The influence of clinical information in the histopathologic diagnosis of melanocytic skin neoplasms

Abstract

Background: We tested the relevance of clinical information in the histopathologic evaluation of melanocytic skin neoplasm (MSN).

Methods: Histopathologic specimens from 99 clinically atypical MSN were circulated among ten histopathologists; each case had clinical information available in a database with a five-step procedure (no information; age/sex/location; clinical diagnosis; clinical image; dermoscopic image); each step had a histopathologic diagnosis (D1 through D5); each diagnostic step had a level of diagnostic confidence (LDC) ranging from 1 (no diagnostic certainty) to 5 (absolute diagnostic certainty). The comparison of the LDC was employed with an analysis of variance (ANOVA) for repeated measures.

Findings: In D1 (no information), 36/99 cases (36.3%) had unanimous diagnosis; in D5 (full information available), 51/99 cases (51.5%) had unanimous diagnosis (p for difference between proportions <0.001). The observer agreement expressed as kappa increased significantly from D1 to D5. The mean LDC linearly increased for each observer from D1 through D5 (p for linear trend <0.001). On average, each histopathologist changed his initial diagnosis in 7 cases (range: 2-23). Most diagnostic changes were in D2 (age/sex/location).

Interpretation: The histopathologic criteria for the diagnosis of MSN can work as such, but the final histopathologic diagnosis is a clinically-aided interpretation. Clinical data sometimes reverse the initial histopathologic evaluation.

Figure 1. A 69-year-old man with a lesion from the back showing clinical (top left) and dermoscopic (top right) features of regression .

Histopathologically, the lesion is medium to large in size and shows a regular epidermal hyperplasia (bottom left). The main feature of atypia is the presence of areas of prevailing single cell proliferation at the junction (bottom right). Lentiginous melanocytic proliferations of the elderly are often controversial from both a both conceptual and a practical point of view. The lesion at issue was diagnosed as melanoma in situ, lentiginous type, by six histopathologists in D1 and by eight histopathologists in D5.

Figure 2. A 20-year-old woman with a lesion from the leg showing clinical (top left) and dermoscopic (top right) features consistent with pigmented Spitz naevus .

Histopathology revealed a sharply circumscribed, medium-sized lesion which was mainly characterized by nests of melanocytes at the junction (bottom left; haematoxylin-eosin, ×40). However, in some worrisome microscopic fields, melanocytes at all levels of the epidermis were seen (bottom right; haematoxylin-eosin, ×250). Due to these conflicting features, in the absence of any clinical information the lesion was diagnosed as melanoma by three histopathologists and as naevus by seven histopathologists. With the knowledge of the complete clinical information, the lesion was finally diagnosed as benign by all the histopathologists.

Figure 3. The increase of the mean LDC for each histopathologist according to the diagnostic steps.

On the horizontal axis: 1 – No clinical information. 2 – Age and sex of the patient; location of the lesion. 3 – Clinical diagnosis. 4 – Clinical image. 5 – Dermoscopic image.

Figure 4. A hypopigmented lesion (top left) from the back in an 18-year-old woman dermoscopically showing atypical vessels and reticular depigmentation (top right).

Histopathology reveals a large-sized and asymmetric lesion with focal flattening of the dermoepidermal junction (bottom left); in some areas there is some irregular spacing of junctional nests and some pagetoid spreading (bottom right). The lesion was finally diagnosed as congenital nevus by all the histopathologists; two of these panelists changed in D2 their first diagnosis of ‘unknown’.