Investigators presented a rare case study describing the coexistence of medullary thyroid carcinoma (MTC) and malignant skin melanoma within a single patient’s thyroid following a total thyroidectomy, according to Clinical Case Reports. The tumors were separated within the thyroid with no shared anatomy.

Upon microscopic evaluation, one tumor was a multinodular goiter, while the other contained prominently black-pigmented, epithelioid cells. The patient was a 68-year-old Lebanese woman who had reactive and/or metastatic lymph nodes and a benign chest hemangioma. Investigative imaging and examination of the patient’s skin negated the presence of any possible primary site of the metastasized melanoma.

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Following reverse transcription-polymerase chain reaction analysis, the patient was negative for any BRAF gene mutations, which is a common occurrence in aggressive cases of melanoma, according to the authors. This caused a diagnostic dilemma in attempting to determine the origin of the melanoma as no primary site of origin was identifiable.

Immunohistochemistry profiling revealed that the multinodular goiter was consistent with MTC with positivity for synaptophysin, TTF-1, and calcitonin with a low signal (5%) for Ki-67 proliferation. The suspected malignant melanoma nodule showed around 15% focal staining for Ki-67 proliferation along with S100, Melan A, and HMB-45.

Repeated epigenetic DNA methylation analyses classified the latter tumor as a skin cutaneous melanoma without a primary site of origin. The investigators could not classify the multinodular tumor using DNA methylation profiling because the EPICUP database did not include rare MTC tumor types among the 38 tumors listed.

This study was the first to utilize epigenetic DNA methylation profiling along with microscopy to determine the origin of the 2 neoplasms, the authors said. “To the best of our knowledge, similar to our work only two prior studies have reported the coexistence of melanoma with MTC with no other primary,” they wrote. However, neither of these studies performed detailed molecular investigation.

The authors strongly emphasized the clinical importance of performing a detailed molecular analysis using immunohistochemistry, genetic testing, and DNA methylation profiling to thoroughly investigate the tumor type and site of origin. Therefore, doctors confronted with rare cases such as this could more accurately prescribe the best tumor-type specific therapy which would improve the patient’s chance of survival. In this case, the patient received treatment with nivolumab and successfully maintained a relapse-free clinical status for at least 18 months post-thyroidectomy.


Al‐Harake A, Dandache I, Moukadem H, et al. Malignant carcinoma and skin melanoma neoplasms concomitantly in the thyroid. Clin Case Rep. 2021; 9(9):e04790. doi:10.1002/ccr3.4790