Granuloma annulare

Granuloma annulare is relatively uncommon problem in dermatopathology.

Granuloma annulare
Diagnosis in short
Granuloma annulare. H&E stain.
LM	Palisading granulomas around necrobiotic collagen and mucin
Subtypes	superficial (common), deep (not common)
LM DDx	rheumatoid nodule, necrobiosis lipoidica, epithelioid sarcoma
Stains	alcian blue stain (pH 2.5)
Gross	usu. arms and hands, papules
Site	skin
Prognosis	benign

General

• Benign and self-limited condition.
• Etiology unknown - may be assoc. with trauma.

Gross

• Typically extremities - usu. arms and hands.

Image

• 

  Granuloma annulare. (WC)

Microscopic

Features:

• Dermal palisading granuloma - typically superficial-to-mid dermis - surrounds:
  • Necrotic collagen - key feature.
    • Nuclei "missing" - have undergone karyolysis.
  • Mucin - important.
    • Loose/pale, paucicellular, eosinophilic.
• Chronic inflammatory cells.

Notes:

1. There may be multiple small foci with intervening normal dermis.
2. Granuloma annulare can be subclassified into subcutaneous and interstitial.
3. Histomorphologically similar to Rheumatoid nodule.
4. Neutrophils may be seen.

DDx:

• Necrobiosis lipoidica - little mucin, no normal dermis between foci, plasma cells - common, may involve the fat - tend to be deeper.
• Rheumatoid nodule - has fibrin in the core of the granuloma (instead of mucin), multinucleated macrophages more common.
• Epithelioid sarcoma - esp. if the lesion appears to be mid-to-deep dermis.

Images

• 

  Granuloma annulare - intermed. mag. (WC/Nephron)

• 

  Granuloma annulare - high mag. (WC/Nephron)

• 

  Granuloma annular - palisaded granuloma - high mag. (WC/Nephron)

www:

• Granuloma annulare (dermaamin.com).

Stains

• Alcian blue (pH 2.5) +ve (for mucin).

Image:

• Granuloma annulare (nih.gov).

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SKIN LESION, UPPER BACK, PUNCH BIOPSY:
- SUPERFICIAL PALISADING GRANULOMAS WITH CORES OF NECROBIOTIC COLLAGEN, AND SCANT
  MUCIN; CONSISTENT WITH GRANULOMA ANNULARE.

Skin lesion, left elbow, excision:
- Palisading granulomas with cores of necrobiotic collagen, and scant mucin
  consistent with granuloma annulare.

COMMENT:
An alcian-blue stain (pH 2.5) shows scant mucin.  The granulomas are relatively deep;
however, plasma cells are not apparent. The differential diagnosis is rheumatoid nodule.

Micro

The sections show superficial palisading granuloma with cores of necrobiotic collagen and scant mucin. No plasma cells are apparent.

The overlying epidermis is unremarkable.

See also

• Dermatopathology.
• Non-malignant skin disease.