[525] Interobserver Agreement of Assessment of Desmoplasia and Neurotropism in Melanoma
Rajmohan Murali, Elyn R Riedel, Klaus J Busam, Wendy A Cooper, Maria Garrido-Ruiz, Rooshdiya Z Karim, Tamazin Leecy, Melissa P Pulitzer, Richard A Scolyer. Memorial Sloan-Kettering Cancer Center, New York; Royal Prince Alfred Hospital, Sydney, Australia; Melanoma Institute Australia, Sydney, Australia
Background: A proposed scheme for classification of desmoplastic melanoma (DM) divides melanomas that exhibit desmoplasia into pure DM [pDM, in which ≥90% of invasive tumor is desmoplastic] and combined DM [cDM, in which <90% of invasive tumor is desmoplastic]. This classification of DM type correlated with survival in some studies but not in others. One possible reason for these conflicting findings is that the assessment and classification of desmoplasia is not reproducible. We sought to determine the level of interobserver agreement in the classification of desmoplasia and neurotropism in melanoma.
Design: Hematoxylin-eosin-stained slides from 50 cases of melanoma exhibiting varying degrees of desmoplasia and neurotropism were scored by 6 pathologists. Each observer scored the following: DM type (pDM or cDM); nerve involvement (absent, focal or extensive); location of nerve involvement (within or outside main tumor mass, or both); and whether the tumor should be termed “neurotropic melanoma”. The level of interobserver agreement for each parameter was assessed using kappa (k) statistic.
Results: Agreement for assessment of DM type, nerve involvement, location of nerve involvement, and whether the observer would classify the tumor as “neurotropic melanoma” were moderate (k=0.47), fair (k=0.31), slight (k=0.13) and fair (0.39), respectively (Table).
| Observer-> | 1* | 2* | 3* | 4* | 5* | 6* | Kappa |
|---|---|---|---|---|---|---|---|
| DM type | 0.47 | ||||||
| Pure DM | 22(44) | 37(74) | 30(60) | 33(66) | 32(64) | 23(46) | |
| Combined DM | 18(36) | 13(26) | 12(24) | 13(26) | 15(30) | 19(38) | |
| Not DM | 10(20) | 0 | 8(16) | 4(8) | 3(6) | 8(16) | |
| Nerve involvement | 0.31 | ||||||
| Absent | 17(34) | 26(52) | 30(60) | 24(48) | 10(20) | 29(58) | |
| Focal | 9(18) | 23(46) | 3(6) | 5(10) | 6(12) | 2(4) | |
| Extensive | 24(48) | 1(2) | 17(34) | 21(42) | 34(68) | 19(38) | |
| Location of nerve involvement | 0.13 | ||||||
| Within main tumor mass | 11(33) | 3(13) | 12(60) | 6(23) | 15(37) | 5(24) | |
| External to main tumor mass | 3(9) | 18(75) | 1(5) | 8(31) | 7(18) | 2(10) | |
| Both within and external | 19(58) | 3(13) | 7(35) | 12(46) | 18(45) | 14(67) | |
| Neurotropic melanoma | 0.39 | ||||||
| No | 30(60) | 27(54) | 32(64) | 24(48) | 10(20) | 29(58) | |
| Yes | 20(40) | 23(46) | 18(36) | 26(52) | 40(80) | 21(42) |