Generalized melanosis and melanuria in a patient with metastatic melanoma

Abstract

Conflict of interest: none declared. We describe a case of generalized melanosis and melanuria in a patient with metastatic melanoma and review the pathogenesis and prognostic implications of this phenomenon. A 62‐year‐old‐man with Fitzpatrick skin type II presented with a 3‐month history of changes in a mole on his back. Histological examination of a biopsy found an incompletely excised superficial spreading melanoma (Breslow thickness 9 mm, Clark level V, nonulcerated, perineural and perivascular invasion, mitotic rate 21/mm2) with microsatellite deposits at the deep margin. A whole‐body positron emission and computed tomography (PET‐CT) scan revealed no evidence of distant metastatic disease, and baseline liver profile, full blood count and lactate dehydrogenase (LDH) level were normal. A 20‐mm wide local excision down to the fascia was performed and reported as an incompletely excised in‐transit metastasis. Fourteen months after the initial surgery, the patient presented with a 3‐month history of right‐sided chest pain, and diffuse slate‐grey hyperpigmentation of the skin (Fig. 1a) that was more pronounced in sun‐exposed areas, mucosal sites, and the nail bed. The patient’s urine became dark (Fig. 1b), with increased amounts of melanin precursors being found (dopamine creatinine ratio 1088 μmol/L; normal range 37–185). A repeat PET‐CT scan revealed disseminated disease with spleen and bone metastases but no liver involvement (Fig. 2a–d). LDH was 1964 IU/L (normal range 240–480) and renal function was preserved. Histological examination of a skin biopsy taken from an area of diffuse melanosis in the left retroauricular area found a normal epidermis, scattered perivascular papillary dermal macrophages containing melanin that stained with Fontana–Masson, and no evidence of malignancy (Fig. 2e,f).