Melanoma in Presence of Xeroderma Pigmentosum - A Difficult Diagnosis.

A 19-year-old girl, a known case of xeroderma pigmentosum (XP) on regular follow-up, reported to us when she noticed an asymptomatic dark-colored lesion over the right forearm. Dermatological examination revealed hyperpigmented plaque measuring 2 cm × 1.5 cm over the right forearm. Surrounding skin shows mottled pigmentation with presence of hypopigmented, hyperpigmented, and depigmented macules and patches [Figure 1]. Polarized dermoscopy of lesion showed atypical pigment network, light brown, dark brown and black color; blue-white veil, white structureless area, and brown dots and globules [Figure 2a and b]. Polarized dermoscopy of surrounding skin shows diffuse white glow, reduced pigmentary network, and dark reticular pigment network with brown dots and globules. Histopathology of the lesion was consistent with superficial spreading melanoma with Clark's level II and Breslow's thickness less than 0.1 mm [Figure 3a and b].

Figure 1

Clinical image of right forearm showing hyperpigmented plaque over actinically damaged mottled skin

Figure 2

(a) Dermoscopy of surrounding skin showing diffuse white glow (blue star), normal reticular pigment network (blue arrow), thickened reticular lines (orange arrow), reduced pigmentary network (orange star), and black blotches (green arrow). (b) Dermoscopy of the lesion shows light brown, dark brown, and black color; blue white veil (red star), atypical pigment network (red arrow), crystalline structures (orange arrowhead), brown dots and globules (blue circle), and polygons (red circle) (Dermlite DL4, polarized ×10)

Figure 3

(a) Histopathology showing basal proliferation of melanocyte individually and in nests with prominent eosinophilic nucleoli extending up to papillary dermis and pigment incontinence (Breslow' s thickness <0.1 mm, Clark's level II) (H and E, 100×). (b) Melanocytes stained with melan A (Melan A, 100×)

XP is a rare autosomal recessive, DNA repair disorder, which is characterized by photosensitivity, early-onset freckles, keratitis, and high risk of melanoma and non-melanoma skin cancers. The median age of diagnosis of first cutaneous malignancy was 8 years in one study.[1] Diagnosis of these tumors is difficult due to actinic damage resulting in pigmentary alterations, lentigines, actinic keratoses, and poikilodermatous changes.[2] Usually, the melanoma is identified by ABCDE rule (asymmetry, border irregularity, color variation, large diameter, and evolving); however, applying this clinical dictum may be difficult in patients with XP. Dermoscopic features of superficial spreading melanoma are atypical pigment network, polygons, irregular blotches and dots/globules, pseudopods, regression structure, blue-white veil, negative network, crystalline structures, and atypical vascular pattern.[3] Multiple colors on dermoscopy, asymmetry, and dots and globules are seen in thin superficial spreading melanoma as was seen in our case. Dermoscopy may help in early diagnosis of melanoma in patients with XP by regular follow-up and pattern recognition.[4]

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The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

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