Eruptive melanotic macules and papules associated with adenocarcinoma

Background: Malignancies may be associated with paraneoplastic cutaneous manifestations, including pigmentary disorders. Methods: The clinical findings were reviewed. Skin and tumor tissue samples were examined by routine histology, immunohistochemistry, and in one case also by electron microscopy. Results: Two patients developed diffuse melanotic macules and papules associated with visceral adenocarcinoma. One patient was a 64-year-old man with advanced carcinoma of the distal esophagus. The other was a 62-year-old man with metastatic pulmonary adenocarcinoma. The detection of the primary tumor in both patients was preceded by the rapid onset of melanotic macules and papules in the anogenital region and in one patient also around both nipples. The pigmented lesions were histologically characterized by a lentiginous melanocytic proliferation of large and heavily pigmented melanocytes associated with hyperpigmentation of adjacent keratinocytes. Both patients had been misdiagnosed as having epidermotropic metastatic malignant melanoma. None of them had prior, concurrent, or subsequent cutaneous or extracutaneous invasive melanoma. Both patients died of metastatic adenocarcinoma. Conclusion: Eruptive melanotic macules and papules represent an under-recognized paraneoplastic syndrome. The cases illustrate a diagnostic pitfall for clinicians and pathologists unaware of this phenomenon.