**3. Histopathology**

In order to understand the histopathology of vitiligo, it is essential to first understand the concept of *epidermal melanin unit* [40]. Melanocytes are neural crest derivatives, and they reach their final destination of basal layer of the epidermis and hair follicles via a process of migration. Each melanocyte then transfers its melanosomes to approximately 36 keratinocytes via a unique mechanism known as the shedding vesicle system. In the normal skin in the basal layer of the epidermis for every five basal keratinocytes, there is a presence of a single melanocyte [41].

The basic histopathological finding in vitiligo is the absence of functional melanocytes in the basal layer of the epidermis (**Figure 2**) [42–44]. This absence can also be demonstrated by using special stains like Fontana-Masson (**Figure 3**) [45].

#### **Figure 2.**

*Vitiligo showing the absence of melanocytes in basal layer of the epidermis (H&E, X400).*

#### **Figure 3.**

*(a) Fontana-Masson showing the presence of melanin pigment and melanocytes in the epidermis (X400). (b) Fontana-Masson showing the absence of melanin pigment and melanocytes in the epidermis (x400).*

Immunohistochemistry for melanocyte-specific markers like HMB-45 and Melan-A and electron microscopy can also be performed for this purpose.

Other changes that have been observed include degenerative changes in the nerves and adnexa like sebaceous glands and hair follicles especially in long-standing cases [46].

In the margins of lesions especially early lesions, often inflammatory cells are seen. Principally, these cells comprise of CD4+ and CD8+ T cells [47]. These cells have been shown to demonstrate melanocyte-specific cytotoxicity [48]. At the margins of the lesions, melanocytes have been observed to show morphological changes like cellular enlargement, cytoplasmic vacuolization and long dendritic processes [29].

However, usually skin biopsy is not performed for making the diagnosis as it is primarily a clinical diagnosis. The cornerstone of its management is correct categorization of a case into its two broad types—stable and unstable vitiligo. This distinction is at present based mainly on clinical criteria because the histopathological

**25**

**Figure 4.**

*Histopathology and Molecular Pathology of Vitiligo DOI: http://dx.doi.org/10.5772/intechopen.84258*

features are not fully established. In a study carried out by the author, a reliable and systematic approach towards this diagnostic challenge has come up [49]. In that study the biopsies (3-mm punch) were taken from the margin of the active lesion. The author recommends that while evaluating biopsies from cases of vitiligo histopathological examination should be primarily focused on evaluating five histopathological variables—spongiosis, epidermal lymphocytes, basal cell vacuolation, dermal lymphocytes and melanophages (**Figure 4**). The morphological criteria used to assess these parameters are listed in **Table 1**. All the cases are then scored

*(a) Spongiosis (H&E, x400). (b) Intraepidermal lymphocytes (H&E, x400). (c) Basal cell vacuolation (H&E, x400). (d) Dermal lymphocytosis (H&E, x200). (e) Dermal melanophages (H&E, x400).*

*Histopathology and Molecular Pathology of Vitiligo DOI: http://dx.doi.org/10.5772/intechopen.84258*

*Depigmentation*

**24**

**Figure 3.**

**Figure 2.**

ing cases [46].

processes [29].

*(a) Fontana-Masson showing the presence of melanin pigment and melanocytes in the epidermis (X400). (b) Fontana-Masson showing the absence of melanin pigment and melanocytes in the epidermis (x400).*

Immunohistochemistry for melanocyte-specific markers like HMB-45 and Melan-A

Other changes that have been observed include degenerative changes in the nerves and adnexa like sebaceous glands and hair follicles especially in long-stand-

In the margins of lesions especially early lesions, often inflammatory cells are seen. Principally, these cells comprise of CD4+ and CD8+ T cells [47]. These cells have been shown to demonstrate melanocyte-specific cytotoxicity [48]. At the margins of the lesions, melanocytes have been observed to show morphological changes like cellular enlargement, cytoplasmic vacuolization and long dendritic

However, usually skin biopsy is not performed for making the diagnosis as it is primarily a clinical diagnosis. The cornerstone of its management is correct categorization of a case into its two broad types—stable and unstable vitiligo. This distinction is at present based mainly on clinical criteria because the histopathological

and electron microscopy can also be performed for this purpose.

*Vitiligo showing the absence of melanocytes in basal layer of the epidermis (H&E, X400).*

**Figure 4.**

*(a) Spongiosis (H&E, x400). (b) Intraepidermal lymphocytes (H&E, x400). (c) Basal cell vacuolation (H&E, x400). (d) Dermal lymphocytosis (H&E, x200). (e) Dermal melanophages (H&E, x400).*

features are not fully established. In a study carried out by the author, a reliable and systematic approach towards this diagnostic challenge has come up [49]. In that study the biopsies (3-mm punch) were taken from the margin of the active lesion.

The author recommends that while evaluating biopsies from cases of vitiligo histopathological examination should be primarily focused on evaluating five histopathological variables—spongiosis, epidermal lymphocytes, basal cell vacuolation, dermal lymphocytes and melanophages (**Figure 4**). The morphological criteria used to assess these parameters are listed in **Table 1**. All the cases are then scored


**Table 1.**

*Histomorphological criteria for spongiosis, epidermal lymphocytes, basal cell vacuolation and melanophages.*


#### **Table 2.**

*Vitiligo histological scoring system.*


**Table 3.**

*Final recommended diagnostic categories based on score.*

using a scoring system devised by the authors **Table 2**, and the recommended diagnoses based on these scores are shown in **Table 3**. The counting for dermal lymphocytes was done in high power (x400) of a Nikon microscope. The scoring system can be applied to both segmental and non-segmental vitiligo. Adoption of a systematic reporting system brings more consistency and objectivity in the diagnosis.

#### **4. Conclusions**

Vitiligo is a common skin disorder which is characterized by the presence of depigmented milky white macules of variable sizes. Although there are various theories on its etiopathogenesis, the consensus opinion is that vitiligo occurs due to convergence various pathways. The basic histopathological finding in vitiligo is the absence of functional melanocytes in the basal layer of the epidermis. However, in order to evaluate for stability, the histopathological examination should be primarily focused on evaluating spongiosis, epidermal lymphocytes, basal cell

**27**

**Author details**

Amit Kumar Yadav

Hospital, New Delhi, India

Department of Pathology, Vardhman Mahavir Medical College and Safdarjung

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: path.yadav@gmail.com

provided the original work is properly cited.

*Histopathology and Molecular Pathology of Vitiligo DOI: http://dx.doi.org/10.5772/intechopen.84258*

Resident, VMMC & Safdarjung Hospital.

**Notes/thanks/other declarations**

these biopsies.

**Acknowledgements**

**Conflict of interest**

None declared.

vacuolation, dermal lymphocytes and melanophages. It is recommended to score these parameters, and the final report should incorporate recommended diagnosis based on the score. This will bring more objectivity and consistency in reporting

The author wishes to acknowledge the help provided by Dr. Niti Khunger, Consultant, Dermatology, VMMC & Safdarjung Hospital, and Dr. Pallavi Mishra,

The author wishes to declare that there are no conflicts of interest.

*Histopathology and Molecular Pathology of Vitiligo DOI: http://dx.doi.org/10.5772/intechopen.84258*

vacuolation, dermal lymphocytes and melanophages. It is recommended to score these parameters, and the final report should incorporate recommended diagnosis based on the score. This will bring more objectivity and consistency in reporting these biopsies.
