Granular cell tumour

The granular cell tumour is a rare histomorphologically distinctive neoplasm found at many sites. The classic location is the head and neck.

Granular cell tumour
Diagnosis in short
Granular cell tumour. H&E stain.
LM	cells with abundant eosinophilic granular cytoplasm (granules ~ 1-3 micrometers, poorly demarcated on LM), +/-pseudoepitheliomatous hyperplasia
Subtypes	benign (common), malignant (uncommon)
LM DDx	squamous cell carcinoma, oncocytoma, adjacent ulcer, xanthoma, melanocytic nevus with neurotization
Stains	PAS +ve
IHC	S-100 +ve, CD68 +ve (cytoplasmic), vimentin +ve (membranous), calretinin +ve (usually)
EM	abundant lysosomes
Gross	yellow nodule
Site	typically head and neck - other sites: breast, skin, tongue, esophagus + more
Syndromes	LEOPARD syndrome
Prevalence	rare
Prognosis	usually good (benign)
Clin. DDx	xanthoma, other skin lesions

General

• Rare.
• Usually benign.
• May seen in the context of LEOPARD syndrome and a mutation in the PTPN11 gene.
  • PTPN11 = protein-tyrosine phosphatase non-receptor type 11.
    • Gene implicated in Noonan syndrome 1.
• May mimic (well-differentiated) squamous cell carcinoma - histopathologically.
  • There is a well-described phenomenon called pseudoepitheliomatous hyperplasia.

Aside:

• Pseudoepitheliomatous hyperplasia is seen in:
  1. Fungal infections.
  2. Inflammatory papillary hyperplasia.
  3. Granular cell tumour.
  4. Adjacent to an ulcer.

Sites

May be seen in any number of sites:

• Granular cell tumour of the breast.
• Granular cell tumour of the skin.
• Granular cell tumour of the tongue.
• Granular cell tumour of the esophagus.

Gross

• Yellow nodule.

DDx of yellow nodule:

• Granular cell tumour.
• Lipoma.
• Xanthoma.

Microscopic

Features:

• Cells with abundant eosinophilic granular cytoplasm - key feature.
  • Granules (represent abundant lysosomes):
    • Size: 1-3 micrometers.
    • Poorly demarcated (on light microscopy).
• Nested architecture.
• +/-Pseudoepitheliomatous hyperplasia.
  • May mimic SCC.

DDx:

• Squamous cell carcinoma.
• Oncocytoma.
• Melanocytic nevus with neurotization.
• Xanthoma.

Malignant features

Features of malignancy (3 of 6 required):

• Necrosis.
• Spindled tumour cells.
• Vesciular nuclei with large nucleoli.
• Mitoses (>2/10 HPF at 200x).
• High NC ratio.
• Pleomorphism.

Predictive of poor outcome:

• Ki-67 >10%.

Special stains

• PAS +ve.

IHC

Features:

• S100 +ve.
• CD68 +ve (cytoplasmic).
• Vimentin +ve (membranous).
• Calretinin +ve (90-95%).

Images

• 

  GCT. (WC)

• 

  GCT - S-100. (WC)

EM

• Abundant lysosomes.
  • Round structures with variable (electron) density.

Images:

• Granular cell tumour - several LM and EM images (ucsf.edu).

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SKIN LESION, NECK, EXCISION:
- GRANULAR CELL TUMOUR.
- MILD SOLAR ELASTOSIS.

COMMENT:
The lesional cells stain as follows:
POSITIVE: S-100, CD68, vimentin, calretinin.
NEGATIVE: HMB-45.

Micro

The sections show skin with nests of cells in the mid dermis, extending to the subcutis. The cells that make up the nests have an abundant granular grey cytoplasm, and round regular nuclei without obvious nucleoli. No mitotic activity is readily apparent. The lesional cells focally wrap around nerve. The superficial dermis has mild solar elastosis. The lesion is completely excised in the plane of section.

See also

• Esophagus.
• Head and neck pathology.