Fine needle aspiration biopsy of neuroendocrine breast carcinoma metastatic to the thyroid. A case report

BACKGROUND: Tumors showing neuroendocrine differentiation arise in a wide range of organs, and metastatic neuroendocrine tumors may be difficult to differentiate from primary tumors. This report describes an unusual case of metastatic breast carcinoma with neuroendocrine differentiation that presented as a solitary thyroid nodule. The diagnosis was made by fine needle aspiration biopsy (FNAB). CASE: A 52-year-old woman presented with a thyroid nodule and bilateral enlarged supraclavicular fossa lymph nodes. FNAB revealed a neuroendocrine carcinoma. Further questioning revealed that the patient had had a breast carcinoma resected eight years previously. The diagnosis of metastatic neuroendocrine breast carcinoma was established by immunocytochemistry. The patient received antiestrogen therapy but subsequently developed skeletal metastases. CONCLUSION: Neuroendocrine carcinomas from various sites show similar cytologic features. In this case, a diagnosis of breast carcinoma metastatic to the thyroid was suggested by the clinical history and confirmed by FNAB with immunocytochemistry.     

Signet-ring follicular adenoma of the thyroid diagnosed by fine needle aspiration. Report of a case with cytologic description

BACKGROUND: Follicular cells of the thyroid may undergo squamous, oncocytic or clear cell metaplastic changes. Of these, the clear cell change with signet-ring formation is the most unusual, and follicular adenoma of the thyroid with signet-ring formation is extremely rare. We describe for the first time the cytologic features of a clear cell adenoma of the thyroid obtained by fine needle aspiration (FNA). CASE: A 48-year-old woman in a euthyroid state presented with a 2-cm, right-sided thyroid nodule. Smears obtained by FNA of the nodule revealed clusters of large signet-ring cells in a bloody background. The signet-ring cells were round to oval, with large cytoplasmic vacuoles and hyperchromatic, eccentric nuclei. Colloid in the background was very scanty. Histologic examination of the right hemithyroidectomy specimen revealed a signet-ring follicular adenoma. CONCLUSION: Lack of familiarity with signet-ring cell adenoma of the thyroid could lead to an erroneous diagnosis of metastatic signet-ring cell carcinoma.     

Isolated carcinoid tumor metastatic to the thyroid gland: report of a case initially diagnosed by fine needle aspiration cytology

BACKGROUND: Neuroendocrine tumor metastatic to the thyroid gland is rare and may be difficult to differentiate from primary thyroid neuroendocrine tumors, such as medullary thyroid carcinoma (M/ITC). This report describes an unusual case of bronchial carcinoid metastatic to the thyroid diagnosed by fine needle aspiration cytology (FNAC). CASE: A 42-year-old woman with an undiagnosed bronchial carcinoid tumor presented to our clinic with a solitary nodule in the thyroid gland. FNAC of the nodule showed loosely cohesive groups of cuboidal tumor cells with scant, slightly granular cytoplasm; centrally located nuclei with a coarsely granular, salt-and-pepper chromatin pattern and inconspicuous nucleoli. Immunocytochemically the tumor cells were positive for neuron-specific enolase, chromogranin and synaptophysin and negative for thyroglobulin, calcitonin and carcinoembryonic antigen. The cytologic diagnosis of a metastatic neuroendocrine carcinoma was confirmed histologically. CONCLUSION: Metastasis to the thyroid gland may pose a diagnostic problem, particularly with tumors of neuroendocrine origin, as these have similar cytologic features in various organs. The correct preoperative cytologic diagnosis of metastatic carcinoid tumor in patients without a prior history of cancer and differential diagnosis with MTC are crucial because prognosis, workup and treatment are different in each.     

Cervical paraganglioma with intranuclear vacuoles in a fine needle aspirate

In a 56-year-old man who presented with a cervical mass, a fine needle aspiration specimen was suggestive of a papillary thyroid adenocarcinoma because of the presence of prominent intranuclear vacuoles in rare cells. Operation and subsequent examination of the mass removed from the bifurcation of the carotid artery clearly identified a paraganglioma. This case emphasizes the following points: aspirates of cervical paragangliomas are difficult to interpret, especially when scanty; intranuclear vacuoles are found in cells of a variety of cervical lesions, including paragangliomas, and should not in themselves define the diagnosis of papillary thyroid adenocarcinoma; and aspiration of cervical paragangliomas is probably contraindicated (but may be done unwittingly from time to time).     

Occult medullary carcinoma of thyroid with lymph node metastases: a case report

BACKGROUND: Occult thyroid malignancies presenting with secondary neck masses as the first clinical manifestation is well known. Although rare, medullary carcinoma serves a potential source for lymph node metastases. The characteristic cytomorphology of medullary thyroid carcinoma (MTC) should clinch the diagnosis. Further, fine needle aspiration cytology (FNAC) of the ultrasonography-detected occult nodules in thyroid serves as a useful preoperative diagnostic tool. CASE: A 22-year-old man presented with left-sided neck masses of 1 year duration. FNAC smears of the neck masses revealed cytomorphology characteristic of MTC. Ultrasonography of the thyroid led to ruling out the presence of an occult nodule and detected an 8-mm nodule in the left thyroid lobe. Ultrasound-guided FNAC of the nodule showed features similar to those with FNAC of the neck masses. Surgical resection of thyroid and neck masses further confirmed the diagnosis of a primary occult MTC with lymph node metastases. CONCLUSION: FNAC smears of lymph node masses showing the distinct cytomorphology of MTC should prompt suspicion for occult primary in thyroid. Ultrasound-guided FNAC of these occult nodules, if detected, further serves a diagnostic tool for accurate preoperative diagnosis when metastasis presents as the first clinical manifestation of an occult primary.     

Hepatic metastases from the spindle cell variant of medullary thyroid carcinoma: report of a case with diagnosis by fine needle aspiration biopsy.

BACKGROUND: The liver is a common site of neuroendocrine tumors (NTs) metastatic from primaries in the gastrointestinal tract, pancreas, biliary system and lungs. Medullary thyroid carcinoma (MTC) is also a potential source of metastases of NTs. Their metastases to the liver are frequent and can appear several years after the primitive tumor. Although a wide variety of cytomorphologic features are normally exhibited by MTC in smears, a spindle-shaped cell pattern can predominate, complicating the correct interpretation of a metastasis. CASE: A 63-year-old man presented with multiple liver nodules two years after a total thyroidectomy for MTC. Fine needle aspiration biopsy smears of the liver revealed neoplastic cells occurring in loose groupings or lying singly, most of them with a spindle shape and elongated nucleus with the characteristic "salt and pepper" chromatin pattern of a neuroendocrine tumor. Cytoplasmic dendritic processes and intranuclear inclusions were frequently seen. The cytomorphologic features of the tumor were essentially the same as those of the primary MTC. Immunoreactivity for calcitonin confirmed the diagnosis. CONCLUSION: In fine needle aspiration biopsy of liver masses, knowledge of the spindle pattern of the NT is important in order to achieve a correct diagnosis when metastases are the first manifestation of an occult primary tumor. Among neuroendocrine tumors, MTC must be included in the differential diagnosis.     

Unusual Initial Manifestation of Metastatic Follicular Carcinoma of the Thyroid with Thyrotoxicosis Diagnosed by Technetium Tc 99m Pertechnetate Scan: Case Report and Review of Literature

ObjectiveTo report a case of metastatic thyroid cancer diagnosed on a technetium Tc 99m pertechnetate (TcO₄^–) thyroid scan.MethodsWe present the clinical findings, laboratory results, imaging studies, and surgical pathology report in a man with thyrotoxicosis in whom metastatic well-differentiated thyroid cancer was diagnosed incidentally on a routine TcO₄ ^– thyroid scan in the setting of a presumed diagnosis of benign toxic thyroid disease. In addition, we review the literature regarding coexistence of metastatic thyroid cancer and thyrotoxicosis.ResultsA 68-year-old man with thyrotoxicosis was referred for radioiodine therapy. A routine TcO₄^- thyroid scan revealed high-grade extrathyroidal uptake in the right upper hemithorax as well as in the left side of the thorax. In view of this finding, radioiodine treatment was deferred; further imaging with computed tomography revealed a 6.5-cm mass in a rib on the right side. A biopsy of the rib confirmed the presence of metastatic follicular carcinoma of the thyroid. Scintigraphy revealed sites of metastatic involvement predominantly in the bones along with a cold nodule in the left thyroid lobe, consistent with the primary tumor.ConclusionThis case emphasizes the impact of scintigraphic findings on determining the correct management of a patient who would have otherwise undergone inappropriate treatment. Through an extensive literature review, the incidence of malignant involvement in hyperfunctioning thyroid glands and the possible role of sodium iodide symporter expression by thyroid cancer metastatic lesions in preoperative detection of metastatic sites are addressed. (Endocr Pract. 2009;15:458-462)     

Pancreatic metastasis of cardiac rhabdomyosarcoma diagnosed by fine needle aspiration. A case report.

BACKGROUND: Fine needle aspiration (FNA) is a valuable technique in the diagnosis of soft tissue tumors or their metastases. CASE REPORT: A rhabdomyosarcoma of the left atrium with metastasis to the pancreas was diagnosed by FNA in a 74-year-old female. The patient presented with dyspnea, weight loss and generalized weakness and was found to have a cardiac arrhythmia. Magnetic resonance imaging showed a 9-cm mass in the left atrium and anterior mediastinum. Computed tomography (CT) of the abdomen revealed a 2.8-cm nodule within the head of the pancreas. The patient underwent CT-guided percutaneous aspiration biopsy of the pancreatic mass on the first hospital day and, on the second day, transvenous FNA biopsy of the intracardiac mass. The cytologic morphology and immunocytochemistry of the aspirated material from both sites established a diagnosis of cardiac rhabdomysarcoma with metastasis to the pancreas. CONCLUSION: This is the fifth reported case of rhabdomysarcoma metastatic to the pancreas and the first in which the diagnosis was made by FNA, thereby eliminating the need for open biopsy.     

Fine needle aspiration biopsy of mixed medullary-follicular thyroid carcinoma. A report of two cases

BACKGROUND: Mixed differentiated thyroid carcinomas are rare tumors, difficult to recognize on fine needle aspiration biopsy (FNAB). Most cases are diagnosed only after histologic investigation. CASES: The cases entailed two cytologic samples and a thyroidectomy specimen. Two FNAB thyroidectomy specimens from a 60-year-old man presenting with a solitary thyroid nodule (case 1) were investigated. Both cytologic samples were referred as atypical, with a mixture of features indicating a proliferating follicular lesion but also containing some characteristics of medullary carcinoma. The serum calcitonin level was borderline. Surgery was recommended because of a suspicion of malignancy. The diagnosis of mixed medullary follicular carcinoma was established after a complex histologic investigation. The tumor was encapsulated, with partly microfollicular architecture. Immunohistochemistry was positive for both calcitonin and thyreoglobulin. Electron microscopy from the formol-paraffin block found neurosecretory granules in many cells. The patient was well one year after the operation. One FNAB and thyroidectomy specimen from a 47-year-old woman with long-treated lymphoplasmocellular thyroiditis (case 2) was investigated. The tumor in case 2 was diagnosed on FNAB as medullary carcinoma. Only after histologic and immunohistochemical investigation was mixed differentiation proven. CONCLUSION: Mixed differentiated thyroid tumors are a diagnostic challenge on fine needle aspiration. Irrespective of their rarity, they can be suspected if combined features are present. FNAB recognition of the medullary component in both cases was of crucial importance. Nevertheless, definitive diagnosis remains a histologic problem due to the necessity for topographic information.     

Tibial adamantinoma with local recurrence and pulmonary metastasis: report of a case with histocytologic findings

BACKGROUND: Adamantinoma is a rare primary bone neoplasm of low malignant potential that may recur or metastasize in a mall percentage of patients. The myriad histologic patterns may cause difficulty in distinguishing this tumor from other primary or metastatic neoplasms. The cytomorphologic findings of fine needle aspiration biopsy were reported previously in only a small number of cases. CASE: A 32-year-old man presented with a mass in the distal side of the left leg that was diagnosed as classic adamantinoma by open biopsy. Local recurrence and pulmonary metastases were confirmed by fine needle aspiration biopsy, which showed low grade, uniform cells with nuclear membrane grooves. The patient underwent a below-the-knee amputation and is receiving palliative treatment for progressive pulmonary spread. CONCLUSION: The diagnosis of adamantinoma requires knowledge of compatible clinical and radiologic studies as well as understanding of the variable histologic patterns that one may encounter. Fine needle aspiration biopsy is particularly useful in the diagnosis of recurrent and metastatic adamantinoma. This case report describes a distinctive cytomorphologic feature of nuclear grooves that may be a useful aid in distinguishing the tumor cells of adamantinoma from other cell types.     

Fine needle aspiration of follicular variant of papillary thyroid carcinoma presenting with pleural effusion: a case report

BACKGROUND: Malignant pleural effusion in association with mesothelioma, bronchogenic carcinoma and breast carcinoma is common, although less frequently reported with other malignancies. We report a follicular variant of papillary thyroid carcinoma (FVPTC), diagnosed on fine needle aspiration cytology (FNAC) of thyroid and lymph nodes and subsequently proved to have metastasized to the pleural cavity. CASE: A 46-year-old man presented with history of breathlessness, thyroid swelling, pleural effusion and bilateral cervical lymphadenopathy. FNAC of the thyroid swelling and the lymph nodes showed features of FVPTC with cervical lymph node metastasis. Pleural fluid examination led to suspicion of pleural involvement by metastatic deposit, confirmed by subsequent pleural biopsy. CONCLUSION: Thyroid malignancies presenting with pleural effusion are rare. In this case, although pleural fluid cytology suggested involvement of pleura, a definitive diagnosis could be rendered only on pleural biopsy. An ancillary aid, such as immunocytochemistry, could have helped establish pleural involvement on routine pleural fluid cytology alone. This case emphasizes the possible existence of rare cases of FVPTC that may be associated with a dismal prognosis. In our case, initial diagnosis of FVPTC could be made only on correlating FNA features of thyroid aspirate with those of lymph node aspirate.     

Malignant phyllodes tumor of the breast metastatic to the parotid gland diagnosed by fine needle aspiration biopsy. A case report

BACKGROUND: Phyllodes tumor (cystosarcoma phyllodes) is a rare fibroepithelial neoplasm of the breast. Malignant phyllodes tumor is characterized by an infiltrative border and marked degree of hypercellular stromal overgrowth with > 5 mitoses per 10 high-power fields. Distant metastasis occurs in 10-20% of patients with malignant phyllodes tumor. The most common sites of distant metastases are the lungs, bone and abdominal viscera. Although theoretically any organ may have metastasis, the parotid gland has not been documented before in the English-language literature. CASE: A 40-year-old, Caucasian woman with a history of malignant phyllodes tumor of the left breast presented with a mass on the right side of the parotid gland. Fine needle aspiration biopsy of the mass revealed abundant discohesive spindle cells showing moderate nuclear pleomorphism with occasional mitoses. No epithelial elements were seen. A diagnosis of malignant spindle cell tumor consistent with metastatic malignant phyllodes tumor was made. Histology confirmed the cytologic diagnosis. CONCLUSION: Fine needle aspiration biopsy is accurate and efficient in conjunction with clinical information in the diagnosis of malignant phyllodes tumor of the breast metastatic to the parotid gland.     

Fine needle aspiration of poorly differentiated oxyphilic (Hürthle cell) thyroid carcinoma: a case report

BACKGROUND: Poorly differentiated oxyphilic (Hürthle cell) carcinomas are a more recently described variant of poorly differentiated thyroid carcinoma and are characterized by a prominent Hürthle cell component in a solid or trabecular arrangement. Clinically, poorly differentiated oxyphilic carcinomas behave more aggressively as compared to classic Hürthle cell carcinomas, which have a predominantly follicular pattern. Although the histology of these rare thyroid tumors has been reported in the literature, the cytologic features on fine needle aspiration biopsy have not been described before. CASE: A 73-year-old man with a long history of radioactive iodine and levothyroxine therapy for multinodular goiter presented with a painful, rapidly expanding, 6-cm, left thyroid mass with aggressive radiologic features. Fine needle aspiration biopsy of the mass yielded extremely cellular smears with a dual population of medium-sized follicular cells and numerous Hürthle cells. Subsequent thyroidectomy confirmed the malignant nature of this Hürthle cell-rich tumor, warranting a diagnosis of poorly differentiated oxyphilic (Hürthle cell) thyroid carcinoma. CONCULSION: Poorly differentiated oxyphilic thyroid carcinoma is an aggressive variant of Hürthle cell carcinomas and must enter the differential diagnosis when fine needle aspiration biopsy of a radiologically aggressive thyroid mass yields extremely hypercellular smears with a prominent Hürthle cell component.     

Lifestyle and clinical factors associated with elevated C-reactive protein among newly diagnosed Type 2 diabetes mellitus patients: a cross-sectional study from the nationwide DD2 cohort

The involvement of the testis by metastatic medullary thyroid carcinoma has never been described before. We describe the first case of metastatic medullary thyroid carcinoma affecting testis and inguinal lymph nodes. A 73-year-old Caucasian man was referred to undergo urologic surgery due to a painless nodule in the right testis and an homolateral inguinal lymphoadenomegaly. The patient had a history of medullary thyroid carcinoma with relapsing disease to the spine and lung nodules. Serum calcitonin and CEA levels were 175 pg/ml and 22 ng/ml, respectively. With suspected testicular cancer, the patient underwent radical right orchiectomy with the excision biopsy of the right inguinal lymph node. Histopathology and immunohistochemistry revealed that both the lesions were due to metastases from medullary thyroid carcinoma. Metastases to the testis and inguinal lymph nodes may be due to various solid and hematological tumors. This case, despite its rarity, suggests that testis and inguinal lymph nodes should be considered as potential secondary sites of medullary thyroid carcinoma as well.     

Use of immunohistochemistry in fine needle aspiration of thyroid nodules in patients with a history of malignancy. A report of two cases

BACKGROUND: A history of a nonthyroid malignancy may present a diagnostic dilemma in the assessment of fine needle aspiration (FNA) of thyroid nodules. One reported series, on patients with prior malignancies and a thyroid nodule, indicated that in 17% of patients, the thyroid nodule represented metastatic malignancy, 6% were classified as primary thyroid cancers, and the remainder were benign or inconclusive lesions. The resolution of this problem is essential to patient management. CASES: We report two cases in which patients with a history of renal cell carcinoma presented with a thyroid nodule. The first patient was an 80-year-old female whose Papanicolaou-stained FNA demonstrated clusters of round to polygonal cells with round to ovoid, hyperchromatic nuclei and abundant, wispy cytoplasm. The second patient was a 55-year-old female with clusters and single cells with round to oval, eccentric nuclei and copious, granular, gray cytoplasm noted on Papanicolaou-stained material. In each case, the diagnosis was inconclusive on initial review of Papanicolaou-stained slides, and immunohistochemical staining was ordered to better characterize the lesions. Tumor cells from case 1 were positive for cytokeratin cocktail and vimentin and negative for thyroglobulin, epithelial membrane antigen and calcitonin, suggestive of metastatic renal cell carcinoma. In contrast, the tumor cells from case 2 expressed cytokeratin, thyroglobulin and vimentin, consistent with a primary thyroid neoplasm. In each case, the cytologic diagnoses were confirmed in the resected specimens. CONCLUSION: Immunohistochemistry is a helpful adjunct in the evaluation of thyroid nodules in patients with a past history of malignancy.     

Primary squamous cell carcinoma of the thyroid diagnosed by fine needle aspiration cytology. A report of two cases.

BACKGROUND: Primary squamous cell carcinoma of the thyroid is a rare malignant tumor that needs to be distinguished from other neoplasms. CASES: Two males aged 65 and 68 years presented with an enlarged right lobe of the thyroid. Thyroid scintigraphy revealed a cold nodule. Clinically malignancy was suspected. Fine needle aspiration (FNA) revealed numerous clusters and isolated malignant cells, dyskeratotic cells and deposits of eosinophilic granular keratin material. Subtotal thyroidectomy was performed. Histologic findings confirmed the cytologic diagnosis of squamous cell carcinoma. CONCLUSION: Primary squamous cell carcinoma of the thyroid is a rare tumor. FNA findings of this tumor were not reported before. FNA study cannot help to differentiate primary from metastatic squamous cell carcinoma of the thyroid.     

Diagnosis of cervical thymoma by fine needle aspiration biopsy with flow cytometry. A case report

BACKGROUND: Cervical thymoma is a rare entity. To our knowledge, this is the 20th reported case of cervical thymoma and the fourth case of fine needle aspiration biopsy (FNAB) of this entity. To our knowledge, this is the only case in which cervical thymoma was a diagnostic consideration at the time of the FNAB diagnosis. The diagnosis was rendered because, unlike in previous cases, flow cytometric immunophenotyping was performed. CASE: A 46-year-old, white female presented with what was clinically thought to be a left thyroid nodule. The patient underwent FNAB at an outside institution, and the diagnosis of "possible mixed lymphoma" was made by morphology alone. The patient was referred to our institution for repeat FNAB. Based upon the cytologic findings (cells with lymphoid morphology), flow cytometry was performed, and a diagnosis of cervical thymoma (versus ectopic thymic tissue) was based upon flow cytometry findings combined with morphology. CONCLUSION: When FNAB of a cervical mass, particularly one clinically thought to be a thyroid nodule, shows lymphoid cells without thyroid follicular cells, immunophenotyping may be extremely helpful in arriving at the correct diagnosis.     

Tall cell variant of papillary carcinoma coexisting with chronic lymphocytic thyroiditis. A case report.

BACKGROUND: Recent studies have shown a correlation between lymphocytic thyroiditis and papillary carcinoma of the thyroid. It is thought that autoimmune thyroiditis could be a risk factor for the development of thyroid carcinoma, mainly for the papillary variant. CASE: A 59-year-old female presented with a history of enlargement in the neck and five months of dysphagia. Clinical examination showed generalized expansion and an increase in the hardness of the thyroid gland. Hormonal outline showed subclinical hypothyroidism with serum levels of TSH slightly elevated (5 micrograms/dL; range, 0.25-4). Thyroglobulin antibodies and thyroperoxidase titers were moderately positive. Given these results, a diagnosis of chronic thyroiditis was made. Thyroid ultrasound scan showed diffuse gland irregularity and the presence of a solitary nodule (2.3 cm in diameter) localized in the right lobe. Fine needle aspiration biopsy (FNAB) of the nodule was performed under ultrasound guidance. CONCLUSION: Although clinical and laboratory results supported the diagnosis of autoimmune thyroiditis only, FNAB of the nodular lesion provided evidence of a rare case of papillary carcinoma, tall cell variant, confirmed by histologic results.     

Cytologic diagnosis of alveolar soft part sarcoma of the lower extremity by fine needle aspiration and correlation with core biopsy: a case report

BACKGROUND: Alveolar soft part sarcoma is a rare soft tissue tumor of uncertain origin that is generally slow growing but unmistakably malignant due to its propensity for metastasis to lung, bone and brain early in the course of disease. Fine needle aspiration biopsy (FNAB) of these tumors and recognition of the characteristic cytologic features precludes more invasive diagnostic measures and facilitates appropriate treatment. CASE: A 54-year-old African-American man presented to our institution with a 2-week history of left leg pain. Imaging studies revealed a left leg soft tissue mass just below the popliteal fossa and multiple bilateral lung lesions suggestive of metastatic neoplasm. FNAB of the left lower extremity mass yielded uniform clusters of cells and sigle cells with large nuclei and single prominent nucleoli. Histologically, the biopsy showed nests of large polygonal cells with abundant eosinophilic cytoplasm, round regular nuclei and prominent nucleoli. A periodic acid-Schiff (PAS) stain highlighted intracytoplasmic rhomboidal crystals, a feature diagnostic of alveolar soft part sarcoma. CONCLUSION: Alveolar soft part sarcoma may be diagnosed by its unique morphologic characteristics and should be considered in the differential diagnosis of all cytologically sampled soft tissue lesions.     

Synovial sarcoma of the thyroid. Report of a case with aspiration cytology findings and gene analysis

BACKGROUND: Synovial sarcoma, generally known as a soft tissue tumor, can also occur in the head and neck region, including the thyroid gland. Cytologic findings are important to differentiate the tumor from other types of neoplasms arising in the thyroid gland. CASE: A 60-year-old man complained of hoarseness. A palpable neck tumor was detected, and a computed tomography scan showed a thyroid tumor accompanied by destruction of the thyroid and cricoid cartilage. The results of a preoperative fine needle aspiration biopsy showed numerous spindle cells with pale cytoplasm and oval nuclei with fine, granular chromatin, all of which suggested a medullary carcinoma. The extirpated thyroid tissue weighed approximately 120 g, and a grayish white, elastic, solid tumor (6.8 x 6.5 cm) was present in the left lobe. Histologically, fasciculation of spindle cells that had proliferated solidly and densely was observed. Also, the expression of a chimera gene, SYT-SSX, was detected in the tumor tissue. CONCLUSION: Synovial sarcoma of the thyroid is extremely rare, and its diagnosis by fine needle aspiration biopsy is generally considered very difficult. The detailed cytologic findings observed here might be helpful with the differential diagnosis of thyroid neoplasms.