Tumor-to-tumor metastasis is extremely rare in the thyroid glands, and only seven cases of lung carcinoma metastasizing to thyroid tumors have been reported in the literature. We report another two cases of lung carcinoma metastasizing to thyroid neoplasms and review of the literature. The first case was a 64-year-old man presenting with neck mass, hoarseness, and easy choking for 2 months. Image studies showed several nodular lesions within bilateral thyroid glands. A histological examination after radical thyroidectomy revealed lung small cell carcinoma metastasizing to a thyroid follicular adenoma. The second case was a 71-year-old woman with a history of lung adenosquamous carcinoma. The PET/CT scan showed left lower lung cancer and a hypermetabolic area in the right thyroid lobe, highly suspicious for malignancy. Radical thyroidectomy and left lung lobectomy were performed, and the thyroid gland revealed lung adenosquamous carcinoma metastasizing to a papillary thyroid carcinoma.
The thyroid gland is an uncommon site for metastatic tumors, and most thyroid gland tumors are primary. The overall incidence of metastatic thyroid gland tumors is ranging from 1.4 to 3% [
A 64-year-old man, who had no past history of major disease, presented with neck mass, hoarseness, and easy choking. Fine needle aspiration of bilateral thyroid glands was performed and cytology showed plenty of single or cohesive tumor cells, and anaplastic carcinoma was suspected. Image studies revealed several nodular lesions with strong heterogeneous enhancement within bilateral thyroid glands. The patient received a radical thyroidectomy. On gross examination, the left thyroid gland was
(a) Within the encapsulated follicular adenoma is an abrupt transition to a morphologically distinct neoplasm (magnification ×40). (b) Metastatic carcinoma is arranged in sheets with hyperchromatic nuclei and scanty cytoplasm infiltrating the follicular adenoma (magnification ×200). (c) The metastatic carcinoma is negative for thyroglobulin, while the adenoma is strongly positive (magnification ×100). (d) Synaptophysin is strongly positive in the metastatic carcinoma (magnification ×200).
A 71-year-old woman presented with a pulmonary mass diagnosed as adenosquamous carcinoma based on biopsy and received adjuvant chemotherapy. Three months later, PET/CT scan revealed left lower lung cancer and a hypermetabolic area in the right thyroid lobe, highly suspicious for malignancy. Fine needle aspiration of right thyroid gland was performed and cytology showed groups of follicular cells with features of papillary thyroid carcinoma. The patient received a radical thyroidectomy and left lung lobectomy. On gross examination, there was a tumor measuring
(a) Within the papillary carcinoma is an abrupt transition to a morphologically distinct neoplasm (magnification ×40). (b) Metastatic carcinoma is arranged in nests with large nuclei, nucleoli, and abundant clear-to-eosinophilic cytoplasm (magnification ×200). (c) Napsin-A is shown to be positive in the metastatic carcinoma (magnification ×200). (d) Thyroglobulin is negative in the metastatic carcinoma, while being strongly positive in papillary carcinoma (magnification ×100).
Metastatic disease to thyroid gland is uncommon, with reported incidence ranging from 1.4 to 3% of all patients who undergo surgery for suspected cancer in the thyroid gland [
Metastasis to a thyroid neoplasm—tumor-to-tumor metastasis—is extremely rare, and only about 31 cases have been reported in the literature [
In the 9 cases of lung carcinoma metastasizing to thyroid tumor (including our 2 cases, Table
Lung carcinoma metastasizing to thyroid tumor: the cases reported in the literature.
Authors | Age | Gender | Receiving thyroid neoplasm | Lung carcinoma | Interval |
---|---|---|---|---|---|
Akamatsu et al. [ |
46 | Female | Follicular adenoma | Well-differentiated adenocarcinoma | 4 months |
Hashimoto et al. [ |
60 | Female | Follicular variant of papillary thyroid carcinoma | Adenocarcinoma | Synchronous |
Kameyama et al. [ |
51 | Male | Follicular adenoma | Moderately differentiated adenocarcinoma | Autopsy |
Mori et al. [ |
54 | Male | Follicular variant of papillary thyroid carcinoma | Poorly differentiated adenocarcinoma | Autopsy |
Stevens et al. [ |
65 | Male | Follicular adenoma | Poorly differentiated carcinoma | 2 months |
Mizukami et al. [ |
75 | Female | Follicular adenoma | Poorly differentiated carcinoma | Autopsy |
Baloch and LiVolsi [ |
75 | Female | Follicular variant of papillary thyroid carcinoma | Small cell carcinoma | 2 years |
Wey (present case 1) | 66 | Male | Follicular adenoma | Small cell carcinoma | Synchronous |
Wey (present case 2) | 72 | Female | Papillary thyroid carcinoma | Adenosquamous carcinoma | 3 months |
Tumor-to-tumor metastasis should be considered when a distinct histological pattern is encountered in a tumor or in a patient with previous history of malignancy. Preoperative diagnosis of a primary thyroid tumor versus metastatic disease is difficult because of similar radiological findings and clinical presentations [
The treatment of metastatic disease is dependent on the stage and grade of the primary tumor, extension of the thyroid lesion, and the general condition of the patient [
In conclusion, tumor-to-tumor metastasis in thyroid gland is exceedingly rare, and it should be considered in patients with a thyroid mass and previous history of malignancy. The abnormal thyroid glands with goiter or tumors might be more susceptible to metastatic malignancies because of a decrease in oxygen and iodine content. Lung carcinoma is the second common primary tumor metastasizing to a thyroid neoplasm, and only about 7 cases have been reported in the literature. We present another two cases of lung carcinoma metastasizing to thyroid tumors. The distinction between primary and metastatic tumors is difficult in some cases. Careful histological examination and molecular and immunohistochemical studies are helpful for differential diagnosis.
An informed consent was provided by the patients.
The authors declare that there is no conflict of interests regarding the publication of this paper.