Papillary Thyroid Cancer With Cutaneous Metastasis: A Case Report and Literature Review

ABSTRACT Background Cutaneous metastasis of papillary thyroid carcinoma is rare, which may present as slowly growing nodules, erythematous papules, or ulcerative nodules. The pathophysiological mechanisms of skin metastasis in thyroid cancer remain unclear. Skin metastasis of thyroid papillary carcinoma represents a poor prognostic factor in previous studies, and whether there exist relative genes still needs to be further investigated. Summary Eight years after a radical surgery for left‐sided thyroid cancer, a 29‐year‐old female presented to our dermatology department after discovering a patch of hyperpigmentation on the right side of her neck for 2 years. The dermatologist performed a biopsy of the neck skin mass under local anesthesia, and the gross specimen consisted of a piece of skin tissue measuring 0.4 cm × 0.3 cm × 0.3 cm, with a gray‐black area of 0.4 cm on the surface. Microscopic examination, along with the clinical history, suggested metastasis of papillary thyroid carcinoma. Further immunohistochemical analysis showed results consistent with metastasis of papillary thyroid carcinoma, with tumor cells expressing TTF‐1 (positive), TG (−), Ki67 (−), PAX‐8 (+), GCDFP (−), ER (−), PR (20%), and GATA‐3 (−). Conclusion Skin metastases account for a relatively small proportion of metastatic thyroid cancer and can be easily misdiagnosed. Patients with skin lesions, especially in the head and neck area, that appear during the follow‐up of thyroid cancer should be carefully selected and diagnosed.