Thyroid thymoma in childhood

Aberrant Intrathyroid Tissue: a Report of Intrathyroid Lymph Node Metastasis and a Review of Literature

Aberrant histological elements have been infrequently reported to exist within the intact thyroid gland. In addition to distant metastases to the thyroid, a number of ectopic tissue rests and unusual cysts have been described within the thyroid gland. In this article, we report the presence of a true intrathyroid lymph node and describe the first reported case of intrathyroid lymph node metastasis of papillary thyroid cancer. Other reported aberrant intrathyroid tissues, possible pathophysiology, diagnostic features and surgical implications are also discussed.

Ectopic Hamartomatous Thymoma

The authors report an example of an unusual lower neck lesion, ectopic hamartomatous thymoma. Like other examples of this entity, the lesion was well marginated and characterized by cysts lined by squamous epithelium, adipose tissue, and spindle cells. The lesion was initially mistaken for a malignant neoplasm (at the time of frozen section) and the correct interpretation was rendered upon review of the permanent sections. They review the literature and clinicopathologic differential diagnosis of this entity.

Spindle Epithelial Tumor with Thymus-like Element (SETTLE), a Primary Thyroid Tumor

A 49-year-old female presented with a nontender mass in the neck. Fine-needle aspirate revealed spindle cells in a vaguely whorled pattern. The cells were fairly uniform and had elongated nuclei with fine chromatin. It was diagnosed as a cellular spindle cell neoplasm of uncertain histogenesis. Total thyroidectomy was performed revealing a well-circumscribed mass in the right lower pole extending substernally for 2 cm. The tumor was highly cellular and characterized by fascicles of spindle cells, focally displaying a biphasic pattern. The glandular component had a tubopapillary pattern. Occasional small mucous cysts were found adjacent to the tumor and in the opposite lobe, suggesting that the tumor might have arisen from the epithelial inclusions or remnants of branchial pouch within the thyroid. The spindle cells were immunoreactive for cytokeratin, epithelial membrane antigen, and vimentin and negative for thyroglobulin, calcitonin, chromogranin, desmin, myoglobin, and actin. Ultrastructurally, the spindle cells had abundant tonofilaments and well-developed desmosomes. These findings are consistent with a newly described entity, spindle epithelial tumor with thymus-like element (SETTLE), an intrathyroid lesion with a potential for delayed metastasis. Int J Surg Pathol 4(3):00-00, 1997

Spindle epithelial tumor with thymus-like differentiation (SETTLE): clinical-pathological features, differential pathological diagnosis and therapy

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a very rare tumor of the thyroid gland. An algorithm for the diagnosis and treatment of SETTLE has yet to be established. The aim of this study was to identify all case reports of SETTLE and to compare the clinical-pathological features and therapy of the cases identified. We performed a PubMed search for case reports of SETTLE in English published up to November 2014 in which "SETTLE" and "Spindle epithelial tumor with thymus-like differentiation" were keywords. We identified 35 articles for a total of 42 cases. We found that SETTLE usually occurs in children and adolescents as an asymptomatic neck mass. Thyroid function tests and tumor markers are invariably within normal range in all patients, and fine needle aspiration biopsy is rarely diagnostic for SETTLE. All 42 patients had undergone thyroidectomy. After surgical resection, chemotherapy (adjuvant or first/second-line treatment) and/or radiotherapy were administered to control tumor growth in cases with metastatic involvement. Although SETTLE presents a low-grade malignancy, it can metastasize to lymph nodes, the mediastinum, lung, vertebrae, and kidney even many years after the initial diagnosis. SETTLE may have a good prognosis if appropriately treated at initial presentation and if patients undergo long-term monitoring with regular clinical and morphological evaluations.

Thyroid spindle epithelial tumor with thymus-like differentiation (SETTLE): case report and review

Spindle epithelial tumor with thymus-like element (SETTLE) is a rare malignant neoplasm of the thyroid, occurring predominantly in children, adolescents, and young adults. SETTLE usually presents itself as a thyroid mass, without metastases at diagnosis. It is believed to derive from branchial pouch or thymic remnant tissue showing primitive thymic differentiation. This article reports the clinical, cytological, histological and immunohistochemical features of a SETTLE in a 3-year-old girl. Microscopic exam revealed a nodular, highly cellular neoplasm displayed in the classic biphasic pattern, with mixture of prominent spindle cell component and a minor glandular component lined by mucinous or respiratory-type epithelium. The immunohistochemical study showed strong and diffuse positivity for pan-CK, vimentin and smooth muscle actin. The present case is the first SETTLE case reported in Brazil. To date, the patient described remains without evidence of recurrence or metastasis 5 years after surgery.

Spindle epithelial tumor with thymus-like differentiation (SETTLE): Youngest reported patient

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a very rare thyroid tumor. It is one of a family of tumors arising either from ectopic thymus or remnants of branchial pouches that retain the potential to differentiate along the thymic line. Herein is reported a case of SETTLE in a 2-year-old girl. The patient underwent right thyroid lobectomy for a tumor of the right thyroid lobe. The resected specimen of this tumor revealed a whitish and solid mass. On microscopy, the tumor exhibited an area of spindle cells, glandular epithelium, and mucinous cystic lesions. The following findings were obtained on immunohistochemistry: the spindle cell area was diffusely positive for cytokeratin AE1/3 and vimentin, and partially positive for alpha-smooth muscle-specific actin. The glandular structures consisted of columnar cells and the cystic area was also positive for cytokeratin AE1/3. All three components of the tumor were negative for thyroglobulin, thyroid transcription factor-1, S-100 protein, carcinoembryonic antigen, somatostatin, synaptophysin, and chromogranin A. On the basis of the aforementioned findings, SETTLE was diagnosed. The patient remains disease free to date, 2 years after surgery with no additional treatment. To the best of the authors' knowledge the present SETTLE patient is the youngest yet reported.

Early metastasizing spindle epithelial tumor with thymus-like differentiation (SETTLE) of the thyroid

Spindle epithelial tumor with thymus-like elements is a rare thyroid lesion of children and young adults thought to be derived from branchial pouch remnants or foci of ectopic thymus. The lesion is poorly understood, and although it was originally believed to follow an indolent clinical course, its potential for late metastasis is becoming generally acknowledged. We have recently seen a unique case of this rare tumor in an 11-year-old boy, in which an unexpected and salient feature is the presence of a micrometastasis in a single lymph node at presentation. With the exception of 1 case with extensively infiltrative tumor and metastatic disease at the time of onset, in all other cases dissemination occurred years after surgical resection of the primary lesion. We review all previously reported cases and provide a detailed study of the histologic and ultrastructural appearances of this lesion.

Spindle epithelial tumor with thymus-like differentiation of the thyroid: a case report with pathological and molecular genetics study

We report an unusual case of spindle epithelial tumor with thymus-like differentiation (SETTLE) of the thyroid present in a 6-year-old boy. The tumor, located at both the left lobe and isthmus, was a circumscribed mass with slightly gritty whorled appearance. Microscopically, the lobulated, highly cellular, spindle cell neoplasm was arranged in intersecting bundles and fascicles separated by fibrous bands. Benign-appearing glands entrapped within fibrous bands and foci of squamous differentiation within spindle cells were observed. Immunohistochemically, the spindle cells were diffusely positive for cytokeratins, vimentin, and alpha-smooth muscle actin and patchily reactive for muscle-specific actin and epithelial membrane antigen, exhibiting myoepithelial differentiation. The spindle cells were also patchily immunopositive for p53 protein. Molecular genetic analysis revealed Ki-ras gene mutations at codons 13 (GGC(gly) to AGC(ser)) and 15 (GGC(gly) to AGC(ser)) on the same allele. Mutation of the p53 gene was not detected. This is the first report on Ki-ras oncogene mutations in a case of SETTLE.

Spindle epithelial tumor with thymus-like differentiation (SETTLE) of the thyroid

BACKGROUND

Tumors of the so-called intrathyroidal epithelial thymoma type are a rare group of thyroid neoplasm tumors. Of this type of tumor, spindle epithelial tumor with thymus like differentiation (SETTLE) has been reported only 17 times in English literature.

METHODS

An 18-year-old woman was initially seen with a 6-cm left thyroid mass that was resected with a left thyroidectomy. Histopathologic features of the excised left thyroid tumor together with an immunohistochemistry and electron microscopy led us to a diagnosis of SETTLE.

RESULTS

Most of the specimen was composed of highly cellular spindle cells that formed intersecting and streaming fascicles. The spindle cells showed both vimentin immunoreactivity and cytokeratin immunoreactivity but no immunoreactivity for thyroglobulin or calcitonin. Electron microscopic examination of the spindle cells demonstrated prominent cytoplasmic tonofilaments, desmosomes, and basal lamina consistent with epithelial cell origin. DNA content analysis by flow cytometry revealed DNA diploidy.

CONCLUSIONS

SETTLE of thyroid gland is an extremely rare entity. A review of the literature reveals that SETTLE has distinctive morphologic features and an immunohistochemical profile.

Spindle epithelial tumor with thymus-like differentiation (SETTLE): a distinctive malignant thyroid neoplasm with significant metastatic potential

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a very rare tumor of the thyroid believed to be derived from branchial pouch or thymic remnants and showing primitive thymic differentiation. Although this tumor is prone to develop delayed blood-borne metastases, the metastatic risk is unclear because the case reports in the recent literature had very short follow-up periods. We report one case, the oldest patient reported so far, who had been followed up until death. The 59-year-old man had an enlarged thyroid for all of his adult life, and presented with recent rapid enlargement of the thyroid. Neck exploration revealed a hard tumor in the right lobe, with adhesion to sternothyroid muscle. Histologic examination showed an invasive biphasic neoplasm traversed by sclerotic septa. Tight to loose fascicles of bland-looking spindly cells were intimately intermingled with tubulopapillary structures, diagnostic of the SETTLE. This patient developed left pulmonary metastases at 2 years and subsequently developed bilateral pulmonary and widespread metastases. He died 8 years after initial presentation. This case illustrates the protracted clinical course of the tumor, and survival for many years despite the occurrence of metastases. Review of the literature shows that SETTLE occurs predominantly in young patients with a median age of 15 years and male predominance. There is a significant metastatic rate of 71% for patients with more than 5 years of follow-up in spite of the otherwise indolent nature of the tumor.

Spindle epithelial tumor with thymus-like differentiation (SETTLE) of the thyroid with prominent mitotic activity and focal necrosis

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a rare, apparently low-grade spindle cell tumor of the thyroid gland occurring in young individuals and thought to be derived from thymic or branchial pouch remnants. Spindle epithelial tumor with thymus-like differentiation has little to no mitotic activity, and focal necrosis has been reported in one case. We present a case of SETTLE in a 29-year-old man that was initially evaluated by fine-needle aspirate biopsy and ultimately found to be consistent histologically with SETTLE. In this case, there were numerous mitotic figures among the spindle cells and focal necrosis. Spindle epithelial tumor with thymus-like differentiation has been considered to be a tumor of low malignant potential with metastases developing some years after diagnosis. This is the first case in which prominent mitotic activity and necrosis is reported perhaps representing an aggressive variant.

Spindle epithelial tumour with thymus-like element (SETTLE): the predominantly monophasic variant

AIMS

To describe two cases of spindle epithelial tumour with thymus-like element (SETTLE) which are composed predominantly of spindle cells. In addition, to highlight some unusual histological features in SETTLE and discuss its separation from histological mimics.

METHODS AND RESULTS

The thyroid masses were in a 4-year-old boy and a 25-year-old male. Both patients were euthyroid and were well except for thyromegaly. The specimens were formalin fixed, and immunohistochemistry was performed on this material using a panel of antibodies following microwave antigen retrieval. Morphologically, the dominant pattern was of sheets of spindle cells arranged in several patterns. There was mild pleomorphism and occasional mitoses. There were very small foci of squamous epithelium and occasional ductular structures. The stroma was composed of fibrous tissue and isolated areas of calcification were noted. The spindle cells showed strong and diffuse immunoreactivity with AE1/3, CAM5.2 and vimentin.

CONCLUSION

We describe two cases of SETTLE that are composed mainly of spindle cells and only a very focal ductular component. In addition, calcification was noted within the stroma in one of the cases. These predominantly spindle examples of SETTLE must be separated from synovial sarcoma, which is a more mitotically active, aggressive tumour displaying only patchy immunopositivity with epithelial markers.

Tumors of the neck showing thymic or related branchial pouch differentiation: a unifying concept

A number of rare tumors occurring in the soft tissues of the neck and the thyroid gland, reported in the literature under a variety of designations, show complete to partial histologic resemblance to the fetal, mature, or involuted thymus and mediastinal thymomas. This family of tumors spans a range of histologic appearances and behaviors from completely benign lesions to metastasizing malignant tumors. After reviewing the previously reported and new cases, we have been able to delineate four reasonably well-defined clinicopathologic entities within this spectrum. On the benign end is "ectopic hamartomatous thymoma," which occurs in the soft tissues of the lower neck. It is characterized by spindle epithelial cells, solid or cystic epithelial islands, and adipose cells which intermingle haphazardly to impart a hamartomatous quality. In the middle of the spectrum are the ectopic cervical thymomas which are usually benign, but can sometimes be locally invasive and can exceptionally metastasize. They are histologically identical to mediastinal thymomas, and residual ectopic thymus is not uncommonly identifiable in the periphery of the tumor. On the malignant end are tumors we have designated as "spindle epithelial tumor with thymus-like differentiation" (SETTLE) and "carcinoma showing thymus-like differentiation" (CASTLE). Tumors of the SETTLE type occur in the thyroid gland of young patients, and are highly cellular tumors comprised of compact bundles of long spindle epithelial cells which merge with tubulopapillary structures and/or mucinous glands. Tumors of the CASTLE type are histologically similar to thymic carcinoma of the lymphoepithelioma or squamous cell variety. We postulate that this family of tumors arises either from ectopic thymus or remnants of branchial pouches which retain the potential to differentiate along the thymic line.