Original case by Yanery’s Agosto-Vargas, Madeleine Gutiérrez, José Hernán Martínez, MichelleMangual-Garcia, Coromoto Palermo, Sharon Vélez-Maymi, Luis Hernández-Vázquez, Samayra Miranda-Rodríguez, Alex González-Bossolo, Ernesto Solá-Sánchez, and Marianne Hernández-Negrón
CRITICAL REVIEW BY DR. OM J LAKHANI (ENDOCRINOLOGIST)
This is the case of a 33-year-old man without significant medical history who was incidentally diagnosed with a right neck cystic mass by computer tomography (CT) after a motor vehicle accident. Patient denied diaphoresis, palpitations, diarrhea, constipation, mood changes, or any other symptoms. Physical exam revealed a right-sided tender neck mass, without any other remarkable findings. He did not have history of neck irradiation, thyroid disease, or family history of thyroid cancer. Thyroid function tests were within normal limits (TSH: 1.5 IU/mL). Excisional biopsy of the neck mass reported metastatic, well-differentiated, thyroid papillary carcinoma within lymph node tissue. Pathologic description consisted of a nodular segment, tannish, rubbery specimen with attached membranous cystic tissue. The pathological specimen (lymph node) was distorted and had a well-defined cystic structure within it. While the cystic structure measured 2 cm × 1.5 cm × 1 cm, the lymph node measured 1.5 cm × 1 cm (Figure 2). Due to previous findings, he underwent total thyroidectomy with right neck dissection in order to rule out occult primary carcinoma of the thyroid. Histopathological findings revealed a normal thyroid gland without evidence of papillary thyroid carcinoma and sixteen right neck lymph nodes without evidence of metastasis. Thyroid pathology was meticulously reviewed, without any evidence of papillary thyroid carcinoma identified.
Q What is your impression of this case ?
It seems there is PTC present in a rare ectopic tissue present in the cervical region since the Eutopic thyroid gland has no evidence of thyroid cancer.
Q So this is a case of Papillary thyroid cancer (PTC) post thyroidectomy. Would you give post operative radioactive iodine in this case ?
All patients with PTC donot require radioactive iodine therapy post operatively. In all such cases a post-operative re-staging is done to classify the patient into Low risk, Intermediate risk and high risk.
Radioactive iodine therapy is indicated in those considered to have high risk according to American thyroid association (ATA) guidelines. The following are considered to be high risk
- Gross extrathyroidal extension
- Incomplete surgery / gross residual disease
- Distant metastasis
- Post op Tg suggestive of distant metastasis
It is considered in those with ‘intermediate’ risk and not indicated in those with low risk.
Q In which risk category would you classify this patient ?
It is difficult to classify the patient according to ATA classification since there is presence of PTC in the ectopic thyroid gland but not in the eutopic thyroid gland. Also there is no evidence of lymph node metastasis. Hence it would be difficult to classify this patient and hence consider the patient as having intermediate risk and CONSIDER radioactive iodine therapy for this patient.
Q How will you follow up this patient ?
I would not start the patient on LT4 and follow the patient after 6-8 weeks with TSH. If TSH is >30 , patient sent for Radioactive iodine ablation with 30 mCi.
After surgery, thyroid hormone replacement was started. One month after procedure, thyroglobulin was 133.61 ng/ml (1.15–130.77 ng/ml) and thyroglobulin antibodies were 11.8 uU/ml (negative, less than 45 uU/ml).
Q What is interpretation of these reports ?
We donot know if the Tg is stimulated or unstimulated, however in either case Tg is very high and needs evaluation. This would be classified as ‘Biochemical incomplete response’ or ‘Structural incomplete response’ depending on the presence or absence of any remnant tissue in the neck. So I would order a neck ultrasound from an experienced radiologist as my first line of approach.
In retrospect it suggests that the authors should have considered Radioactive iodine ablation post operatively. However, we have an advantage of hind sight and as described above the post operative staging according to ATA was tricky to begin with.
Thyroid scintigraphy reported functional thyroid remnants at the right thyroid bed. Ultrasonography evaluation revealed hypoechoic foci within the thyroid beds bilaterally, likely secondary to postsurgical granulation tissue versus residual thyroid tissue.
A right, level 2A lymph node seen measured 2.1 × 1 cm with loss of normal lymph node morphology, without microcalcifications or internal increase in vascularity. Another lymph node at level 3 measured 2 cm × 0.7 cm × 8.7 cm, without worrisome features. Fine needle aspiration biopsy of the aforementioned nodules showed papillary thyroid carcinoma.
Q How will you restage this patient now ?
The patient now is re-staged as high risk.
Q What are the treatment options now ?
For residual disease in neck the options are close follow up, surgery and radioactive iodine ablation.
In Gross extensive residual disease surgery is the best option. For minimal residual disease surgery is indicated in cases where size of lateral nodes is >1.5 cm. In this case a repeat surgery for local disease would be a better option.
Final diagnosis was malignant transformation of heterotopic thyroid tissue. Whole-body scan showed functional thyroid tissue remnants in the thyroid bed with multiple enlarged neck lymph nodes. At that time, TSH was elevated (44.3 IU/mL) and free T4 was suppressed (0.58 ng/dl; normal value: 0.75–1.54 ng/dl). The patient was referred to nuclear medicine for radioiodine therapy. Radioiodine ablation 142.2 mCi was given. After appropriate cessation of hormone replacement therapy, whole-body scan showed no nodules uptake.
Q Why this approach is incorrect to an extent ?
Presence of considerable local disease it is difficult to judge and ablate distant metastasis. Hence ideally surgery would have been a better approach followed by Radioactive iodine ablation if needed. In the currently scenario there seems to be a false reassurance of absence of distant mets on a radioactive iodine pre-therapy scan. I would advice the authors for a close post operative follow up of this case.
- This is a rare case where PTC in an ectopic thyroid tissue that too in lateral neck region without evidence of malignancy in the eutopic thyroid.
- In cases where post-operative ATA staging is ambiguous, it is better to consider a higher stage than a lower stage.