Solitary posterior triangle neck mass as the rare sole presentation of papillary thyroid carcinoma

Introduction: Papillary thyroid carcinoma is the most common differentiated thyroid malignancy. It offers good prognosis and the presentation is usually consistent with an enlarged thyroid, mostly solitary nodule which biochemically euthyroid and radiologically normal appearance. On rare occasions, the thyroid gland enlargement can present together with multiple neck lymphadenopathy. Case report: We report a case of middle aged man presented with a posterior neck mass without any other symptom. Histopathology report of the excised mass confirmed the diagnosis of, papillary thyroid carcinoma which warranted total thyroidectomy and neck dissection.


Introduction:
Presence of thyroid follicular cells in fine needle aspiration for cytology (FNAC) of lateral neck swellings with benign-appearing thyroid tissue in lymph node should be evaluated with extreme caution.Excisional biopsy is necessary even if follicular cells are benign looking.If follicular cells are found in lymphoid background, the diagnosis is always metastatic papillary thyroid carcinoma (PTC).Owing to its propensity for lymphatic spread, cervical lymphadenopathy can be present without the primary tumour being evident 1 .

Case report:
A 33-year-old Malay male, an army was referred for a right upper neck swelling which was slowly increasing in size over nine months duration.The mass did not cause any obstructive or compressive symptom.There was no hoarseness and any nasal complaint.He denied any contact with tuberculosis patient.He was free from any constitutional symptoms such as loss of weight or appetite, chronic cough or any swelling elsewhere in the body.
Clinical examination revealed a 6x5 cm neck swelling located at the right posterior triangle (level V).It was firm and non-tender, mobile in all directions, not attached to underlying structures or to the overlying skin which appeared normal.The mass did not change its size and position during both acts of respiration and deglutition.There was no other swelling either at midline or lateral to the mass, at all levels of the neck.Oral cavity and oropharyngeal examinations were normal.Nasoendoscopy, otoscopy and laryngoscopy also revealed normal findings.
In view of suggestive of thyroid follicular cells in FNAC smears, metastatic thyroid carcinoma could not be ruled out.As the ultrosonography revealed no abnormality of the thyroid gland, computed tomography and radionuclide imaging of thyroid gland were requested.However, all of the radiological investigations gave no extra information besides normal appearance and activity of the thyroid (Figure 2).Excision biopsy of the only mass was performed.Right level V cystic mass sized 4x5 cm was found located below posterior border of sternocleidomastoid muscle.There was no adhesion to the adjacent structures and no other lymph node seen.It was a well capsulated cystic mass, in which 4 cc of dark coloured fluid was aspirated.Our intraoperative finding diagnosis was branchial cyst.
The mass was sent for histopathological examination.It was interpreted as metastatic papillary thyroid carcinoma (Figure 3).
Several investigations which include sputum for acid fast bacilli were negative, chest radiograph was normal and Mantoux test was insignificant.Ultrasonography of the neck revealed an enlarged right cervical lymph node with necrotic changes.FNAC showed normal thyroid follicles with no evidence of malignancy or any lymphoid background appreciated (Figure 1).

Discussion:
The involvement of cervical LN in PTC may be the first manifestation of the disease.However, in our case, the pre-excision FNAC showed only thyroid follicular cells without features of lymph node background appreciated.Thus the diagnosis of ectopic or lateral aberrant thyroid was also entertained.The cystic metastasis in the lateral neck lymph node of a PTC may mimic a branchial cyst 2 .
The next step to confirm the diagnosis is by excision of the mass.Excision biopsy of any lateral neck cyst is essential in cases where results of FNAC and ultrosonography are inconclusive 3 As demonstrated in our case, the specimen confirmed the presence of metastatic thyroid carcinoma which warranted total thyroidectomy.Even the thyroid is not enlarged; the primary focus could be within the normal sized gland and be normal on radionuclide activity scanning.Intra-thyroidal PTC may be minute and careful examination of many sections may be required.In rare occasions, PTC primary site may disappear and might not be seen in thyroid.
A point to note is that a mass located medial to jugular vein, if contain benign thyroid tissue within the capsule or immediately subcapsular, can be from thyroid inclusion or sequestered thyroid 4 .The thyroid tissue which is found lateral to the carotid sheath and jugular vein can be considered as lateral aberrant thyroid+.However, most of the reported lateral aberrant thyroid cases are not fulfill this definition 6 .
LiVolsi has specifically stated that normal appearing thyroid tissue anywhere within lymph nodes, lateral to the jugular vein represents metastatic papillary thyroid carcinoma, and the term lateral aberrant thyroid tissue should not be used for those lesions 7 .Another study reported a case of Following the result, total thyroidectomy and right modified radical neck dissection type III was commenced.Gross specimen of 39 g thyroid gland was removed, together with fat pads in all levels of lymph node (Figure 4    The final result of PTC was revealed and out of 12 samples of LN histologically examined, only one at paratracheal was positive of metastasis.
follicular thyroid tissue was found in a lymph node lateral to the carotid sheath in the presence of a thyroid gland which was histologically free of cancer 8 .

Figure 4 :
Figure 4: Both right lobe (upper specimen) and left lobe contained grey white area which signified solid component suggestive of primary lesions.

Figure 5 :
Figure 5: Section from gray white area of left lobe showed macropapillary structures which confirmed the diagnosis (x4)