ARTICLE
Diagnosis: malignant metastatic melanoma presenting with generalized
melanosis and melanuria
Microscopic examination of the pigmented lesion located on the forearm
revealed a superficial spreading melanoma (Clark level IV, Breslow thickness
3.1 mm) with melanoma cells (positive for S-100 protein) within the dermis
and invading the epidermis. The histopathological examination of the eyelid
lesion showed aggregates of melanoma cells within the upper part of the
dermis but not invading the epidermis, consistent with cutaneous metastasis.
A total-body computed tomography showed multiple metastatic lesions
involving brain, mediastinal lymph nodes, liver, spleen and adrenal glands.
Support therapy and chemotherapy with Dacarbazine (800 mg/m2
i.v.) was started. However, the patient's general condition dramatically
deteriorated and he eventually died after 40 days. Autopsy confirmed the
presence of widespread metastases and revealed additional involvement
of the larynx, trachea and heart.
Comments
The patient presented with an advanced stage of widespread metastatic
melanoma, a very small primary lesion (0.5 cm in diameter) on the forearm,
and with a rare complication, melanosis and melanuria [1-6]. Melanosis
is caused by the melanin precursor 5-6 dihydroxyindole that is produced
and secreted in an increased amount by malignant cells, and then deposited
within macrophages throughout the body, where it is oxidised to melanin
[3]. Alternatively, it has been hypothesised that melanosis results from
the deposition into the skin of melanosomes (granules of melanin and its
precursors) synthesised by distant malignant melanoma cells [1]. Other
authors suggested that melanosis is secondary to unlimited spread of individual,
discrete melanoma cells to and throughout the entire skin [2]. Melanuria
is caused by the passage in urine of melanogens (melanin and other specific
metabolites) produced in large amounts by melanoma cells. Air-oxidation
of these pigments causes the characteristic coffee-like discoloration
of urine [4]. *
Article accepted on 22/11/00
REFERENCES
1. Silberger I, Kopf AW, Gumport SL. Diffuse melanosis in malignant
melanoma. Report of a case and of studies by light and electron microscopy.
Arch Dermatol 1968; 97: 671-7.
2. Konrad K, Wolff K. Pathogenesis of diffuse melanosis secondary
to malignant melanoma. Br J Dermatol 1974; 91: 635-55.
3. Fitzpatrick TB, Montgomery H, Lerner AB. Pathogenesis of generalized
dermal pigmentation secondary to malignant melanoma and melanuria. J
Invest Dermatol 1954; 22: 163-72.
4. Matons B, Bubnova E, Budesinska A, Kostirova M. Markers of
melanogenesis in malignant melanoma. Sb Lek 1994; 95: 333-8.
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