immunohistopathologically

The story

1. Proto-Indo-European*mey-
2. Proto-Indo-European*moy-nós
3. Proto-Italic*moinos
4. Latinmūnus
5. Proto-Indo-European*né
6. Proto-Indo-European*n̥-
7. Proto-Italic*n̥-
8. Latinin-
9. Latinin- -is
10. Latinimmūnis
11. Middle Frenchimmun
12. Englishimmune
13. Englishimmuno-
14. Proto-Indo-European*steh₂-
15. Ancient Greekῐ̔στός (hĭstós)
16. Englishhisto-
17. Ancient Greekπάσχω (páskhō)
18. Ancient Greekπᾰ́θος (pắthos)
19. Proto-Indo-European*leǵ-
20. Proto-Indo-European*lóǵos
21. Proto-Hellenic*lógos
22. Ancient Greekλόγος (lógos)
23. Frenchpathologie
24. Englishpathology
25. Proto-Indo-European*h₂el-
26. Proto-Indo-European*h₂élisder.?
27. Englishpathological
28. Englishhistopathological
29. Englishimmunohistopathological
30. English todayimmunohistopathologically

From immunohistopathological + -ly. By surface analysis, immuno- + histopathologically.