Negative Network Dermoscopy: Key to Melanoma Detection - IBOOLO

The negative network is represented by serpiginous, interconnecting, broadened hypopigmented lines around elongated and curvilinear globules. In a dermatoscope, a positive usually indicates that certain abnormal pathological features are detected. The benefit of the diagnosis of skin lesions is that a negative finding can help rule out melanoma, basal cell carcinoma or squamous cell carcinoma.

Fundamentals of Dermoscopy
The basic principle of dermoscopy is transillumination of a lesion in order to study it with high magnification to visualize subtle features. Light incident on a surface like the skin may be reflected, refracted, diffracted and/or absorbed. The physical properties of the skin influence these phenomena. Most light incident on dry, scaly skin is reflected, but smooth, oily skin allows light to pass through to reach the deeper dermis. Application of a linkage or immersion fluid over the skin, enhances translucency and improves visibility of subsurface skin structures of the lesion under investigation.

Dermoscopic Features of Negative Network
The “negative” of the pigmented network (also known as reverse or inverse network) consists of relatively lighter areas comprising the apparent grid of the network and relatively darker areas filling the apparent “holes”. The lighter grid lines tend to be serpiginous and the darker areas, when viewed in isolation, resemble elongated tubular or curved globules. Histopathologically, the negative network appears to correspond to thin elongated rete ridges accompanied by large melanocytic nests within a widened papillary dermis or to bridging of rete ridges. The negative network is highly specific for melanoma (95% specific), especially for a melanoma arising in a nevus.

Clinical Significance of the Negative Network
The dermoscopic descriptor “negative pigment network” (NPN) has been reported in several types of melanocytic and non-melanocytic lesions, although it has a higher frequency of association with melanoma and Spitz naevus. In a study of 401 consecutive melanomas, excluding facial, acral and mucosal locations, the frequency and variability of NPN were investigated, and the results of NPN correlated with clinical and histopathological data. NPN of any extension was found in 27% of melanomas, most frequently invasive and arising from a naevus on the trunk of young subjects. Seven percent of melanomas in the study population showed presence of NPN in more than half of the lesion area; most of these did not show typical dermoscopic melanoma features.

Steps in Performing Dermoscopy
When skin magnification is performed, the magnification of the dermatoscope is adjusted according to the size of the examined area and the details required. Observe the window of the dermatoscope until the area under observation is clear. As well as to avoid too close contact between the dermatoscope and the skin, so as not to affect the observation effect or produce errors.
Although the non-invasive examination of dermoscopy can provide a lot of information, the final diagnosis may still need to be confirmed by skin biopsy and pathology. For suspicious lesions found during dermoscopy, doctors may consider further pathological section examination.

How to Analyse Dermatological Images to Identify Negative Network
The Negative network is defined by serpiginous lighter grid lines that are linked with hyperpigmented, elongated to curvilinear globules. The negative network from a histological point of view seems to match with the thin elongated and hypopigmented rete ridges that are bridging and encircling large melanocytic nests in a widened dermal papillae. There are Dermoscopy tumour simulacra and mimics. False positive diagnosis may lead to unnecessary excisions. Missing a cancer case is much more risky as it may lead to severe consequences for the patient and the doctor as well as false negative diagnosis.

Negative Results and Other Diagnostic Methods
Dermoscopy is widely used for the evaluation of melanotic lesions and also as an aid in the diagnosis of vascular diseases and parasitic skin infections. It has the advantage of being non-invasive and rapid, but has limited diagnostic value for non-pigmented lesions. The technique of Histopathological examination secures tissue samples by skin biopsy for pathological examination. Even though it is an invasive technique it is the gold standard for the diagnosis of many difficult skin diseases like skin cancer, lupus erythematosus, pemphigus; however, it is an invasive process and can be prone to sampling bias. Only in the case of a high clinical suspicion of a disease dermoscopy can be negative and further skin biopsy, PCR or immunological testing can be done. If direct microscopy is negative in a dermatomycosis case but there is high suspicion of the disease, fungal culture may be done.

Negative Networks in Skin Health Monitoring
A baseline of an individual’s health is established through skin health surveillance. The result that does not show a suspicious melanotic lesion is negative and can be used as a reference for future surveillance. A number of patients are concerned with the outcome of skin tests, and doctors should tell them that a negative result indicates that there is no evidence of disease at this time, not no disease at all time. It is best to have the patients do check up regularly dermoscopy and have the patients save dermoscopic images as recommended by their doctors. It can then be compared with the digital images of different periods of time in order to detect the lesions.

Challenges and Misconceptions of Negative Results
Some analyses are not a magic wand; each one is different and has its own sensitivity and specificity. It is also important to understand that it is impossible to exclude all diseases with 100% confidence from a result. For example, not all melanomas are detectable in the early or subclinical stages, so dermoscopy may not detect the lesion. Dermoscopy can be used in conjunction with histological biopsy, or PCR with fungal culture, which can increase the diagnostic yield and prevent wrong diagnosis with negative findings.

Conclusion
Dermoscopy results negative may provide a less anxious patient with skin cancer or other serious skin diseases. High risk group or family history of skin diseases patients should also maintain routine check up schedule with the doctor even if the patient has no lesions. There is no zero risk for the condition from a negative result, and this is particularly so for those with high prevalence risk factors for skin diseases. Hence, patients should still practice good skin health through education, lifestyle changes.