Curious Residents of the Thyroid Gland: Two Case Reports of Colorectal Carcinoma Metastasis by Fine-Needle Aspiration Diagnosis

Abstract

Background: The most frequent metastases to the thyroid originate in the kidney, lung or breast. Colorectal adenocarcinoma represents less than 4% of metastases to the thyroid gland. Solitary metastases of colorectal cancer with no other manifestation of disseminated cancer disease are exceedingly rare. Within the Bethesda Classification for Reporting ­Thyroid Cytopathology, metastases are included in Diagnostic Categories “Suspicious for Malignancy” and “Malignant.” Cases: We present 2 cases of colorectal adenocarcinoma metastatic to the thyroid gland, diagnosed by fine-needle aspiration (FNA). One metastasis occurred in normal thyroid parenchyma; the other was a tumour-to-tumour metastasis into a follicular carcinoma of the thyroid. The latter is the first published tumour-to-tumour metastasis of a colorectal carcinoma in the thyroid from which both components were diagnosed by FNA. Conclusion: Diagnosing a metastasis to the thyroid is challenging. On FNA, a dual cell population should raise suspicion. Immunocytochemical and molecular analysis may be helpful. Clinical information is essential in guiding specific ancillary technique panels in scant cellular material.

Metastases to the Thyroid Gland: What Can We Do?

“…The average age of CRC patients with thyroid metastasis was 61 years, which was similar to that of CRC patients, and the average interval between the diagnosis of primary tumor and metastases to the thyroid gland was 51 ±31 months, while the average survival time of CRC patients with thyroid metastasis was only 11.3 months [ 37 ]. FNAB usually shows two different types of cells: thyroid and colorectal [ 38 , 39 ]. Kumamoto et al found that the most common site of origin (excluding the rectum) in patients with thyroid metastasis of CRC was the right ascending colon [ 40 ].…”

“…GATA-3, estrogen, and progesterone receptors are helpful in diagnosing the origin of breast cancer [ 4 , 65 ]. CRC cells are positive for CK20 and CEA but negative for thyroglobulin, calcitonin, and TTF-1 [ 38 , 39 ], which is helpful for the diagnosis of metastases to the thyroid gland of CRC origin. In addition, in an autopsy study on secondary thyroid tumors released in 2019, the immunohistochemical results of the above four most common primary tumors were reviewed and analyzed in detail [ 5 ] ( Table 1 ).…”

The value of core needle biopsy in the diagnostic workup of a [18F]FDG-PET positive thyroid metastasis from colorectal cancer

“…It has to be emphasized that reliable data both for direct comparison of core needle biopsy and fine needle punctuation, and reliability of both methods in secondary malignancies of the thyroid gland are still missing. In two case reports, the diagnosis of colorectal cancer metastases in the thyroid was guided by fine needle aspiration [5], in other cases it was definitely confirmed by operative resection.…”

Metastatic rectal cancer to papillary thyroid carcinoma: a case report and review of literature

“…The first documented case of mCRC to a primary thyroid neoplasm was described by Kameyama in 2000 [3]. Of the nine cases of mCRC to the recipient thyroid neoplasm reported, 2 the recipient thyroid tumors were follicular adenomas [3,5], 1 was Hürthle cell carcinoma [4], 4 were papillary carcinomas [6, 7, 9], 1 was medullary carcinoma [8], and 1 was follicular carcinoma [10]. Our literature review found that the interval between diagnosis of primary CRC and its metastasis to a thyroid neoplasm was in a range of 18 months to 9 years, mainly after curative treatment of the first diagnosis; only 1 case was detected synchronously with the primary malignancy, metastasis to a thyroid follicular adenoma as the initial presentation of a colonic adenocarcinoma [5].…”

“…And furthermore, rectal cancer to primary thyroid neoplasm metastasis, a tumor-totumor metastasis, is extremely rare. Up to date, only eight documented cases of mCRC to primary thyroid neoplasm metastasis were reported [3][4][5][6][7][8][9][10]. We report here a case of metastatic rectal adenocarcinoma to the papillary thyroid carcinoma and review the related literature on tumor-totumor metastasis of CRC in the thyroid gland.…”