|Year : 2013 | Volume
| Issue : 3 | Page : 104-107
Fine needle aspiration cytology of thyroglossal duct cyst: Diagnostic pitfalls and a study of 14 cases
Shirish S Chandanwale, Archana C Buch, Kaur R Chawla, Pratik U Mittal
Department of Pathology, Padm. Dr. D. Y. Patil Medical College, Pimpri, Pune, Maharashtra, India
|Date of Web Publication||6-Aug-2013|
Shirish S Chandanwale
Department of Pathology, Padm. Dr. D.Y. Patil Medical College, Pimpri, Pune, Maharashtra
Source of Support: None, Conflict of Interest: None
Objectives: To review the cytohistological features of 14 cases of thyroglossal duct cyst (TDC), to ascertain the role of fine needle aspiration cytology (FNAC) in the diagnosis and treatment, and to discuss the diagnostic pitfalls. Materials and Methods: FNAC of 14 patients of TDC diagnosed clinically and by ultrasound examination of neck was studied. Cytology features were correlated with histopathologic features. Results: Cytology smears showed most commonly few macrophages (n = 7), followed by polymorphonuclear leukocytes (n = 4). One case showed few small sheets and many dispersed follicular cells showing features suspicious of papillary thyroid carcinoma (PTC). Histopathology showed pseudostratified columnar and cuboidal epithelium (n = 6) in maximum cases and confirmed PTC in one case. Conclusion: Imaging techniques or FNAC alone is not adequate for pre-treatment assessment of all TDC cases. All TDC patients must be subjected to image-guided FNAC for early and accurate diagnosis of TDC carcinoma for timely clinical intervention.
Keywords: Aspiration cytology, papillary thyroid carcinoma, thyroglossal duct cyst
|How to cite this article:|
Chandanwale SS, Buch AC, Chawla KR, Mittal PU. Fine needle aspiration cytology of thyroglossal duct cyst: Diagnostic pitfalls and a study of 14 cases. Thyroid Res Pract 2013;10:104-7
|How to cite this URL:|
Chandanwale SS, Buch AC, Chawla KR, Mittal PU. Fine needle aspiration cytology of thyroglossal duct cyst: Diagnostic pitfalls and a study of 14 cases. Thyroid Res Pract [serial online] 2013 [cited 2017 Jul 26];10:104-7. Available from: http://www.thetrp.net/text.asp?2013/10/3/104/116136
| Introduction|| |
Thyroglossal duct cyst (TDC) is the most common developmental abnormality encountered in the neck. Though it is more frequently encountered in children, prevalence in adult population is 7%. It manifests as anterior midline neck mass between hyoid bone and mandible. Recurrence and potential for malignancy are the two main clinical problems. Reported incidence of malignancy in TDC is less than 1%.  The clinical presentation of thyroglossal duct carcinoma may be indistinguishable from that of benign TDC. It may present with a rapidly enlarging neck mass. Preoperative diagnosis of TDC is required for more accurate and timely clinical intervention. In vast majority of cases, clinical examination, ultrasonography (USG) of neck, and fine needle aspiration cytology (FNAC) are adequate for pre-treatment assessment.  Very few reports describing the cytology of TDC have been published in the past. , In this article, the cytohistological features of TDC are discussed and diagnostic pitfalls are highlighted.
| Materials and Methods|| |
From May 2008 to June 2011, 14 patients of TDC diagnosed clinically and by ultrasound examination of neck were referred to the cytology department for FNAC. USG examination of neck in all patients showed midline cystic lesions measuring 1-4 cm in diameter, separate from the thyroid. Twelve patients had normal thyroid gland and two had multinodular goiter. None of the patients had cervical lymphadenopathy. Thyroid scan was performed in one case which showed a small cold area in the midline neck cystic mass and normal uptake of radioiodine in the thyroid gland. FNAC was performed using 23 gauge disposable needle. Smears prepared were air dried and stained with Leishman stain. Aspirate in 10 patients yielded watery, slightly hazy fluid, while in 4 patients, the aspirates were scanty blood-tinged fluids. All the patients were operated by Sistrunk procedure which involves en bloc removal of the cyst, including mid portion of the hyoid bone. Tissues were formalin fixed and paraffin processed. Sections were stained with hematoxylin and eosin (H and E). Postoperative follow-up was possible in nine patients and the duration ranged from 6 to 24 months.
| Results|| |
Ages of the patients ranged from 5 to 50 years, with M:F ratio of 1:2. Maximum number of patients (n = 10) were adults. The most common clinical presentation was nontender midline mobile mass which was either painless or painful. Size of the cysts ranged from 1.2 to 4.1 cm in diameter. Clinical and cytohistological profile of all 14 patients is given in [Table 1]. The commonest cytological feature of TDC was few macrophages (n = 7), followed by numerous polymorphonuclear leukocytes (n = 4) [Figure 1]a, few squamous cells (n = 3), colloid (n = 2), and mucinous material with occasional columnar cells (n = 1). One case showed few small sheets and dispersed follicular cells. Occasional sheet showed nuclear crowding and nuclear enlargement. Intranuclear cytoplasmic inclusions (INCI) [[Figure 1]b, thick arrow] and nuclear grooves (NG) [[Figure 1]b, thin arrow] were seen in a few nuclei [Figure 1]b. Papillary thyroid carcinoma (PTC) arising in TDC was suspected. The remaining aspirates (n = 13) showed no follicular cells. All the patients were operated by Sistrunk procedure. Histological examination showed cyst lining of pseudostratified columnar and cuboidal epithelium (n = 6) and transitional epithelium (n = 2). Squamous lining was not seen in any case. Cyst wall showed thyroid follicles (n = 8), lymphocytic inflammatory cells (n = 7), and cholesterol crystals (n = 1). In one TDC aspirate which showed follicular cells with atypical features, the surgical specimen received was a cyst measuring 1.2 × 0.6 × 0.6 cm, occupied by a small nodule of 0.6 × 0.6 cm [[Figure 2]a, thin arrow] with attached hyoid bone [[Figure 2]a, thick arrow]. Histological examination showed tumor attached to the cyst wall with true papillae [Figure 2]b, with oval to elongate nuclei having ground-glass appearance and psammoma bodies [[Figure 2]b, inset, arrow] Cyst wall and the adjacent tissue was free of tumor. A diagnosis of PTC arising in TDC was made. Duration of follow-up in nine patients ranged from 6 to 24 months. None of the patients developed complications.
|Figure 1: FNAC smears showing (a) neutrophils and (b) sheets of follicular cells with ING (thin arrow), INCI (thick arrow) (Leishman, × 400)|
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|Figure 2: (a) A specimen of TDC occupied by small nodule (thin arrow) with hyoid bone (thick arrow), (b) Microscopy shows TDC fibrous cyst wall occupied by PTC (H and E, × 100). Inset shows psammoma body (arrow) (H and E, × 400)|
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| Discussion|| |
TDC is the most common nonodontogenic cyst, with the prevalence being 7% of the adult population.  Clinically these lesions can be confused with brachial cleft cyst, colloid cyst, or lymphoepithelial cyst.  CT scan or USG decides the origin of the cyst. USG in all our 14 cases helped in diagnosing TDC as it was separate from thyroid. Cytological features of TDC have been described in a few studies where the authors found either abundant colloid most often with ciliated columnar epithelium or few mature squamous cells or columnar cells with very rarely follicular cells in TDC aspirates. ,,, Cytological findings in our study were partly in accordance with other authors. Out of 14 cases, few squamous (n = 3) and columnar (n = 1) cells were seen in 4 cases only. Colloid was seen in two cases. Macrophages (n = 7) were most commonly seen on TDC aspirates in our study. So, we feel cytological features of TDC are variable and may not be diagnostic of TDC. Numerous neutrophils in four cases suggested acute infection. Squamous cells (n = 3) in TDC aspirates were possibly because of contamination from skin or trachea. 
Histological examination of the resected 13 TDC specimens showed cyst lining of pseudostratified columnar and cuboidal epithelium (n = 6) and transitional epithelium (n = 2). Squamous lining was not seen in any case. Cyst wall showed thyroid follicles (n = 8), lymphocytic inflammatory cells (n = 7), and cholesterol crystals (n = 1). These findings were in accordance with other authors. ,, Marianowski et al, observed recurrence rate of 50% in recurrent infections of TDC. All four patients were treated preoperatively with effective antibiotics. None of the patients developed recurrence during the follow-up period.
One case in which PTC arising in TDC was suspected on aspiration was a 22-year-old female. TDC aspirate showed few small sheets and dispersed follicular cells, and few nuclei showed nuclear grooves and intranuclear cytoplasmic pseudoinclusions [Figure 1]b. PTC arising in TDC was suspected on FNAC. Histological examination showed tumor attached to the cyst wall with true papillae [Figure 2]b, with oval to elongate nuclei having ground-glass appearance and psammoma bodies [[Figure 2]b, inset]. Cyst wall and the adjacent tissue was free of tumor. Diagnosis of PTC arising in TDC was confirmed. If malignancy has spread beyond the cyst wall, total thyroidectomy followed by suppressive doses of eltroxin are recommended. Patient has been on follow-up since 20 months and so far has not revealed any evidence of recurrence.
Carcinomas arising in TDC are usually of two types: thyrogenic carcinoma and squamous carcinoma. Thyrogenic carcinoma most often arises from thyrogenic rests in duct or cyst wall, and squamous carcinomas arises from the metaplastic columnar epithelial cells. Papillary carcinomas are common and usually seen in younger women.  TDC carcinomas are usually asymptomatic and not suspected preoperatively in most instances. Imaging techniques such as ultrasonography and CT scan alone are usually unable to diagnose malignant disease in TDC preoperatively.  Although the diagnostic criteria of PTC on FNAC have been defined, diagnostic pitfalls in giving definitive diagnosis of PTC arising in TDC are very common. FNAC yielded correct results in only 50-60% of cases. , Definitive diagnosis of PTC could not be made in this case for the following reasons: smaller size of the lesion, suboptimal sample, and dilution by cystic fluid leading to hypocellular smears. So, we feel all TDC cases shall be subjected to USG-guided FNAC for early and accurate diagnosis of PTC.
| Conclusion|| |
So, we conclude that FNAC findings in TDC are variable, but when correlated with clinicoradiological findings, accurate diagnosis can be made in most cases. But imaging techniques or FNAC alone may not be adequate for pre-treatment assessment in all cases of TDC. Apart from imaging studies, all TDC patients must be subjected to image-guided FNAC for early and definitive diagnosis of carcinoma. Neutrophils in TDC aspirates need treatment with effective antibiotics preoperatively to prevent recurrence.
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[Figure 1], [Figure 2]