1. Lananh Nguyen, M.D. Division of Neuropathology University of Pittsburgh Medical Center 15-year-old boy presenting with back pain and skull lesion

2. Patient complained of back pain. An MRI was done (not shown) which showed multiple osseous lesions in the spine and pelvis. A biopsy of the pelvis was called chronic osteomyelitis. On physical exam, a nontender growing skull lesion was seen. And, imaging was performed. Clinical history 2

3. 3 Radiology: Identify the lesion and name the 3 imaging modalities used below.

4. 4 T1 T2 T1 with contrast Radiology: Imaging of the skull lesion. Identify the lesion and name the 3 imaging modalities used below.

5. Click on the hyperlink below to view the virtual slide –Intraoperative smearIntraoperative smear What do you see on the smear? 5 A biopsy was performed and an intraoperative consultation was requested.

6. 6 A biopsy was performed and an intraoperative consultation was requested. What do you see on the smear? Low power

7. 7 Giant cells Numerous macrophages A biopsy was performed and an intraoperative consultation was requested. What do you see on the smear? Low power

8. This is the same smear at higher power. What do you see? 8 High power

9. 9 Nuclear indentation Nuclear groove This is the same smear at higher power. What do you see?

10. 10 This is what the H&E permanent slides look like. Click on the hyperlink below to view the virtual slide –Permanent H&E slidePermanent H&E slide What do you see on the slide?

11. This is what the H&E permanent slides look like. 11

12. What is your diagnosis? 12

13. We’re not telling the diagnosis yet. What immunohistochemical stains would you like to do? 13

14. These were ordered –S100 –CD68 PGM –CD1a –Langerin –CD163 What is in the differential based on this panel? What immunohistochemical stains would you like to do? 14

15. ImmunostainLangerhan Cell Histiocytosis Juvenile Xanthogranuloma Reactive histiocytes S100 CD68 PGM CD1a Langerin CD163 Fill in the panel by denoting “+” or “–” 15

16. ImmunostainLangerhan Cell Histiocytosis Juvenile Xanthogranuloma Reactive histiocytes S100+-+/- CD68 PGM-++ CD1a+-- Langerin+-- CD163-++ Fill in the panel by denoting “+” or “-”. 16

17. Immunohistochemical stains 17 CD1aLangerin

18. CD1a: majority of cells, including cells with nuclear grooves and nuclear indentations (LC-Langerhans cell) show strong membranous staining Langerin: there is strong staining in cells which are also CD1a+ What do you see on the stains? 18

19. Immunohistochemical stains 19 S100CD68 PGMCD163

20. What do you see on the stains? 20

21. CD1a: majority of cells, including cells with nuclear grooves and nuclear indentations (LC-Langerhans cell) show strong membranous staining Langerin: there is strong staining in cells which are also CD1a+ S100: positive blush in cells CD68: majority of cells, including LC, are negative in with a background of positive cells CD163: majority of cells, including LC, are negative in with a background of positive cells What do you see on the stains? 21

22. What is your final diagnosis? 22

23. Final diagnosis: Langerhans cell histiocytosis –Given the clinical presentation –Given the histologic morphology of nuclear grooves and nuclear indentations specific to Langerhan cells –Given the CD1a and Langerin positive immunophenotype for Langerhan cells What is your final diagnosis? 23

24. Discussion: Histocytic developmental pathway 24 Adapted from Weitzman and Jaffe, 2005

25. Histiocytic lesion in skull CD1a+/Langerin+ Langerhans cell histiocytosis HX: skin rash or painful bone lesion. Systemic sx of fever, weight loss, diarrhea, edema, dyspnea, polydipsia, and polyuria H&E: nuclear groove, nuclear indentation CD1a+ : many cells, if clustered then suspicious Langerin+: staining in same cells. Normal BM: rare to none Malignancies with histiocytic morphology Lymphoma Leukemia Sarcoma CD1a-/Langerin- Juvenile xanthogranuloma family Juvenile xanthogranuloma Erdheim-Chester Rosai DorfmannMacrophages Reactive macrophages Hemophagocytic disorders 25 Algorithm for histocytic lesion in bone for neuropathologists