Vitiligo-like hypopigmentation and metastatic melanoma of unknown primary site: friends or foes?

Abstract

To the Editor, Malignant Melanoma (MM) is a tumour with significant impact on society. Although in the vast majority of MM patients the primary site of the tumour at the time of diagnosis is well known, many patients may develop a melanoma of unknown primary site (MUP) that seems to carry a better prognosis than those with known primary site [1]. Interestingly, about 3% of MM patients of known primary site may develop vitiligo or vitiligo-like areas, whose appearance seems to represent a positive prognostic factor [2]. Conversely, what is the incidence of vitiligo or vitiligo-like lesions in MUP patients and their related prognosis seems to be unclear. To the best of our knowledge, we report for the first time a case of cutaneous metastasis, surrounded by areas of vitiligo-like hypopigmentation, in a MUP patient, whose prognosis was suddenly and inevitably fatal, despite the presence of two alleged favourable prognostic factors. A 68-year-old man presented with a 6-months history of multiple bulges localized at the left thigh; some of the them had superficial erosions and some others necrotizing areas (Fig. 1), surrounded by areas of vitiligo-like hypopigmentation (Fig. 1, black arrows). On physical examination, he appeared weak and debilitated. He denied having a past history of a primary melanoma excision or family history of MM and/or vitiligo. Histology from bulging lesions showed nest of giant atypical, anaplastic and multinucleated melanocytes, with eosinophilic cytoplasm and few lymphocytes (Fig. 2a), and immunohistochemistry showed neoplastic cells with intracytoplasmatic positivity to Melan A (Fig. 2b) consistent with metastases of MM. Unfortunately, patient refused to receive another cutaneous biopsy on vitiligo-like lesions. Since no history of previous melanoma was reported and accurate and thorough oropharyngeal, otorhinolaryngological, ophthalmological, anogenital, cutaneous examinations failed to identify any primary lesion, a diagnosis of MUP was made. A total body nuclear magnetic resonance and position electron tomography/computed tomography scan revealed the presence of diffuse visceral metastases and, thus, in agreement with the AJCC Staging Task Force [3], a diagnosis of stage IV disease was made. Patient died 3 months after receiving the certain diagnosis of metastatic MUP. The aetiology of MUP still remains unknown; one hypothesis suggests that MUP may arise from some melanocytes located in lymph nodes, viscera or other subcutaneous tissues, which undergo malignant transformation [4]. The most likely explanation seems to reside into a complete spontaneous regression of the primary melanoma, leaving areas of vitiligo, which might hide the primary [1], and, thus, represent an additional clue to promptly detect it. J. C. Salas-Alanis (&) Department of Dermatology, Facultad de Medicina y Hospital Universitario Dr. Jose E. Gonzalez, Universidad Autonoma de Nuevo Leon, Avenida Gonzalitos No. 235 Norte, Colonia Mitras Centro, CP64460 Monterrey, Nuevo Leon, Mexico e-mail: drjuliosalas@gmail.com