Clinical history: A 43-year-old lady presented with 3-month history of left shoulder pain. Plain film X-ray shows a well-defined lytic lesion in the left scapula. A CT-guided core biopsy of the lesion is performed and a cytology imprint is shown.
Cytologic findings
- Dispersed cell pattern
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- Mostly mononuclear but may be multinucleated
- Reniform nuclei with indents, folds and grooves ("coffee-bean")
- Abundant cytoplasm with occasional phagocytosed debris
- Distinct cell borders
- Mitoses may be present but no atypical forms Scattered histiocytic cells with abundant cytoplasm
- No significant nuclear atypia
- Associated with numerous eosinophils (red circles in the alcohol-fixed pic; hunt for them on the air-dried pic!)
- Occasional necrosis and osteoclast-type giant cells may be seen
DDx and Immunohistochemistry
Differentials to consider:
- Langerhans cell histiocytosis
- Acute and chronic osteomyelitis
- Mixed inflammatory infiltrate and histiocytes
- Langerhans cells are not typically present
- Granulomatous inflammation – no classical epithelioid histiocytes or well-formed granulomas
Confirmatory immunohistochemistry:
IHC interpretation:
- Positive stains: S100, CD1a and Langerin
- Stains to rule out differential diagnoses are usually not required
Diagnosis
Langerhans cell histiocytosis
Case writer: Dr Noel Chia
