title: Malignant melanoma arising in melanin-producing medullary thyroid carcinoma.
abstract: BACKGROUND
  We report a case of malignant melanoma arising in medullary thyroid carcinoma that has not yet been described.
  
  
  METHODS
  A 66-year-old woman presented with a mass in her thyroid. The resected mass was black in color, and was composed of a mixture of classic medullary thyroid carcinoma and pleomorphic atypical cells containing melanin pigments. The pleomorphic atypical cells were morphologically consistent with malignant melanoma, and expressed Melan-A, HMB-45, and S-100 protein as determined by immunohistochemistry. Some of these cells were also positive for calcitonin and chromogranin A. Although the malignant melanoma metastasized to the lymph nodes, the patient remained free from local recurrence and distant metastasis and the primary malignant melanoma lesion was not identified for up to 11 years after the thyroidectomy.
  
  
  CONCLUSIONS
  11 melanin-producing MTC cases have been reported to date. In the reported cases, the term "malignant melanoma" was not used, likely because the melanin-containing carcinoma cells were not morphologically consistent with malignant melanoma, but with medullary carcinoma.
  
  
  CONCLUSIONS
  Malignant melanoma arising in MTC may have a favorable prognosis.
authors: Department of Diagnostic Pathology, Kuma Hospital, Kobe, Hyogo, Japan. Electronic address: mhirokawa@kuma-h.or.jp.
authors: Mitsuyoshi
authors: M
authors: Hirokawa
authors: Department of Surgery, Kuma Hospital, Kobe, Hyogo, Japan.
authors: Akira
authors: A
authors: Miyauchi
authors: Department of Surgery, Kobe Ekisaikai Hospital, Kobe, Hyogo, Japan.
authors: Minoru
authors: M
authors: Otsuru
authors: Department of Diagnostic Pathology, Faculty of Medicine, Oita University, Yufu, Oita, Japan.
authors: Tsutomu
authors: T
authors: Daa
keywords: Malignant melanoma; Medullary carcinoma; Melanin pigment; Thyroid