Xeroderma pigmentosum and lentigo maligna in identical twins

Xeroderma pigmentosum (XP) is a rare autosomal recessive genodermatosis. Skin abnormalities result from an inability to repair UV-damaged DNA. Clinically, XP presents with early onset cutaneous changes (severe photosensitivity, actinic keratoses, and telangiectasias) and an increase of developing cutaneous malignancies beginning in early childhood, but lentigo maligna and melanomas are relatively rare. Here we report on homozygote twins in whom there was no positive family history. They showed subnormal physical growth. On ophthalmological examination, both had photophobia and decreased visual acuity. Since birth, several excisions had been performed for skin neoplasms. In one of them a pigmented patch developed over the frontal area which proved to be lentigo maligna and she was referred to a dermato-oncology center. They have been given isotretinoin and physical sunscreen since then. The follow-up period was extended to 2 years and no serious complications occurred from the above treatment. This is an interesting report about XP in twins with the presentation of the rare neoplasm lentigo maligna.

Contiguous lesions in lentigo maligna

BACKGROUND

Determining the best biopsy technique for a suspected lentigo maligna can be challenging. Because complete excisional biopsy is rarely practical, the physician is left to choose an appropriate area to biopsy. Sampling error can have devastating consequences, especially if the biopsy demonstrates a pigmented lesion that was considered in the clinical differential diagnosis. The presence of a solar lentigo, pigmented actinic keratosis, or reticulated seborrheic keratosis could mislead the pathologist and clinician to the erroneous conclusion that the incisional specimen is representative of the whole, and that no lentigo maligna is present.

OBJECTIVE

We have often observed the presence of a contiguous pigmented lesion adjacent to lentigo maligna. The current study was designed to determine how frequently this phenomenon occurs.

METHODS

We studied Mohs debulking specimens of lentigo maligna, and broad shave biopsy specimens of pigmented lesions on heavily sun-damaged areas of the skin proven to be lentigo maligna.

RESULTS

Contiguous pigmented lesions were present in 48% of the specimens. The most common lesion was a benign solar lentigo (30%), followed by pigmented actinic keratosis (24%).

CONCLUSION

Recognition of this phenomenon may prevent misdiagnosis of lentigo maligna related to sampling error.

[Trigeminal neuralgia presenting as a deep recurrent desmoplastic neurotropic melanoma of a lentigo maligna]

INTRODUCTION

Neurotropic melanoma is a particular anatomopathological form corresponding to dermal proliferation of desmoplastic cells of neuroid differentiation. We report a new case of neurotropic melanoma revealed by facial neuralgia.

CASE REPORT

A 64 year-old man presented in 1996 with a lentigo maligna on the right cheek treated by complete excision. After 2 years of medical supervision, a pigmented lesion recurred leading to new surgical treatment. The histological examination of the total lesion showed intra-epidermal atypical melanocyte proliferation without dermal invasion. In 1999, right trigeminal neuralgia occurred without associated cutaneous change. Cranial MRI revealed an infiltration of the right trigeminal nerve. Endo-buccal surgery disclosed a black swelling of the trigeminal nerve. Histological examination and immunohistochemistry revealed a desmoplastic melanoma.

DISCUSSION

Neurotropic melanoma with nerve invasion by malignant cells presenting as a trigeminal neuralgia is rare. Our case report underlined the depth of the neurotropic melanoma and the initial existence of a lentigo maligna without associated "neurotropic" melanoma.

[Malignant lentigo]

Lentigo maligna (LM) is a premalignant skin alteration, which may progress to lentigo maligna melanoma (LMM). LM usually appears as a small dark brown spot in the head and neck region. Over some years it may gradually enlarge to palm size and the colour become more motley. Histologically many atypical melanocytes are seen in the basal layer of the epidermis and along the adnexal structures, as well as there being dermal elastosis and a lymphohistiocytic inflammatory infiltrate in the superficial dermis. Excision should be performed as soon as the diagnosis is made to avoid more extensive excision, transplantation and development into LMM later on. If transformation of LM into LMM occurs, often after many years, fast growth, increased pigmentation and sometimes a nodular formation are observed. Histologically, the atypical melanocytes have invaded the dermis.