Occult Papillary Thyroid Carcinoma Presenting with Bilateral Paratracheal Neck Masses – A Case Report and a Diagnostic Challenge
Emmeline Elaine L. Cua, MD, Rey Benjamin I. Joson, MD, Reynaldo O. Joson, MD, MSc Surg
2019
Abstract
A case of an occult papillary thyroid carcinoma presenting with bilateral paratracheal masses in a 71-year-old Filipino female with diagnostic challenges is being reported to raise awareness among Filipino physicians of this rare entity and also to promote efficient diagnostic approach. The patient, with past history of pulmonary tuberculosis, presented with bilateral big nodular paratracheal neck masses, initially palpated to be bilateral nodular thyroid masses for which a multiple colloid adenomatous goiter was suspected. However, after an ultrasound was done, the big nodular paratracheal neck masses turned out to be outside the thyroid gland and the thyroid gland was reported to have a 0.5 cm nodule on the upper pole of the right thyroid lobe. A right papillary thyroid carcinoma with bilateral neck node metastasis was primarily suspected. Secondary clinical diagnosis was tuberculosis lymphadenopathy on the neck with a colloid adenomatous nodule on the right thyroid lobe. A needle biopsy was done on the bilateral neck masses which revealed papillary thyroid carcinoma. Intraoperatively, before proceeding to do a thyroidectomy, the thyroid gland was grossly normal with no nodule palpated which led to an uncertainty whether the preoperative diagnosis of thyroid carcinoma was correct. However, on intraoperative evaluation of the bilateral neck masses, which grossly were lymph nodes, there was note of infiltration of the internal jugular veins. With preoperative needle biopsy of papillary carcinoma, an occult thyroid carcinoma with bilateral neck nodal metastases was thereby assumed. A total thyroidectomy with bilateral modified neck dissections was done. After the procedure, the whole thyroid gland was meticulously serially cut to look for occult thyroid carcinoma. Two 1-mm whitish nodules each were seen on the medial aspects of the right and left thyroid lobes and one 4-mm whitish nodule on the isthmus. All of these turned out to be thyroid microcarcinomas on histopathology. The bilateral neck nodes also contained papillary thyroid carcinomas. The patient underwent adjuvant radioactive iodine therapy after the operation.
Keywords: Occult thyroid cancer, occult papillary thyroid carcinoma, papillary thyroid microcarcinoma
Introduction
Occult papillary thyroid carcinomas are primary thyroid cancers that are not clinically apparent. To be considered occult, size of the primary papillary thyroid carcinomas if detected should be less than 1.0 cm (1-4) Some authors would set the upper limit at 1.5 cm (1, 5-7). However, majority set it at one cm or less.
The incidence of occult thyroid carcinomas has been reported to be 0.3% to 35% of all thyroid cancers (8, 9). The incidence of occult papillary thyroid carcinomas has been reported to be 7 to 25% of all papillary thyroid carcinomas (10, 11).
Lang (12), in 1988, in a sequence of 1,020 autopsies in a two-year period, found 63 or 6.2% occult thyroid cancers, the greatest diameters ranged between 0.5 and 10.5 mm. All but one of the 63 occult thyroid cancers were papillary type. Multicentricity was found in 46% and regional lymph node metastasis in 14%.
They are different kinds of clinical presentations of occult papillary thyroid carcinomas, one of which is with clinically apparent nodal metastasis where the cytologic or histologic diagnosis of papillary thyroid carcinoma in the metastatic foci leads one to suspect or to look for the occult carcinoma in the thyroid gland proper. Such kind of presentation of occult papillary thyroid carcinoma is uncommon considering the overall incidence of occult papillary thyroid carcinomas of 6% (12) and reported incidence of concomitant regional lymph node metastasis ranging from 14% (12) to 17.8% (13, 14).
In the Philippines, there are no formal data and no published reports on the frequency of occult papillary thyroid carcinoma as well as on occult papillary thyroid carcinomas with nodal metastasis.
This paper reports on a Filipino patient presenting with bilateral paratracheal masses which turned out to be metastatic papillary thyroid carcinoma associated with 3 microcarcinomas in the thyroid gland proper.
The objectives of this reporting are one, to raise awareness among the Filipino physicians of such a possibility of bilateral paratracheal masses coming from microcarcinomas in the thyroid gland and two, to discuss the challenges faced by a clinician, especially the surgeon, in making efficient approach to diagnosis.
The Case
A 71-year-old Filipino female consulted in February 2019 because of neck masses which were noted four years prior. There were no associated symptoms. On initial examination, there were multiple non-fixated nodules, averaging 2-cm in size, at the right and left paratracheal areas spanning from the level of the thyroid cartilage to just above the clavicles. On palpation, the multiple masses seemed to move with deglutition for which a thyroid disorder was suspected. There were no masses in other parts of the body such as axillae and inguinal areas to suggest a lymphoma. There was a past history of treatment of pulmonary tuberculosis 15 years prior. The primary clinical diagnosis given was multiple colloid adenomatous goiter. The secondary clinical diagnosis was tuberculous cervical lymphadenothies.
An ultrasound of the neck as well as chest radiograph were requested. Chest radiograph showed infiltrates on the bilateral upper lung fields. Ultrasound of the neck showed a 0.5 cm nodule on the upper pole of the right thyroid lobe with multiple bilateral neck nodes. The thyroid nodule seen on ultrasound was not palpable. With these additional data, the primary clinical diagnosis given was changed to thyroid carcinoma with bilateral neck node metastases. The secondary clinical diagnosis was tuberculous cervical lymphadenothies with colloid adenomatous nodule on the right thyroid lobe.
A needle biopsy was done on the neck masses. A sample was gotten on the right and another on the left. Results showed papillary carcinoma. With the needle biopsy result, the pretreatment diagnosis was changed to occult papillary thyroid carcinoma with bilateral neck node metastases. A neck exploration and possible complete thyroidectomy and bilateral modified radical dissection was planned.
On operation, after exposing the thyroid gland, it was meticulously palpated. The 0.5 cm right thyroid nodule reported on ultrasound was not palpated. At this point in the operation, a question was raised whether an occult papillary thyroid carcinoma was the true diagnosis. Exploration of the clinically palpable neck masses was done. They were deemed to be lymph nodes located along the internal jugular veins. There were no hemorrhagic lymph nodes that were suggestive of papillary carcinoma nodal metastasis. However, on both sides, some nodes were infiltrating the internal jugular veins. With this intraoperative evaluation of the neck nodes, a diagnosis of occult papillary thyroid carcinoma with bilateral neck node metastases was maintained. A total thyroidectomy and bilateral modified radical neck dissection with excision of the walls of internal jugular veins that had tumor infiltrations were done.
Immediately after the operation, the whole thyroid gland was meticulously examined and sliced serially to look for occult papillary carcinoma or carcinomas. A 4-mm cream white solid nodule was found on the isthmus and two 1-mm whitish solid nodules were each found on the medial aspect of the right and left thyroid lobes. (see Figs. 1 and 2) The 0.5 cm right thyroid nodule was not found.
Histopathology report confirmed the findings of the multifocal papillary microcarcinomas, conventional and follicular variants, in the abovementioned areas. The 0.5 cm nodule finding on ultrasound was not reported. The bilateral neck nodes were reported to contain papillary carcinomas.
Patient underwent radioactive iodine therapy a month after operation. She will be followed up for cancer surveillance.
Discussion
The term “occult thyroid carcinoma” was used, for the first time, in 1955 (15). It defined the thyroid cancer, with or without local metastases, which was identified after final histology (16).
Occult thyroid carcinoma and occult papillary thyroid carcinoma have various definitions in the literature (1).
In 1997, Moosa and Mazzaferri defined “occult thyroid carcinoma” as an “impalpable thyroid carcinoma that is generally smaller than 1.0 cm” (2). Stedman’s Medical Dictionary in 2006 defined “occult papillary carcinoma of the thyroid” as microcarcinoma of the thyroid or microscopic papillary carcinoma of the thyroid, usually well encapsulated and measuring less than 5 mm in diameter (17).
A combination is used in the World Health Organization classification system, where papillary thyroid microcarcinoma is defined as “papillary carcinoma measuring 1.0 cm or less in maximal diameter while other clinico-pathological features, such as metastasis to regional lymph nodes and/or distant organs as well as extrathyroid extension, are not considered” (3,4)
Shaha (5) and other authors (6,7) are using a broader definition for papillary thyroid microcarcinoma, 1.5 cm or less. Majority of the authors, however, are using 1 cm and less for occult papillary thyroid carcinomas. Recently, in 2018, Gong et al (18) from China are proposing using 8 mm as the cut-off size for occult papillary carcinomas. In an analysis of 1176 consecutive cases, they concluded that due to more aggressive behavior and poorer prognosis in larger tumor size (>8.5 mm), a tumor size ≤8.5 mm in diameter may be favorable to discriminate papillary thyroid microcarcinomas from papillary thyroid carcinomas and aid the selection of optimal management.
Occult thyroid carcinomas can be occult papillary and occult follicular carcinomas (19, 20). Occult papillary carcinomas are more common than occult follicular carcinomas. The reported incidence of occult papillary carcinomas is 7 to 25% of all papillary thyroid carcinomas (10, 11) while that of occult follicular carcinomas is 3-4% (21, 22).
The terms occult thyroid carcinoma and papillary microcarcinoma could be considered synonyms in the majority of clinical situations (1,4). This paper will focus on occult papillary thyroid carcinoma or papillary microcarcinoma.
They are different kinds of clinical presentations of occult papillary thyroid carcinomas (OPTC). Boucek (1) mentioned four groups or categories.
The first group comprises patients with thyroid carcinoma or microcarcinoma incidentally found in the thyroid gland after total thyroidectomy for benign disease or at autopsy.
The second group comprises of patients with incidentally detected OPTC on imaging studies, mainly ultrasonography, and evaluated by fine needle aspiration biopsy (FNAB).
The third group comprises of patients with clinically apparent metastases of thyroid carcinoma, where the primary tumor is not detectable before surgery and microscopic tumor – microcarcinoma is found in the final histological specimen.
The fourth group comprises of patients with thyroid cancer localized in ectopic thyroid tissue with clinical symptoms or with apparent metastases.
Liu et al (23) proposed a fifth group which comprises of patients with clinical apparent metastases of thyroid carcinoma but the primary carcinoma could not be found by pathological examination of the thyroid gland.
There are no formal data on the relative frequencies of the four or five groups of occult thyroid papillary carcinoma. Extrapolation from various current reports in the literature shows the first group to be the most common followed by the second then the third group. The fourth and fifth groups are not common. The rampant use of ultrasonography and fine needle biopsy nowadays contribute to its second ranking in frequency. In the third group with clinically apparent metastasis, neck node metastasis is more common than distant metastasis.
Woolner (16) n 1960 reported that of 140 occult papillary carcinomas treated surgically at the Mayo Clinic over a 30-year period, 58 were associated with nodal metastasis and 82 were found incidental to thyroid operations for other conditions. None had distant metastasis.
Ito (9) reported in 2008 that between 1990 and 2004, 5400 patients underwent surgery for papillary thyroid carcinoma at Kuma Hospital, Japan. Seventeen (0.3%) were regarded as having occult papillary carcinoma. Clinically apparent node metastasis was detected in the lateral compartment in 16 patients and in the mediastinal compartment in 1 patient.
The patient in this case report belongs to the third group, one presenting with clinically apparent nodal metastasis which led to the discovery of the occult papillary thyroid carcinomas.
The patient initially presented as a diagnostic challenge when multiple paratracheal nodules were palpated in a background of being treated before for pulmonary tuberculosis. The paratracheal masses, because of their adjacency to the trachea, moved with deglutition leading one to suspect multiple colloid adenomatous goiter (MCAG) as this is very common in the Philippines. Because of the past history of pulmonary tuberculosis, tuberculous cervical lymphadenopathy was a differential diagnosis.
After the ultrasound revealed the bilateral paratracheal masses were neck nodes rather than thyroid nodules but with a 0.5 cm nodule on the right upper thyroid lobe, the initial clinical diagnosis of MCAG was changed to thyroid cancer with bilateral neck node metastasis. The result of fine needle aspiration biopsy which showed papillary carcinoma firmed up the second diagnosis which became the pretreatment diagnosis.
On initial intraoperative evaluation, the whole thyroid gland was grossly normal. The 0.5-cm nodule seen on ultrasound was not palpated. These initial intraoperative findings presented another round of diagnostic challenge, questioning whether there was an occult carcinoma or not and whether a thyroidectomy should be done. The surgeons proceeded to evaluate the paratracheal nodes. The presence of infiltration of the bilateral internal jugular veins in the background of a needle biopsy result of papillary carcinoma led to the surgeons to make an intraoperative diagnosis of neck node metastasis from an occult papillary thyroid carcinoma. Thus, the surgeons decided to do a total thyroidectomy and bilateral modified radical neck dissection with the plan to examine the thyroid gland closely after its removal. The result of the closed examination of the removed thyroid gland showed three foci of papillary microcarcinomas which were confirmed in the microscopic examination.
Conclusion
Reported is a case of a 71-year-old Filipino female presenting with bilateral paratracheal masses which turned out to be metastatic papillary thyroid carcinomas associated with 3 microcarcinomas in the thyroid gland proper. Approaches and challenges in clinical, paraclinical and intraoperative diagnoses were discussed. Careful intraoperative evaluation of the thyroid gland and the neck nodes plus a cytologic diagnosis of papillary carcinoma in the metastatic foci will facilitate diagnosis of an occult papillary carcinoma in the thyroid gland proper. Total thyroidectomy followed by a meticulous examination of the gland is done to search for the occult papillary carcinoma in the thyroid gland proper. The nodal metastases are treated accordingly, here a modified radical neck dissection was done. After surgery, radioactive iodine treatment was given.
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Fig 1. Thyroid after total thyroidectomy (center) and bilateral neck nodes.

Fig 2. Showing the microcarcinomas in the isthmus and medial aspect of the right and left thyroid lobes.
Links:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4056144/
Our experience with papillary thyroid microcancer