Dermatopathic lymphadenopathy

Dermatopathic lymphadenopathy is a rare pathology of the lymph nodes.

General

• Lymphadenopathy associated with a skin lesion - key feature.
• May be benign or malignant (e.g. T-cell lymphoma).

Microscopic

Features:

• Abundant histiocytes & special histiocytes - in loose irregular clusters - located in the sinuses, i.e. sinus histiocytosis - key feature:
  • Do not form granuloma; may be similar to toxoplasma.
• Plasma cells (medulla).
• Eosinophils.

Histiocytes & special histiocytes:

• Histiocytes:
  • +/-Melanin pigment key feature (if present).
  • Lipid-laden macrophages.
• Interdigitating dendritic cells:
  • Need IHC to identify definitively.
• Langerhans cells:
  • Classically have a kidney bean nuclei.
  • Need IHC to identify definitively.

DDx:

• Metastatic malignant melanoma - (melanin) pigmented cells have nuclear atypia, not histiocytes.
• Sinus histiocytosis - no cells with melanin.

Images

• 

  DL - very low mag. (WC)

• 

  DL - low mag. (WC)

• 

  DL - intermed. mag. (WC)

• 

  DL - high mag. (WC)

• 

  DL - very high mag. (WC)

IHC

• Interdigitating dendritic cells: S100 +ve, CD1a -ve.
• Langerhans cells: S100 +ve, CD1a +ve.

See also

• Lymph node pathology.