHC	dependent on tumour
Gross	enlarged lymph node, esp. spherical, white mass
Site	lymph node - see lymph node pathology
Clinical history	+/-suspicion of cancer
Signs	+/-nodule at site of a lymph node
Prognosis	dependent on specific type of cancer, +/-number of nodes affected
Clin. DDx	reactive lymphadenopathy, lymphoma, other benign causes of lymphadenopathy - see lymph node pathology
Treatment	dependent on underlying cancer

General

• Determination of lymph node status is one of the most common indications for the examination of lymph nodes.
• It is a good idea to look at the tumour (if available) ...before looking at the LNs for mets.
• Lymph node metastasis, in the absence of other metastases, often up-stage a cancer from stage II to stage III.

Gross

• Outside:
  • "Large" - size varies by site.
    • Neck >10 mm.
  • Shape - round more suspicious than oval.
• Sectioned:
  • White firm lesion with irregular border - classic appearance.
  • Non-fatty hilum.

Microscopic

Features:

• Foreign cell population - key feature.
  • Classic location: subcapsular sinuses.
• +/-Cells with cytologic features of malignancy.
  • Nuclear pleomorphism (variation in size, shape and staining).
  • Nuclear atypia:
    • Nuclear enlargement.
    • Irregular nuclear membrane.
    • Irregular chromatin pattern, esp. asymmetry.
    • Large or irregular nucleolus.
  • Abundant mitotic figures.
• +/-Cells in architectural arrangements seen in malignancy; highly variable - dependent on tumour type and differentiation.
  • +/-Gland formation.
  • +/-Single cells.
  • +/-Small clusters of cells.

Notes:

1. Cytologic features of malignancy may not be present; some tumours, e.g. gallbladder carcinoma, do not always have overt cytologic features of malignancy.
   • The diagnosis is based on the fact that they are foreign to the lymph node and architecturally consistent with a well-differentiated malignancy.
2. Lymph node metastases in sarcomas are uncommon; they are seen in <3% of cases.
3. Fatty lymph nodes (esp. fatty hilus) are less likely to harbor metastases.

DDx - mimics of metastatic disease:

• Endometriosis.
• Ectopic decidua.
• Endosalpingiosis.
• Melanocytic nevus - intracapsular or within the trabeculae.
• Dermatopathic lymphadenopathy.^{[citation needed]}
• Sinus histiocytosis - especially for the junior resident.
• Tumour deposit (discoutinuous extramural extension) - definition dependent on primary tumour (e.g. in the head & neck they are tumour replaced lymph nodes, in the colon they are considered separate and not counted as lymph nodes).

Images

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  Breast carcinoma LN metastasis (WC)

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  Thyroid carcinoma LN metastasis (WC)

• 

  Colorectal carcinoma LN metastasis (WC)

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  Melanoma in a lymph node. (WC)

Mimics

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  Decidua in a LN - low mag. (WC)

• 

  Decidua in a LN - high mag. (WC)

• 

  Endometriosis in a LN - intermed. mag. (WC)

• 

  Endosalpingiosis in a LN - intermed. mag. (WC)

• 

  Endosalpingiosis in a LN - very high mag. (WC)

See also

• Lymph node pathology.
• Cancer.
• Cancer staging.