Intrathyroidal epithelial thymoma (ITET)/carcinoma showing thymus-like differentiation (CASTLE) exhibits CD5 immunoreactivity: new evidence for thymic differentiation

Intrathyroid thymic carcinoma: A clinicopathological analysis of 22 cases

OBJECTIVE

Intrathyroid thymic carcinoma (ITTC) is a rare malignancy. The current understanding of ITTC is inadequate, and there is no standard treatment for ITTC. In the present study, we aimed to explore the clinicopathological characteristics of ITTC and identify potential therapeutic targets.

METHODS

The clinicopathological characteristics of 22 ITTC patients at our institution were reviewed. The expression of DNA mismatch repair (MMR) proteins and PD-L1 in ITTC were assessed by immunohistochemistry (IHC).

RESULTS

All patients underwent surgery. There were nine females and 13 males, with a slight male predominance. Their ages ranged from 42 to 79 years (average, 54. 1 years). The diameters of the neck masses ranged from 10 to 100 mm (average, 39 mm). Ipsilateral lymph node (LN) dissection was performed in 18 patients: 12 demonstrated LN metastasis, six showed no LN metastasis, and no lymph nodes were dissected in four. One patient had liver metastasis. CK5/6, P63, CD5, and CD117 were expressed in all cases. All cases were negative for TTF1, PAX8, thyroglobulin, and BRAF V600E. DNA MMR protein expression was retained in all tested tumors, and EBV-encoded small RNA (EBER) in situ hybridization was consistently negative. The Ki67 proliferation index ranged from 10 to 70 %. All patients were followed-up for 14-134 months, four died, six were lost to follow-up, and the remaining patients survived without disease. The PD-L1 combined positive score ranged from 10 to 80 (average: 40).

CONCLUSION

Our results confirm that CD5 and CD117 co-expression support a diagnosis of ITTC. All tumors in this cohort were DNA MMR-proficient and were not associated with Epstein-Barr virus (EBV) infection. A high CPS for PD-L1 suggests that immune checkpoint inhibitor therapy may be worthy of further exploration in patients with ITTC.

Case report and literature review: thyroid carcinoma showing intrathyroid thymic carcinoma

Background

Intrathyroid thymic carcinoma (ITTC) is a rare malignancy of the thyroid gland with histological and immunophenotypic resemblance to thymic carcinoma. Surgery combined with adjuvant radiotherapy improves the survival of patients with ITTC. However, for patients with extensive metastases, there is currently no effective treatment. Chemotherapy is an option but has not demonstrated improved patient survival.

Methods and results

A female patient presented with metastases to the pleura, lung, and bone 16 years after surgery for ITTC. As radiotherapy and chemotherapy failed to control the recurrent disease, lenvatinib treatment was initiated. After 3 months, positron emission tomography/computed tomography showed a substantial reduction of all metastatic lesions and decreased tumor metabolism. The patient continues to receive lenvatinib and remains well and symptom-free.

Conclusion

For patients with ITTC who have progressive, life-threatening metastases, lenvatinib represents a valuable salvage therapy that may offer a sustained reduction in tumor burden and maintenance of quality of life.

Carcinoma showing thymus-like differentiation (CASTLE) of the salivary gland: Report of 2 cases of a hitherto under-recognized extrathyroid counterpart

Carcinoma showing thymus-like differentiation (CASTLE) outside the thyroid gland is extremely rare. Here we report two cases of CASTLE of the major salivary gland. The tumors occurred in the parotid gland of a 31-year-old female (Case 1) and in the submandibular gland of a 40-year-old female (Case 2). Both tumors showed a lobulated growth pattern, and were histologically composed of a nested or sheet-like proliferation of carcinoma cells with round- to oval-shaped nuclei, distinct nucleoli and pale eosinophilic cytoplasm, accompanied by various degrees of lymphocytic infiltration. Immunohistochemical staining revealed that the tumors were positive for pan-cytokeratin, p40, CD5, CD117 and bcl-2. In addition, PD-L1 expression was seen in 10-90% of tumor cells. After the initial surgery, Case 1 remained tumor-free for 20 months, while Case 2 suffered lymph node recurrence at 4 months, followed by lung metastasis, which was treated with chemoradiotherapy and anti-PD-1 immune checkpoint inhibitor, resulting in a partial response. The present findings indicate that an extrathyroid counterpart of CASTLE can occur as a primary salivary gland neoplasm. Salivary CASTLEs seem to show a wide range of biological behavior, and long-term follow-up may be needed. Immune checkpoint inhibitor targeting PD-1 might become a promising treatment option in patients with CASTLE; however, further study with a larger number of cases is necessary to establish the optimal therapeutic strategy and prognostic factors for this rare cancer.

Identification of Recurrent TERT Promoter Mutations in Intrathyroid Thymic Carcinomas

Intrathyroid thymic carcinoma (ITTC) is a rare malignant neoplasm considered to be a eutopic thymic carcinoma (TC) arising ectopically in the thyroid. Histopathologically, ITTC resembles squamous cell carcinoma of the thymus with positive TC markers such as CD5 and c-KIT. Despite these similar histological findings, ITTC is clinically less aggressive than TC. In this study, we compared clinical, histological, and genetic characteristics of ITTCs and TCs. We collected 9 ITTCs and 8 TCs with their clinicopathological profiles. Immunohistochemistry for CD5, p63, CD117/c-KIT, Ki-67, p53, TTF-1, thyroglobulin, PAX8, EGFR, and PD-L1/CD274 plus in situ hybridization for EBER was performed. We further investigated mutation status of KIT, EGFR, BRAF, and TERT promoter using Sanger sequencing. In our study, ITTCs affected significantly younger patients than TCs. After a mean follow-up of 86 months, all patients with ITTC were alive, while two patients with TC had died. Immunohistochemistry showed ITTCs and TCs had a similar immunophenotype except for EGFR and p53. Genetic analysis did not identify KIT or BRAF mutations in any ITTCs or TCs. EGFR mutations were positive in 11% (1/9) of ITTCs and 25% (2/8) of TCs. Notably, TERT promoter C228T mutation was identified in 22% (2/9) of ITTCs but none of the TCs. There were no significant differences in age, tumor size, or sex between TERT-mutated and TERT-wild-type ITTCs. Collectively, ITTC and TC have similar histopathologic and immunophenotypic features but different clinical outcomes. Recurrent TERT promoter mutation may be a key event related to cancer progression in ITTCs and warrants further investigation.

Carcinoma Showing Thymus-Like Differentiation (CASTLE) Arising in the Sublingual Gland

Carcinoma showing thymic-like differentiation (CASTLE) is a rare tumor most commonly occurring in the thyroid and soft tissues of the neck. We report the first case of CASTLE occurring in the sublingual gland. The patient, a 35-year-old healthy man, presented with a submucosal lesion located in the anterior right floor of the oral cavity and an ipsilateral neck mass. The lesion had been previously investigated by neck computed tomography and ultrasound-guided fine needle aspiration cytology and diagnosed as metastatic squamous cell carcinoma. After oral cavity magnetic resonance imaging, positron emission tomography, and a non-diriment, fine needle aspiration cytology of the sublingual mass, the patient was treated as affected by a sublingual gland malignancy with removal of primary tumor and neck dissection. Morphological and immunohistochemical findings were diagnostic for primary sublingual gland CASTLE. The patient received adjuvant radiotherapy and is free of disease 2 years after treatment. We describe the pathological features of the lesion and discuss the possible differential diagnoses.

Soft Tissue Special Issue: Adamantinoma-Like Ewing Sarcoma of the Head and Neck: A Practical Review of a Challenging Emerging Entity

Adamantinoma-like Ewing sarcoma (ALES) is a rare variant of Ewing sarcoma that is defined by complex epithelial differentiation, including expression of cytokeratin and p40 and frequent keratin pearl formation. In recent years, ALES has been increasingly recognized in the head and neck, where it can mimic a wide range of small round blue cell tumors and basaloid carcinomas. However, there has been persistent controversy regarding whether ALES is best classified and managed as a sarcoma or carcinoma. This review summarizes the characteristic clinical, pathologic, immunophenotypic, and molecular features of ALES with an emphasis on differential diagnosis and tumor classification.

Thyroid Carcinoma Showing Thymus-Like Differentiation (CASTLE) with Tracheal Invasion: A Case Report

Patient: Male, 49-year-old

Final Diagnosis: Thyroid carcinoma showing thymus-like differentiation (CASTLE)

Symptoms: Hoarseness

Medication: —

Clinical Procedure: Thyroidectomy

Specialty: Surgery

Intrathyroidal thymic carcinoma exhibiting neuroendocrine differentiation: Case report with cytomorphology, immunocytochemistry, and review of the literature focusing on cytology

Intrathyroidal thymic carcinoma is a malignant epithelial tumor of the thyroid gland with thymic epithelial differentiation; it is the malignant counterpart of ectopic thymoma of the thyroid gland and histologically resembles thymic carcinoma. Given its favorable prognostic course, preoperative cytological diagnosis is important to distinguish this neoplasm from other more aggressive thyroid neoplasms that can have similar or overlapping cytomorphological features. However, there is little information about the cytology of this disease available in the literature, even in the latest fourth edition of World Health Organization classification of tumors of endocrine organs. Here, we report a case of intrathyroidal thymic carcinoma exhibiting neuroendocrine differentiation in a 33-year-old woman and present a review of the literature.

The 'CASTLE' tumour: An extremely rare presentation of a thyroid malignancy. A case report

Thyroid carcinoma showing thymic-like differentiation (CASTLE) is a rare malignancy of the thyroid gland, and it accounts for 0.1–0.15% of all thyroid cancers. As the name suggests, it has a histological and immunophenotypic resemblance to thymic carcinoma. Preoperative diagnosis of CASTLE can be difficult as its clinical manifestations, and histological characteristic resembles other aggressive and advanced thyroid carcinomas. It is essential to distinguish CASTLE from other aggressive neoplasms as the former has a more favourable prognosis. Immunohistochemical staining with CD5 can help to differentiate thyroid CASTLE from other aggressive thyroid neoplasms.

Due to the rarity of this disease, there is no clear definitive treatment strategy. Surgical resection of CASTLE is usually attempted initially. Nodal involvement and extrathyroidal extension are shown to be the main prognostic factors that influenced the survival of patients. Therefore, complete resection of the tumour is vital to reduce local recurrence rates and to improve the chance of long-term survival. Radiotherapy (RT) for CASTLE is an effective treatment. Curative surgery followed by adjuvant RT should be considered in cases with extrathyroidal extension and nodal metastases. With RT, shrinkage of the tumour and reduction of local recurrence rate is possible.

With that in mind, we present a case of CASTLE who presented with airway compression symptoms three years after thyroid surgery. He subsequently underwent tumour debulking surgery and a tracheostomy. The patient refused adjuvant chemoradiotherapy, and during our serial follow-up, he is well and symptom-free.

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Thyroid carcinoma showing thymic-like differentiation (CASTLE) is a rare malignancy of the thyroid gland.

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Diagnosis of CASTLE can be difficult as it resembles other aggressive and advanced thyroid carcinomas.

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Immunohistochemical staining with CD5 can help to differentiate thyroid CASTLE from other aggressive thyroid neoplasms.

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Complete surgical resection is vital to reduce local recurrence rates and to improve the chance of long-term survival.

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Adjuvant radiotherapy should be considered in cases with extrathyroidal extension and nodal metastases.

Clinical outcome of intensity modulated radiotherapy for carcinoma showing thymus-like differentiation

PURPOSE

To evaluate the efficacy and toxicity of adjuvant intensity-modulated radiotherapy (IMRT) after surgery for carcinoma showing thymus-like differentiation (CASTLE).

METHODS

Between September 2008 and June 2015, 14 CASTLE patients were retrospectively enrolled. The clinical features, treatment procedure and clinical outcomes were reviewed. All patients received postoperative IMRT. The radiation doses ranged from 56Gy/28 fractions to 66Gy/33 fractions. Treatment-related toxicities were graded by National Cancer Institute Common Toxicity Criteria (NCI-CTC) version 3.0.

RESULTS

After a median follow-up period of 42 months, only one patient suffered local recurrence and distant metastasis. The most frequently seen acute toxicities were mucositis and dermatitis (grade 1-2). No grade 3-4 toxicities were observed.

CONCLUSIONS

Although based upon a small series of consecutively treated patients, our study showed that adjuvant IMRT provides satisfactory local-regional control for CASTLE, with acceptable toxicities. Further studies are still warranted to clarify our findings.

CASTLE Thyroid Tumor: A Case Report and Literature Review

Carcinoma showing thymus-like differentiation is a rare tumor of the thyroid gland, which is structurally similar to thymic tissue. Overall, it has a favorable prognosis. Radiotherapy has been shown to be an effective local treatment, but there have been reports of distant recurrence. It has been suggested that adding chemotherapy may decrease the risk of recurrence. Here, we present a case report of a patient with a large tumor and extrathyroidal extension. The patient was treated with surgery, radiotherapy, and cisplatin with acceptable toxicity. The patient is free of locally recurrent or distant disease at 3 years.

Carcinoma Showing Thymus-Like Differentiation (CASTLE): Cytopathological Features and Differential Diagnosis

BACKGROUND

CASTLE (carcinoma showing thymus-like differentiation) is a rare tumor (accounting for less than 0.15% of thyroid neoplasms) with most of the reported cases from Asia. Although this tumor is rare, distinguishing it from more aggressive neoplasms is critical because of its improved prognosis. To date, there have been limited studies on its cytomorphological features. Herein, we review the cytomorphological features of 10 fine-needle aspiration (FNA) cases of histologically confirmed CASTLE and discuss the findings in light of the current literature.

METHODS

We retrospectively (1989-2016) identified 10 cases of CASTLE from 17,415 surgical cases of thyroid carcinoma from The Johns Hopkins Hospital and Fudan University Shanghai Cancer Center. The cases were reviewed for discrete cytomorphological characteristics.

RESULTS

All of the cases displayed predominantly single (dishesive) epithelial cell populations, high nuclear/cytoplasmic ratios, hyperchromatic to open/vesicular nuclei and macronucleoli. The majority of cases additionally showed hypercellular, three-dimensional fragments in a background of lymphocytes. The fragments displayed syncytial architecture without molding and rarely squamous differentiation. All cases lacked follicular differentiation, intranuclear inclusions, nuclear molding, or neuroendocrine-type chromatin.

CONCLUSIONS

Cytopathological features alone do not appear to be distinctive or definitive of CASTLE but rather allow for the inclusion of CASTLE within the differential diagnosis. Procurement of cell block material is important and resulted in the single case of CASTLE accurately diagnosed on FNA. Cytopathological features that favored CASTLE included syncytial fragments of malignant cells with pleomorphic large nuclei, vesicular chromatin, and prominent nucleoli in a background of lymphocytes. These cytopathological findings in the appropriate clinicoradiological context warrant its inclusion in the reported differential diagnosis in order to be able to implement appropriate clinical management.

Carcinoma of the Neck Showing Thymic-like Elements (CASTLE): Report of a Case and Review of the Literature

Carcinoma showing thymic-like elements (CASTLE) is a rare tumor affecting thyroid and neck soft tissues, which has to be distinguished from squamous cell and anaplastic thyroid carcinoma, because it has a better prognosis. We report a new case of CASTLE which occurred in a patient submitted to total thyroidectomy with central neck dissection. The tumor stained positively for CD5, which seems to be the most useful marker in the differential diagnosis. By the analysis of the 18 cases reported in literature, total thyroidectomy with selective modified neck dissection should be the treatment of choice and radiotherapy should be considered for patients with positive nodal status.

CT and MR imaging of thyroid carcinoma showing thymus-like differentiation (CASTLE): a report of ten cases

OBJECTIVE

To study the CT and MR imaging features of carcinoma showing thymus-like differentiation (CASTLE) and to raise awareness of this rare thyroid tumour.

METHODS

The imaging appearances of 10 CASTLE tumours confirmed by surgical pathology were retrospectively reviewed and correlated with clinical and histological findings.

RESULTS

Seven patients with newly diagnosed and three patients with recurrent tumours were identified (six males and four females). CASTLE tumours were commonly located in the lower neck between the inferior pole of the thyroid and the upper mediastinum. The average tumour size was 4.2 cm (range: 2.5-6 cm). On plain CT scans, most tumours were ill-defined nodular masses of uniform density. After enhancement, most cases showed mild enhancement, while heterogeneous enhancement could be seen in more than half the cases. On the MR images, tumours presented with homogeneous isointensity on T1 weighted images and they appeared to be slightly hyperintense on T2 weighted images. On post-contrast images, marked enhancement was seen in two patients, and heterogeneous enhancement was seen in three cases. Aggressive local infringements mainly included the ipsilateral strap muscle, tracheoesophageal groove area and tracheal wall. The specimens stained positively for CD5 and CD117, indicating thymic differentiation.

CONCLUSION

CASTLE has no characteristic imaging features when compared with other thyroid nodules, except for its unique location in the lower neck between the inferior pole of the thyroid and the upper mediastinum. CD5- and CD117-specific immunoreactivity is useful for diagnosis.

ADVANCES IN KNOWLEDGE

We reported 10 cases of CT and MR images illustrating the features of CASTLE, and we raised the level of awareness of this rare malignant thyroid tumour.

Thyroid Carcinoma Showing Thymic-Like Differentiation Causing Fracture of the Trachea

Thyroid carcinoma showing thymic-like differentiation (CASTLE) comprises a rare neoplasm of the thyroid gland which arises from ectopic thymic tissue or remnants of brachial pouches. CASTLE is regarded as an indolent neoplasm with a favorable prognosis, irrespective of its metastatic potential. Diagnosis is difficult as clinicopathological features have not been yet well-defined. Radiological findings are not specific and only immunohistochemical positivity for CD5 and CD117 staining is highly suggestive of CASTLE. Despite lack of universally accepted treatment recommendations, the mainstay treatment includes thyroidectomy and systematic lymph node dissection. We report a case of CASTLE tumour with very uncommon characteristics developed in a 76-year-old man, who presented with rapidly deteriorating dyspnea and severe cough, resulting in respiratory failure. At surgery, a suspicious looking tumour arising from the upper pole of the right lobe of the thyroid gland, surrounding the trachea and displacing the right common carotid artery, was identified. The patient underwent en bloc resection of the tumour with the thyroid gland and regional lymph node dissection. This is the first reported case of CASTLE causing tracheal ring fracture.

Clinical analysis of 82 cases of carcinoma showing thymus-like differentiation of the thyroid

The aim of the present study was to summarize the clinical characteristics, diagnosis, treatment and prognosis of carcinoma showing thymus-like differentiation of the thyroid (CASTLE). A search of the relevant literature was conducted, which identified 82 cases of CASTLE reported to date. A review of the clinical and auxiliary examination data, treatment, pathological findings and follow-up of these cases was performed. The clinical manifestations of CASTLE varied and did not demonstrate specificity. During ultrasound examination, CASTLE was described as a solid and hypoechoic mass, and the echo was typically observed to be heterogeneous. In computed tomography (CT), CASTLE was demonstrated to be a well-defined, soft tissue density mass without calcification, which appeared enhanced following administration of contrast medium. In emission CT, CASTLE was revealed as a ‘cold nodule’. A total of 78 patients underwent radical surgery, and 12 patients experienced recurrence. Lymph node metastasis did not promote recurrence, and postoperative radiation was not able to reduce the recurrence rate (P=0.144 and 1.000, respectively). The median follow-up time was 14 months (range, 1–312 months). Typical immunohistochemical examinations demonstrated the specimens to be positive for cluster of differentiation (CD)5, CD117, cytokeratin 19, epithelial membrane antigen and tumor protein 63, and negative for calcitonin, thyroglobulin and thyroid transcription factor-1. Thyroid CASTLE is a rare malignancy whose exact diagnosis relies on pathological examination, particularly immunohistochemistry, since preoperative examinations are usually unable to provide an exact diagnosis. Radical resection is the primary treatment for CASTLE, which presents favorable prognosis.

Carcinoma showing thymus-like elements of the thyroid gland: report of three cases including one case with breast cancer history

Carcinoma showing thymus-like elements (CASTLE) is a rare malignant tumor of the thyroid or adjacent neck soft tissues, whose histogenesis is still debated. It may resemble other primary or metastatic poorly differentiated tumors histologically and the differential diagnosis is crucial for CASTLE has a better prognosis. However, CASTLE as a second primary tumor has not been reported in the literature. We report three cases of thyroid CASTLE, including a unique tumor following breast-conserving surgery for early-stage breast invasive carcinoma. There were two female and one male. All three tumors were located in the right lobe of the thyroid, and one tumor showed extension into the surrounding soft tissue. Histologically, all tumors showed expansive growth and consisted of cords, nests or sheets of epithelial cells divided into irregularly shaped lobules by fibrous connective tissue with lymphoplasmacytic infiltration. Focal squamous differentiation resembling Hassall's corpuscles were observed. All cases stained positively for CD5, CD117, high molecular weight cytokeratin, cytokeratin, P63, carcinoembryonic antigen and epithelial membrane antigen. Positive staining for Bcl-2 in two cases and chromogranin A in one case was noted. Ki-67 expression ranged from 15 to 25%. Thyroid transcription factor and CD3 were negative. There was no evidence of recurrent or metastatic disease at following surgery. These features demonstrated CASTLE may arise from branchial pouch remnants, the thyroid solid cell nests. CASTLE is a rare entity, awareness of its occurrence as a second primary tumor is important to avoid overtreatment because it is associated with a favorable prognosis.

Potential Role of Adjuvant Radiation Therapy in Cervical Thymic Neoplasm Involving Thyroid Gland or Neck

PURPOSE

The purpose of this study is to assess the clinicopathologic features, treatment outcomes, and role of adjuvant radiation therapy (RT) in cervical thymic neoplasm involving the thyroid gland or neck.

MATERIALS AND METHODS

The medical and pathologic records of eight patients with cervical thymic neoplasm were reviewed retrospectively. All patients underwent surgical resection, including thyroidectomy or mass excision. Adjuvant RT was added in five patients with adverse clinicopathologic features. The radiation doses ranged from 54 Gy/27 fractions to 66 Gy/30 fractions delivered to the primary tumor bed and pathologically involved regional lymphatics using a 3-dimensional conformal technique.

RESULTS

Eight cases of cervical thymic neoplasm included three patients with carcinoma showing thymus-like differentiation (CASTLE) and five with ectopic cervical thymoma. The histologic subtypes of ectopic cervical thymoma patients were World Health Organization (WHO) type B3 thymoma in one, WHO type B1 thymoma in two, WHO type AB thymoma in one, and metaplastic thymoma in one, respectively. The median age was 57 years (range, 40 to 76 years). Five patients received adjuvant RT: three with CASTLE; one with WHO type B3; and one with WHO type AB with local invasiveness. After a median follow-up period of 49 months (range, 11 to 203 months), no recurrence had been observed, regardless of adjuvant RT.

CONCLUSION

Adjuvant RT after surgical resection might be worthwhile in patients with CASTLE and ectopic cervical thymoma with WHO type B2-C and/or extraparenchymal extension, as similarly indicated for primary thymic epithelial tumors. A longer follow-up period may be needed in order to validate this strategy.

Clinical analysis of thyroid carcinoma showing thymus-like differentiation: report of 8 cases

Thyroid carcinoma showing thymus-like differentiation (CASTLE) is a kind of rare neoplasm of the thyroid gland. Because thyroid CASTLE is rare and difficult to diagnose, its clinicopathologic features have not been well defined, and no universally accepted treatment recommendation is available. We analyzed retrospectively the clinicopathologic data of 8 patients with thyroid CASTLE who underwent surgery and radiotherapy at the Shengjing Hospital of China Medical University between December 2008 and June 2012. All patients accepted radical surgery. All patients accepted postoperative radiotherapy, except one 79-year-old patient. There was no evidence of recurrence or metastasis during the follow-up period. The pattern of immunohistochemical staining was similar to that of thymic carcinoma. Six of 8 CASTLE cases expressed CD5. All 8 CASTLE patients were negatively expressed in thyroglobulin, thyroid transcription factor 1, and calcitonin. Patients with thyroid CASTLE have good outcomes after radical resection and postoperative radiotherapy. Positive CD5 immunoreactivity can contribute to diagnosis of this disease.

Papillary thyroid carcinoma with predominant spindle cell component: report of two rare cases and discussion on the differential diagnosis with other spindled thyroid neoplasm

Spindle cell transformation or metaplasia has been so far demonstrated in the context of both benign and malignant conditions. Spindle cell lesions of the thyroid gland of either primary or secondary origin to metastatic disease represent rare entities. We describe two patients with papillary thyroid carcinoma (PTC) showing spindle cell metaplasia, submitted to thyroidectomy due to euthyroid bilateral nodular thyroid disease. Cytological examination of fine-needle aspiration biopsy performed in the dominant nodules was consistent with follicular neoplasm in one case and with a hyperplastic/adenomatous nodule in the other patient. Histological examination disclosed unencapsulated follicular variant of PTC with spindle cell metaplasia in either cases. Both patients are doing well without clinical or laboratory evidence of PTC recurrence at 3- and 1-year follow-up, respectively. We present the clinical, pathological, and immunohistochemical aspects of these unusual cases and thoroughly discuss the differential diagnosis with other spindle cell lesions of the thyroid gland.

Sonographic findings in three cases of carcinoma showing thymus-like differentiation

Carcinoma showing thymus-like differentiation (CASTLE) is a rare tumor of the thyroid gland or soft tissues of the head and neck. To our knowledge, there have been only a few reports concerning imaging findings of CASTLE. We report herein the sonographic appearances of three cases of CASTLE. Two tumors were located at the lower part of the thyroid and one had spread throughout the thyroid. Sonograms showed heterogeneously solid tumors without cystic components or calcification. The central part of the tumor was slightly hyperechoic compared with the peripheral part of the tumor. Histologically, the tumors were composed of a mixture of fibrous stroma and epithelial nests.

A carcinoma showing thymus-like elements of the thyroid arising in close association with solid cell nests: evidence for a precursor lesion?

BACKGROUND

Carcinoma showing thymus-like elements (CASTLE) is a rare malignant neoplasm of the thyroid gland, morphologically and immunohistologically similar to a thymic carcinoma, whose histogenesis is still debated. Hypotheses include an origin from ectopic thymic tissue, vestige of the thymopharyngeal duct, or branchial pouch remnants from which solid cell nests (SC-nests) originate. The diagnosis of CASTLE may be treacherous due to its rarity and its propensity to mimic other poorly differentiated tumors such as squamous cell carcinoma.

METHODS

We present a case of CASTLE in a 58-year-old man initially diagnosed as a poorly differentiated squamous cell carcinoma both on fine-needle aspiration cytology (FNAC) and on biopsy, arising in close association with SC-nests. A thorough literature review, with special emphasis on its diagnosis and histogenesis of CASTLE, was also conducted.

RESULTS

Magnetic resonance images revealed a 4.0-cm cervical mass on the left side of the trachea, involving the lateral middle/inferior portion of the left lobe of the thyroid gland. FNAC was performed with a diagnosis of "malignant cells, consistent with squamous cell carcinoma." A histological evaluation of the resected specimen revealed a malignant proliferation of cells, focally exhibiting a squamoid appearance, which were immunopositive for CD5 and p63. A diagnosis of CASTLE was made. The tumor was located in direct continuity with SC-Nests, and the cell morphology of both the SC-nests and CASTLE was very similar with merging. Moreover, the immunohistochemical expression profiles of most markers useful in the diagnosis of CASTLE were identical in the SC-nests.

CONCLUSIONS

The inclusion of CASTLE in the differential diagnosis of poorly differentiated tumors of the thyroid region and the use of ancillary studies are essential to diagnose this rare entity associated with a relatively favorable prognosis. The close association of CASTLE with SC-nests opens the way to a new scenario for studies of its histogenesis.

Management of thyroid carcinoma showing thymus-like differentiation (CASTLE) invading the trachea

PURPOSE

To define the clinicopathological features and discuss the optimal management of carcinoma showing thymus-like differentiation (CASTLE).

METHODS

We retrospectively analyzed six patients with CASTLE.

RESULTS

The subjects comprised two men and four women (average age at initial diagnosis, 61 years, range 47-75 years). Preoperative biopsy yielded a correct diagnosis in two patients. Five patients underwent surgery and one was treated with radiation therapy alone. Four had extrathyroidal invasion and three had lymph node metastasis. During the clinical course, tracheal invasion was detected in five patients, the upper extent of the tumor being the lower half of the first tracheal ring. Two of these patients underwent tracheal sleeve resection. Two patients received postoperative radiotherapy for nodal metastasis, and one, after palliative surgery. The median follow-up period was 67 months (range 38-129). Recurrence was found 10 years post-therapy in the patient treated with radiation therapy only, resulting in death soon after. Although local recurrence was not found in the remaining five patients, new pulmonary metastases were diagnosed in the patient who underwent non-curative surgery.

CONCLUSIONS

CASTLE can be diagnosed preoperatively by core needle biopsy and CD5 staining. Curative resection with neck dissection followed by radiotherapy can yield a good outcome. Larynx-sparing complete resection may be more feasible for CASTLE, even though it has a higher incidence of tracheal invasion than differentiated thyroid carcinoma.

Primary pure squamous cell carcinoma of the thyroid: report and histogenic consideration of a case involving a BRAF mutation

Primary squamous cell carcinoma of the thyroid (SCC-T) is extremely rare. Its clinical presentation is similar to that of anaplastic carcinoma. Metastasis or extension from the head and neck area should be ruled out, as patients with SCC-T have a poorer prognosis than patients who have a thyroid extension from an adjacent tumor. An 87-year-old man presented with a longstanding painless mass in the right thyroid and had experienced 2 months of pain upon swallowing. A right lobectomy was performed with resection of thyroid cartilage, cricoid cartilage, a portion of the first to third tracheal ring and the right neck lymph node. A histological examination revealed pure SCC. The tumor cells showed diffuse immunoreactivity to CK5/6, CK19 and p63. Immunoreactivity to EMA and p53 was focally positive. TTF-1, galectin 3 and thyroglobulin immunoreactivity was restricted to the non-neoplastic thyroid tissue. Both tumor cells and non-neoplastic follicular cells were negative for CD5. The MIB-1 index was 36%. DNA extracted from the tumor identified a BRAF V600E mutation in exon 15 and a BRAF G468A mutation in exon 11, whereas DNA from non-tumorous cells did not contain a mutation. These molecular findings may suggest a direct transformation from papillary carcinoma to SCC-T.

Outcome of radical resection and postoperative radiotherapy for thyroid carcinoma showing thymus-like differentiation

BACKGROUND

Carcinoma showing thymus-like differentiation (CASTLE) is a rare disease that is difficult to diagnose. The aim of this study was to assess the effects of combined-modality treatment in CASTLE patients.

METHODS

We retrospectively studied patients identified between January 1, 2000 and December 31, 2009 as having CASTLE and who subsequently underwent surgery and radiotherapy or chemotherapy. Preoperative laboratory findings, ultrasonographic (US) and computed tomographic (CT) features, and fine-needle aspiration biopsy (FNAB) specimens were evaluated.

RESULTS

Seven patients with CASTLE were identified (four men, three women). The median age at initial diagnosis was 48 years (range 25-56 years). The five newly diagnosed patients were treated with curative surgery and postoperative radiotherapy, whereas two patients with recurrent disease were treated with salvage surgery plus radiotherapy or chemotherapy. All patients were disease-free at a median follow-up period of 34 months (range 12-61 months). The pattern of immunohistochemical staining was similar to that of thymic carcinoma. Specimens from all seven patients stained positively for CD5, CD117, and cytokeratin but were uniformly negative for thyroglobulin, thyroid transcription factor 1 (TTF-1), and calcitonin.

CONCLUSIONS

Patients with CASTLE have excellent outcomes after curative resection and postoperative radiotherapy compared with patients with anaplastic thyroid carcinoma. Even patients with local recurrent disease benefited from salvage surgery with subsequent operation and/or radiotherapy. CD5 immunohistochemical staining on FNAB samples may help identify the possible entities that are part of the differential diagnosis.

Cytological findings of intrathyroidal epithelial thymoma/carcinoma showing thymus-like differentiation: a study of eight cases

The purpose of this article is to describe the cytologic findings of intrathyroidal epithelial thymoma/carcinoma showing thymus-like differentiation (ITET/CASTLE) in detail and discuss its differential diagnoses. We examined cytologic specimens taken from eight ITET/CASTLE cases, who underwent fine needle aspiration. Cytologic features of ITET/CASTLE include (1) hypercellularity, (2) large cell clusters without papillary or follicular pattern, (3) round or spindle tumor cells with distinct nucleoli and cell border, (4) few keratinized cells and intracytoplasmic lumina (ICL), and (5) lymphocytic background. The differential diagnoses included poorly differentiated carcinoma, metastatic lymphoepithelioma, squamous cell carcinoma, and mucoepidermoid carcinoma. The presence of individual keratinizing cells and ICL and the location of the tumor may be helpful in indicating ITET/CASTLE.

Thyroid carcinoma showing thymus-like differentiation (CASTLE): case report with cytomorphology and review of the literature

Thyroid carcinoma showing thymus-like differentiation (CASTLE) is a rare tumor of the thyroid gland or adjacent soft tissues of the neck. Given the comparatively good prognosis of CASTLE, it is crucial to distinguish this neoplasm from other more aggressive thyroid neoplasms that can have similar or overlapping cytomorphological features. However, there is little information about the cytomorphology of CASTLE available in the literature. Here we report the cytomorphology and histology of thyroid CASTLE in a 52-year-old woman and present a review of the literature.

Management of carcinoma showing thymus-like element

OBJECTIVE

To consolidate the key features of carcinoma showing thymus-like element, including its management.

METHOD

We present our experience of the difficult diagnosis and management of this rare tumour. We also present the results of an extensive literature search, documenting those aspects of the clinical picture, natural history and management of carcinoma showing thymus-like element which are relevant to head and neck surgeons.

RESULT

Intrathyroidal, epithelial carcinoma showing thymus-like element is a rare, malignant tumour of the thyroid gland, with histopathological features similar to squamous cell carcinoma but a more favourable prognosis. It is usually treated surgically using a combination of total thyroidectomy and selective neck dissection, with radiotherapy and chemotherapy in selected cases.

CONCLUSION

Carcinoma showing thymus-like element of the thyroid gland is a rare condition. Head and neck surgeons with a thyroid interest should be aware of this tumour, because of its close histological resemblance to other, commoner malignancies of the thyroid gland.

CASTLE tumour of the neck: a rare location of a malignant tumour of the thymus

We present the case of a 62-year-old woman who consulted her physician in December 2005, suffering from a mass at the left lower anterior neck with rapid enlargement. Intraoperative frozen section was highly suspicious of a CASTLE tumour (carcinomas showing thymus-like differentiation). Finally, immunohistochemical investigation revealing positivity for CK5/6, c-kit (CD117) and CD5 as well as negativity for thyroglobulin, calcitonin, vimentin and TTF-1 confirmed the diagnosis. Due to lymph node metastases, radiochemotherapy was performed. Fifteen months after the initial diagnosis disseminated pulmonary metastases were found and treated with cisplatin based chemotherapy, which led to a stabilisation of the disease. In June 2008, computed tomography showed progress of the pulmonary metastases, making further chemotherapeutical treatment necessary. Although treatment was changed in October 2008, the staging evaluation in January 2009 revealed further progress of the metastatic disease. Currently, the patient is still alive, but receives no medical treatment at the moment.

Carcinoma showing thymus-like differentiation (CASTLE) of thyroid: a case report and literature review

Carcinoma showing thymus-like differentiation (CASTLE) is a rare malignant neoplasm that occurs in the thyroid gland, or head and neck. This tumor arises from either ectopic thymus tissue or remnants of branchial pouches, which retain the potential to differentiate along the thymus line. Clinical presentation and imaging can be consistent with a malignant lesion such as thyroid cancer or thymic carcinoma. Immunohistochemical staining with CD5 can differentiate CASTLE from other malignant thyroid neoplasms. A 54-year-old male had initially presented with a painless, left neck mass for 3 months. He underwent left thyroid lobectomy via a median sternotomy approach. Carcinoma showing thymus-like differentiation was the final histopathologic diagnosis. After 36 months of follow-up, no evidence of recurrence was observed. A median sternotomy is an excellent approach for CASTLE with anterior mediastinum involvement. Complete resection is important to improve the long-term survival rate and the locoregional recurrence rate.

Carcinoma showing thymus-like differentiation (CASTLE) with neuroendocrine differentiation

Carcinoma showing thymus-like differentiation (CASTLE) is a rare malignant neoplasm that histologically resembles thymic carcinoma and arises in the thyroid gland or adjacent soft tissue of the neck. Herein is reported the case of a 62-year-old male patient with CASTLE exhibiting neuroendocrine differentiation, who was treated with total pharyngolaryngo-esophagectomy and total thyroidectomy. Gross examination of the surgical specimen showed a grayish-white, solid, lobulated tumor, mainly located between the trachea and esophagus, and involving the lower part of the left thyroid lobe. Histologically, the tumor consisted of epithelial cell nests separated by thick fibrous septa. The tumor cells were polygonal in shape, and contained pale cytoplasm and a vesicular nucleus with prominent nucleoli. There were few mitotic figures. Rosette-like arrangements that suggested neuroendocrine differentiation were observed in part of the tumor. The tumor cells were positive for CD5 and neuroendocrine markers including synaptophysin and chromogranin A.

[Thyroid carcinoma with thymus-like differentiation (CASTLE): case report and review of the literature]

Carcinoma with thymus-like differentiation (CASTLE) is a rare malignant epithelial tumor which arises on soft tissue of the neck or thyroid gland. It is important to differentiate CASTLE from primary or metastatic squamous cell carcinoma of head and neck, and from squamous cell thyroid carcinoma, because it has a different prognosis. CD5 immunoreactivity might be helpful in CASTLE diagnosis. CASTLE behaves generally in an indolent fashion, even though it has a high relapse rate, while the other have a dismal prognosis due its high dissemination rate. Treatment includes surgical excision and radiotherapy. Chemotherapy can be offered, although its efficacy is not clear. Authors present a case of a 52 year-old male that complaints with cough, disphony, asthenia, and thyroid mass. Thyroidectomy was performed and the pathology revealed a CASTLE. After radiotherapy and chemotherapy, minimal response was obtained. The authors intend to discuss the differential pathologic diagnosis and the best therapy of this indolent but recurrent neoplasm, that demands strict long term follow-up.

Primary squamous cell carcinoma of the thyroid: report of three cases

We report three cases of squamous cell carcinoma of the thyroid, which is an unusual malignant tumor that needs to be distinguished from other thyroid pathologies due to its aggressive behaviour. Three men, with an average of 63 years old, presented with progressive enlargement in the neck, hoarse voice or weight loss. Physical and radiological examinations revealed clues where malignancy was suspected and surgical resections were performed. Histopathological examination of the specimens was diagnosed as squamous cell carcinoma. Proper workup excluded the possibility of any primary site of SCC other than the thyroid. All patients died within 5 months. Adjuvant therapy evaluation is still inconclusive. Complete surgical resection still remains the primary choice for cure. We believe that radical resection with clear surgical margins followed by adjuvant chemo-radiation therapy is a curative strategy for achieving any chance of long-term survival.

A six-year-old boy with a suspicious thyroid nodule: intrathyroidal thymic tissue

BACKGROUND

Ectopic intrathyroidal thymus tissue that forms mass lesions as a consequence of aberrant thymic migration during embryogenesis is rarely reported in the literature.

METHODS

We present the case of a 6-year-old boy with a right thyroid nodule and bilateral cervical lymph nodes. Thyroid hormone, antibodies, and routine chemistry tests were normal. Real-time thyroid ultrasound showed a right calcified nodule measuring 8 x 5 x 7 mm and multiple bilateral cervical lymph nodes. I131 scan showed mild decreased uptake in the right upper lobe. On fine-needle aspiration biopsy we discovered an atypical lymphoid proliferation that was suspicious, although not diagnostic, of a lymphoma. Immunostain for calcitonin was negative. Flow cytometry of the thyroid nodule aspirate demonstrated an abnormal polyclonal T cell population with dual expression of CD4 and CD8, and a subpopulation of cells that expressed TdT suggesting the possibility of lymphoblastic lymphoma. DNA analysis, as well as polymerase chain reaction for T cell and B cell gene rearrangement, did not demonstrate changes in the gene for the heavy chain of immunoglobulin of B cells and gamma chain of the T cell receptor. Lymph node aspirate showed unremarkable T and B lymphoid cells.

MAIN OUTCOMES

The diagnosis of ectopic intrathyroidal thymus was made after the operation.

CONCLUSION

Ectopic thymus tissue should be considered in the differential diagnosis of thyroid masses, especially in children.

Usefulness of S100A9 for diagnosis of intrathyroid epithelial thymoma (ITET)/carcinoma showing thymus-like differentiation (CASTLE)

AIMS

Intrathyroid epithelial tumour (ITET)/carcinoma showing thymus-like differentiation (CASTLE) is a rare malignant tumour, which is thought to originate from ectopic thymic tissue in the thyroid. The differential diagnosis between ITET/ CASTLE and squamous cell carcinoma (SCC) or undifferentiated carcinoma with squamoid component (UC-SCC) is very important, because ITET/CASTLE shows a far better prognosis than SCC or UC-SCC. In this study, we investigated the usefulness of S100A9, a marker of SCC and squamous cell epithelia, for diagnosis of ITET/CASTLE.

METHODS

We immunohistochemically investigated S100A9 expression in 23 ITET/CASTLEs, 26 SCCs, and 19 UC-SCCs, as well as eight thymomas and 12 normal thymic tissues.

RESULTS

All thymomas and thymic tissues showed a small number of S100A9-expressing cells in a scattered pattern in accordance with Hassall corpuscles. Twenty-one of 23 ITET/ CASTLEs showed the same pattern as thymomas or thymic tissues, while 14 SCCs and 15 UC-SCCs showed diffuse and laminated positivity of S100A9. The positive predictive value and specificity of S100A9 for diagnosis of ITET/CASTLE was 91.3 and 93.9%, respectively, and sensitivity was 75.0%.

CONCLUSIONS

These findings suggest that S100A9 is a useful marker for discriminating ITET/CASTLE from SCC or UC-SCC.

Carcinoma showing thymus-like element (CASTLE) of thyroid: combined modality treatment in 3 patients with locally advanced disease

OBJECTIVES

To examine the value of chemotherapy, radiotherapy and surgery for treatment of locally advanced carcinoma showing thymus-like element (CASTLE) of the thyroid.

METHODS

Retrospective analysis of 3 Chinese patients in a tertiary referral center in Hong Kong.

RESULTS

CASTLE is a rare thyroid malignancy with a frequency of only 0.15% (3/2033 patients) in our center. Three patients (M:F=2:1) aged 43, 49 and 62 years were studied. All 3 patients had advanced T4 disease with extensive tracheal infiltration and airway compression. None had lymph node or distant metastasis. Total thyroidectomy, combined with chemotherapy and radiotherapy, was effective in local control and symptom relief. Etoposide and carboplatin were tried in 2 patients with positive response. Neoadjuvant chemotherapy shrank the tumor rapidly and relieved symptoms of airway compression. All 3 patients had external radiotherapy resulting in good local control. In a patient with inoperable disease, chemotherapy and radiotherapy rendered the disease operable. All 3 patients were symptom-free and alive at 6, 2.5 and 1.8 years after diagnosis.

CONCLUSIONS

CASTLE is locally infiltrative and presents at advanced T stage in this small series. Chemotherapy and radiotherapy, apart from surgery, are effective treatment modalities. In cases of inoperable disease or advanced local disease, they can be employed in combination with surgery. Organ preservation of larynx and trachea may be achieved. Chemotherapy can be very useful for rapid relief of symptoms, especially in shrinking tumor to prevent airway obstruction.

Carcinoma showing thymus-like differentiation of the thyroid (CASTLE): a comparative study: evidence of thymic differentiation and solid cell nest origin

Carcinoma showing thymus-like differentiation (CASTLE) is a rare intrathyroidal neoplasm, a member of a tumor family probably arising from ectopic thymus or branchial pouch remnants. Thyroid solid cell nests (SCNs) may also be derived from branchial pouch remnants. SCNs express p63, carcinoembryonic antigen (CEA), and high molecular weight keratin (HMWK). To determine whether CASTLE and SCNs derive from similar embryologic origins/lines of differentiation, and to better differentiate CASTLE from other thyroid neoplasms, we compared p63, CD5, HMWK, and CEA staining of CASTLE and SCNs with other thyroid and thymic lesions. Seven CASTLE, 11 SCNs, 10 thymic carcinoma, 11 invasive thymoma, 12 thymoma, 28 papillary thyroid carcinoma, 4 thyroid squamous cell carcinoma, 2 childhood sclerosing carcinoma, 4 follicular adenoma, 6 follicular carcinoma, 4 poorly differentiated carcinoma, and 20 lymphocytic thyroiditis cases were analyzed. In normal thyroid, only SCNs stained for p63, HMWK, and CEA. The only CD5-positive cells in normal thyroid were T cells. Thymomas and normal thymus stained similarly to SCNs. All CASTLE and thymic carcinomas exhibited diffuse p63 and HMWK staining and all CASTLE cases and the majority of thymic carcinomas were positive for CEA and CD5. In contrast, none of the other thyroid neoplasms examined exhibited consistent staining for all 4 markers studied. These findings provide further evidence that CASTLE is distinct from other thyroid neoplasms, is probably of thymic origin, and may arise from branchial pouch remnants, the thyroid SCNs. Moreover CD5, HMWK, CEA and p63 can be used to help distinguish CASTLE from other thyroid neoplasms.

Pitfalls in thyroid tumour pathology

This review provides an itemized listing of major diagnostic pitfalls in the field of thyroid tumour pathology, emphasizing the features that the authors have found most useful in their recognition and avoidance.

Extrathyroid carcinoma showing thymus-like differentiation (CASTLE) tumor--a new case report and review of literature

BACKGROUND

We report a case of extrathyroid carcinoma showing thymus-like differentiation (CASTLE) tumor.

METHODS

A 47-year-old man had a left neck mass that gradually enlarged over approximately 3 months. Sonography and CT scans showed a soft tissue mass located at the left parapharyngeal space with displacement of left carotid artery and submandibular gland.

RESULTS

After total excision, the pathologic diagnosis was CASTLE tumor. The patient then received radiotherapy with a total dosage of 6600 cGy. After 21 months of postoperative follow up, there was no evidence of recurrence.

CONCLUSION

Generally, the treatment of choice is surgical excision with or without radiotherapy. Because CASTLE tumors have been reported to be radiosensitive, however, and because local recurrence is common, surgical excision with postoperative radiotherapy is suggested.

Carcinoma with thymus-like differentiation arising in the dermis of the head and neck

Carcinoma exhibiting thymus-like differentiation (CASTLE) is a rare, distinct tumor of the thyroid gland or soft tissue of the head and neck that may simulate primary squamous cell carcinoma or lymphoepithelioma, and which contains features reminiscent of thymic differentiation including Hassall's corpuscles, occasional perivascular spaces, and the presence of lymphocytes. Ectopic thymic tissue may result from incomplete descent or persistence of the cervical portion of the thymus and may occur anywhere along the course of the embryonic descent from the angle of the mandible to the sternal notch. Herein, we report two cases of dermal extrathyroidal CASTLE. The differential diagnosis of squamoid carcinoma with features of thymic differentiation includes extrathyroidal CASTLE, a primary squamous cell carcinoma with thymic differentiation, lymphoepithelioma-like carcinoma of the skin, and metastatic squamous cell carcinoma of unknown primary. It is essential that the latter two be ruled out before accepting the diagnosis of an extrathyroidal carcinoma with thymus-like differentiation.

A case of malignant thymoma mimicking thyroid carcinoma: a pitfall in fine-needle aspiration

A case of malignant thymoma presenting as an anterior neck mass is reported. The tumor extended from the thyroid gland to the superior mediastinum. It did not accumulate Tc-99m pertechnetate, but continued to accumulate Tl-201 at the late phase. A fine-needle aspiration cytology from the tumor showed tight clusters of epithelial cells with crowded ovoid nuclei. The tumor was initially diagnosed as thyroid carcinoma, clinically and cytologically. A thymoma with a dominant epithelial component has to be considered in the differential diagnosis of a suspected papillary carcinoma of the thyroid.

Carcinoma showing thymic-like elements--a rare malignancy of the thyroid gland

BACKGROUND

Carcinoma showing thymic-like elements (CASTLE) is a rare tumour of the thyroid of thymic origin. The histological appearance of this tumour may be similar to that of squamous cell carcinoma of the thyroid, but outcome associated with CASTLE is more favourable.

METHODS

A systematic literature review was conducted for case reports on CASTLE. A text word search of the Medline database was made with a manual search of the citations from these references. Twenty-two case reports were found.

RESULTS

In five patients with tumour-negative lymph nodes no local or distant recurrence was observed. Seventeen patients had unknown or involved lymph nodes. Two patients were excluded from further study: one had no follow-up and one was treated by irradiation only. Of the remaining 15, six had local, three had distant and two had local and distant recurrence. In patients with involved or unknown lymph node status, local recurrence was noted in one of five patients treated by surgery and irradiation, and in seven of ten patients treated by surgery alone. Irradiation or systemic chemotherapy was given to four patients with recurrent tumours, with variable response.

CONCLUSION

CASTLE with tumour-negative lymph nodes has a low risk of recurrence and surgery without adjuvant therapy is sufficient. Radiotherapy seems indicated when lymph nodes are tumour positive and can be effective for recurrent tumours. In selected patients surgery for recurrent tumour can improve quality of life and outcome.

Benign cervical thymoma masquerading as a malignant thyroid nodule

A thymoma in the neck region is a rare diagnosis involving a solitary neck nodule that moves with deglutition and is contiguous with the thyroid gland. The authors report an unusual case of a thymoma that accumulated both Tc-99m pertechnetate and Tc-99m MIBI. This is probably the first reported case of a benign neck thymoma concentrating these two radiopharmaceuticals. Thymoma should be added to the gamut of false-positive findings in the neck for thyroidal (with Tc-99m pertechnetate) and malignant (with Tc-99m MIBI) tissue.

Primary squamous cell carcinoma of the thyroid gland: an entity with aggressive clinical behaviour and distinctive cytokeratin expression profiles

AIMS

Primary squamous cell carcinoma of the thyroid gland is uncommon. This study aims to identify the clinicopathological features and the pattern of expression of cytokeratins and oncoproteins in this tumour.

METHODS AND RESULTS

Histological slides from Chinese patients with thyroid cancer treated in our institution from 1980 to 1999 were reviewed. Patients with primary squamous cell carcinoma of the thyroid were identified and their clinical records were analysed. The expression of cytokeratins (CKs), p53 and p21 in these cases were also studied by an immunohistochemical method. Four women (mean age 71 years) with squamous cell carcinoma of thyroid were found. The main presenting features were signs and symptoms of airway obstruction in three patients and neck swelling in one. The tumours were located at the right lobe (n=2), left lobe (n=1) or in both lobes of the thyroid (n=1). One patient died shortly after admission and the other three died within 4 months after thyroidectomy. The p53 protein was positive in 50% (2/4) of the tumours and p53+ tumours were poorly differentiated. The tumours were negative for p21. CK19 was expressed in all the tumours while CK7 expression was noted in 3/4 of the tumours. One carcinoma showed focal positivity to CK18. The tumours were negative for CKs 1, 4, 6, 10/13 and 20. The pattern of cytokeratin expression in squamous cell carcinoma of the thyroid gland was different from carcinoma showing thymus-like differentiation (CASTLE) of the thyroid gland and oesophageal squamous cell carcinoma.

CONCLUSIONS

Squamous cell carcinoma of the thyroid has aggressive clinical behaviour and characteristic CK expression pattern. p53 over-expression in these tumours was associated with tumour differentiation.