Clinical Synopsis
A 32year old female presented with a four year history of depigmented patches on the face
trunk and extremities. These depigmented patches were irregular, well demarcated and nonpruritic. Both lips were affected sparing the hands and the feet. Six months prior to presenting
to our clinic, a small nodule appeared in a depigmented patch on the left leg. The nodule
rapidly increased in size and became ulcerated. At the time of presentation the tumor
measured 4cm in diameter (Fig. 1). Thorough examination of the left limb did not reveal any
other growths. The inguinal lymph nodes were not enlarged. She had no personal or family
history of melanoma.
Fig. 1: Lateral (A) and aerial (B) view of a tumor arising from the centre of a vitiligo patch.
The Brown coloration is due to povidone iodine
An excision was done with a 1cm safety margin and deeper to subcutaneous tissue. The
histological examination the tumor was composed of nested atypical melanocyte (Fig. 2). The
tumor cells expressed S-100, Melan-A (Fig. 3) and HMB-45. The proliferation activity was
high (MIB-1) with many mitotic figures. At six months follow up there was complete healing
without recurrence and no changes in the inguinal nodes. The patient was later lost to follow
up.
Fig. 2: H & E showing nested atypical melanocytes
Fig. 3: Tumor cells stained positive with Melan-A
Discussion
The prevalence of vitiligo in the general population is estimated at 1%1 while the prevalence
of vitiligo in patients with malignant melanoma has been reported to range from 3%-6%2,3.
There are different depigmentary changes associated with melanoma; ranging from halo
nevus, achromic patches on melanoma scars, depigmentation of injection site of
immunotherapy and depigmentation associated with regressing malignant melanoma. The
association of vitiligo with regressing melanoma has been widely reported in literature,
however primary melanoma presenting initially with vitiligo is very rare. Lugo-Somolinus et
al4 reported two cases of vitiligo-like primary melanoma. We report a case of primary
melanoma arising in vitiliginous lesion.
The pathologic mechanism of vitiligo is not clearly known. Complex factors involving
cellular and humoral immunity, toxic metabolites and genetic factors partly contribute to its
pathogenesis. Ciuet al5 demonstrated that antibodies to melanocytes were present in both
vitiligo and melanoma patients which were directed to similar melanocyte antigens. The
implicated antigens are tyrosinase, melan A, gp100 and TRP-26. This association explains the
simultaneous appearance of vitiligo and regressing melanoma but contradicts the occurrence
of melanoma in vitiligo lesions.
Tobin et al7 observed that melanocytes are never completely cleared from vitiligo lesions and
that this melanocyte can recover their functionality. Similary, Gottschalk et al8 reported
melanocyte survival in three cases of vitiligo which had been inactive for 2-5years. Melanoma
may develop from these melanocytes that have escaped immune destruction. The mechanisms
of immune escape are not clearly known but Le Poole et al9 hypothesized that the tumor
escape may be due to early activation of T-cells secreting IFN-α which contribute to tumor
escape and development of vitiligo.
Vitiligo-like lesions are generally regarded as a good prognostic factor in melanoma
patients10,11. The survival rate of these patients has been shown to be better than would have
been expected for a patient with a similar melanoma stage. This may be attributed to
destruction of melanocyte by an enhanced immune response
In conclusion, we present a patient with a rapidly growing amelanotic melanoma arising from
vitiligo lesions without evidence of tumor elsewhere. The six months follow up period might
be short to assess the recurrence.
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