Diagnostic use of PAX8, CAIX, TTF-1, and TGB in metastatic renal cell carcinoma of the thyroid

Tumor-to-tumor spread: a case report and literature review of renal cell carcinoma metastasis into thyroid cancer

Tumor-to-tumor metastasis is a rare, yet important entity. Patients with a history of renal cell carcinoma (RCC) may have tumor deposits to the thyroid gland preceding or following their initial cancer diagnosis for many years. The diagnosis can be challenging, and clinicians must remain suspicious of a newly found thyroid nodule in a patient with a history of RCC. In this review, we report a case of a patient with RCC who was incidentally found to have a thyroid nodule on surveillance imaging found to be consistent with tumor-to-tumor metastasis from RCC into papillary thyroid carcinoma. It is imperative to consider this diagnosis as the thyroid is the most common site of spread, and treatment with partial or total thyroidectomy has led to improved survival.

Metastatic renal cell carcinoma to the thyroid with cervicothoracic venous tumor thrombosis

INTRODUCTION

Metastatic renal cell carcinoma (RCC) represents 25%-42% of metastatic thyroid malignancies. Propensity for RCC to demonstrate intravascular extension to the inferior vena cava is well documented. We present an analogous phenomenon of intravascular extension to the internal jugular vein (IJV) from thyroid gland metastasis.

METHODS

A 69-year-old male presented with metastatic RCC of the right thyroid lobe. Imaging demonstrated tumor thrombosis of the ipsilateral IJV, extending inferiorly to the junction of the brachiocephalic, subclavian, and internal jugular veins within the mediastinum.

RESULTS

Surgical excision required control of both the IJV in the neck and mediastinal venous great vessels via sternotomy, prior to subtotal thyroidectomy and venotomy for en bloc resection.

CONCLUSION

This case report describes metastatic RCC to the thyroid gland with cervicothoracic venous tumor thrombosis successfully treated with subtotal thyroidectomy, sternotomy for venotomy and tumor thrombectomy, and preservation of IJV conduit.

Top 10 Clear Cell Head and Neck Lesions to Contemplate

BACKGROUND

Optically clear cytoplasm may occur in neoplastic and non-neoplastic conditions, either as a characteristic feature of a disease entity or as a morphologic rarity, potentially creating diagnostic dilemmas in various organ systems. In the head and neck, clear cell change can occur in lesions of salivary, odontogenic, thyroid, parathyroid, or sinonasal/skull base origin, as well as in metastases to these regions.

METHODS

This review elaborates the top ten clear cell lesions in the head and neck, emphasizing their distinguishing histologic, immunohistochemical, and molecular attributes, and presents a rational approach to arriving at an accurate classification.

RESULTS

Cytoplasmic pallor or clearing may be caused by accumulations of glycogen, lipid, mucin, mucopolysaccharides, water, foreign material, hydropic organelles, or immature zymogen granules. Overlapping morphologic features may present a diagnostic challenge to the surgical pathologist. Similarity in immunohistochemical profiles, often due to common cell type, as well as rare non-neoplastic mimics, furthers the diagnostic conundrum.

CONCLUSIONS

The top ten lesions reviewed in this article are as follows: (1) clear cell carcinoma (salivary and odontogenic), (2) mucoepidermoid carcinoma, (3) myoepithelial and epithelial-myoepithelial carcinoma, (4) oncocytic salivary gland lesions, (5) squamous cell carcinoma, (6) parathyroid water clear cell adenoma, (7) metastatic renal cell carcinoma (especially in comparison to clear cell thyroid neoplasms), (8) sinonasal renal cell-like adenocarcinoma, (9) chordoma, and (10) rhinoscleroma.

Preoperative, Intraoperative, and Postoperative Parathyroid Pathology: Clinical Pathologic Collaboration for Optimal Patient Management

Parathyroid disease typically presents with parathyroid hyperfunction as result of neoplasia or a consequence of non-neoplastic systemic disease. Given the parathyroid gland is a hormonally active organ with broad physiologic implications and serologically accessible markers for monitoring, the diagnosis of parathyroid disease is predominantly a clinical pathologic correlation. We provide the current pathological correlates of parathyroid disease and discuss preoperative, intraoperative, and postoperative pathology consultative practice for optimal patient care.

Immunohistochemical Panels to Evaluate Important Immunophenotypes of Human Mesonephros

Background. The immunophenotypes and potential excretory function of human mesonephros are not well studied. Methods. Five mesonephros specimens of human embryos from the 6^th to 10^th weeks of gestation were stained with immunohistochemical markers. Results. PAX8 was universally expressed in all renal tubules, while α-methyacyl-CoA racemase (AMACAR) was positive in proximal tubules and GATA3 was positive in distal tubular mesonephric structures. At the 8th weeks of gestation, the mesonephric glomeruli were characterized by opened glomerular capillary loops with Periodic Acid Schiff (PAS)-positive glomerular basement membranes and GATA3-positive mesangial-like cells. By the 8^th week, proximal tubules showed PAS-positive brush borders, indicating reabsorption capacity, and the proximal tubules also demonstrated positivity with kidney injury molecule-1 (KIM-1), representing tubular response to injury. Conclusion. Our overall findings show detailed phenotypes of the glomerular and tubular structures of the mesonephros and indicate that at the 8^th week of gestation, the mesonephros may carry out temporary excretory function before metanephros becomes fully functional.

Identifying metastatic renal cell carcinoma in thyroid fine-needle aspirates by molecular testing

Renal cell carcinoma (RCC) is the most common type of cancer found to metastasize to the thyroid gland. These tumors may represent a diagnostic challenge in cytology. However, most RCC tumors carry VHL alterations, which are rare in primary thyroid tumors. The aim of this study was to evaluate the utility of molecular testing in detecting metastatic RCC in thyroid fine-needle aspiration (FNA) samples. From November 2017 until March 2022, thyroid FNA samples with ThyroSeq v3 results showing both VHL alterations and low/absent expression of thyroid cell markers were analyzed. Eighteen samples from 15 patients met the inclusion criteria. On molecular analysis, deleterious VHL mutations were found in nine (50%) nodules, VHL copy number alteration (CNA) in two (11%), and both mutations and CNA in seven (39%). None of the cases showed mutations commonly found in thyroid tumors. The mean age of these patients was 68 (range, 49-89) years with a male to female ratio of 2:1. Eight (53%) patients had multiple thyroid nodules on ultrasound. On cytology, 14 (78%) nodules were diagnosed as Bethesda III, 2 (11%) as Bethesda IV, and 2 (11%) as Bethesda V. At the time of cytology review, the history of RCC, sometimes remote, was available for ten patients. Of the 14 patients with medical history or surgical follow-up available, all had history of RCC or renal mass or revealed metastatic RCC on thyroidectomy. This study demonstrates that molecular testing can reliably identify metastatic RCC in thyroid nodules with indeterminate cytology, which could improve patient management.

Metastatic Clear Cell Renal Cell Carcinoma Involving the Thyroid Gland: A Clinicopathologic Study of 17 Patients

Background. Metastatic clear cell renal cell carcinoma (RCC) is one of the most common secondary thyroid malignancies. Diagnosis can be challenging, particularly if presenting many years after initial diagnosis. We reviewed clinicopathologic features and immunoprofile of metastatic clear cell RCC in thyroid. Design. We identified 17 patients from 2003-2021. Clinical data were obtained from medical records, and slides were retrieved and reviewed. Results. Seventeen patients (12 male and 5 female) included 12 thyroidectomies, 3 core biopsies, 1 excisional biopsy, and 1 fine-needle aspiration. The average patient age was 68.7 years (range, 45-88 years). Sixteen patients had history of clear cell RCC, and in 1 patient, the clear cell RCC was discovered after the thyroid metastasis was found. Thyroid gland metastases were on average diagnosed 90.7 months after the diagnosis of the renal primary (range, 24-240 months). Patients presented with a new palpable mass (n = 11) or dyspnea/stridor (n = 1). Five tumors were incidentally found via surveillance imaging. In 2 patients, metastases occurred within follicular thyroid neoplasms. All metastases showed conspicuous sinusoidal vasculature between the tumor nests and areas of myxoid degeneration. A prominent thick fibromuscular pseudocapsule was evident in 10 resections. Immunohistochemistry (n = 5) showed that the metastases were positive for PAX8, CA9, and CD10, while negative for keratin 7, thyroglobulin, and TTF1. Conclusions. Metastatic clear cell RCC involving the thyroid gland is infrequent and typically occurs remotely after the initial diagnosis. Cytologic and histologic features may show significant overlap with primary thyroid lesions. Immunohistochemistry can help reliably distinguish metastases from primary thyroid neoplasms.

Carcinoma of Unknown Primary Origin: Application of Immunohistochemistry With Emphasis to Different Cytokeratin 7 and 20 Staining Patterns

BACKGROUND

Although the primary origin of some carcinomas may be obscure to clinicians, its identification is crucial as it affects prognosis and treatment (especially novel targeted therapies). Immunohistochemistry (IHC) may be helpful in identifying the primary origin of carcinomas. This retrospective survey aimed to evaluate the frequency and accuracy of each IHC marker used to determine the origin of carcinomas.

METHODS

The review of pathology department archives revealed 307 cases of cancer of unknown primary origin (CUP) between 2015 and 2020, which were accessible in the department archives. Demographic information, site of biopsy, clinical and pathologic diagnoses, and IHC results of the patients were collected.

RESULTS

The patients included 157 (51.15%) men and 150 (48.85%) women. The age of the patients ranged from 14 to 92 years, including 106 (34.5%) expired cases. In 27% of cases, the primary origin of carcinoma remained unknown. The agreement between pathologic and clinical diagnoses was 59%. The most common pattern of cytokeratin (CK) expression in CUP was CK7+/CK20- (55.3%), followed by CK7-/CK20- (19%), CK7+/CK20+ (15%), and CK7-/CK20+ (10.7%), respectively.

CONCLUSION

The IHC analysis may improve the diagnosis of CUPs. However, the origin of some cases remains unknown despite an IHC analysis, thereby necessitating the use of more diagnostic procedures or gene expression studies for reaching a definitive diagnosis.

Clinicopathological and Molecular Features of Secondary Cancer (Metastasis) to the Thyroid and Advances in Management

Secondary tumours to the thyroid gland are uncommon and often incidentally discovered on imaging. Symptomatic patients often present with a neck mass. Collision tumours of secondary tumours and primary thyroid neoplasms do occur. Ultrasound-guided fine-needle aspiration, core-needle biopsy, and surgical resection with histological and immunohistochemical analysis are employed to confirm diagnosis as well as for applying molecular studies to identify candidates for targeted therapy. Biopsy at the metastatic site can identify mutations (such as EGFR, K-Ras, VHL) and translocations (such as EML4-ALK fusion) important in planning target therapies. Patients with advanced-stage primary cancers, widespread dissemination, or unknown primary origin often have a poor prognosis. Those with isolated metastasis to the thyroid have better survival outcomes and are more likely to undergo thyroid resection. Systemic therapies, such as chemotherapy and hormonal therapy, are often used as adjuvant treatment post-operatively or in patients with disseminated disease. New targeted therapies, such as tyrosine kinase inhibitors and immune checkpoint inhibitors, have shown success in reported cases. A tailored treatment plan based on primary tumour features, overall cancer burden, and co-morbidities is imperative. To conclude, secondary cancer to the thyroid is uncommon, and awareness of the updates on diagnosis and management is needed.

Metastatic thyroid carcinoma mimicking as a primary neoplasia of the kidney: A case report

The unfavorable behavior of primary thyroid carcinoma (PTC) has been revealed by the hematogenous distant metastases in ~20-25% of cases with frequent localizations in lungs and bones, but infrequently in kidney. A 69-year-old male patient was admitted to Department of Human Pathology in Adulthood and Childhood 'G. Barresi', University Hospital G. Martino, (Messina, Italy) for an incidentally detected parenchymal mass involving the right kidney. A partial nephrectomy was done; at the post-surgical examination, a large nodular grayish mass was documented. Microscopically, a diffuse proliferation with solid/follicular pattern with some colloid-filled spaces was appreciable. An intense immunopositivity was revealed for thyroglobulin, thyroid transcription factor-1 (TTF-1), paired-box gene 8 (PAX-8) and cytokeratin 7, while CD10 and renal cell carcinoma marker were negative. A diagnosis of the metastatic thyroid follicular carcinoma localized in the kidney was made. At ultrasound examination, a hyperechoic mass extending from the left thyroid lobe to the isthmus, to which TIR4 diagnostic category according to the Italian reporting system for thyroid cytology was attributed. After thyroid surgical procedure, the final diagnosis of primitive differentiated follicular thyroid carcinoma with foci of poorly differentiated component was made.

Metastasis to the thyroid gland: a single-institution 16-year experience

AIMS

Metastasis to the thyroid gland is a rare occurrence that may pose a diagnostic challenge. In this study, we aimed to report the clinicopathological features, immunoprofile, molecular alterations and outcome of 30 patients treated at our centre from 2003 to 2019.

METHODS AND RESULTS

The most common site of the primary tumour was the kidney, followed by the lung, lower gastrointestinal tract and breast. In seven (23%) patients, the thyroid metastases were resected prior to the diagnosis of the primary tumours. Six patients (20%) had thyroid as the sole metastatic site. Three (10%) patients harboured tumour-to-tumour metastasis; 71% had a unilateral unifocal thyroid mass, which might be mistaken for a primary thyroid tumour. Among the 13 cases that were initially diagnosed at an outside hospital, four (31%) were misinterpreted as a thyroid primary. An immunohistochemical panel of thyroid follicular cell markers was most useful to differentiate primary thyroid tumours from metastasis. Molecularly, the metastasis showed alterations characteristic of the primary tumour, which may be helpful in establishing the diagnosis and primary site. Although the prognosis was poor, with a 5-year disease specific survival of 58%, a long-term cure was possible in cases with oligometastasis successfully treated with surgery.

CONCLUSIONS

Metastasis to the thyroid gland is an uncommon phenomenon, with an incidence of 0.36% in all thyroid malignancies. It may present as a solitary thyroid mass before the discovery of the primary tumour, posing a diagnostic challenge. Although the overall prognosis is poor, a subset of patients with oligometastasis can be managed surgically.

Clear cell change in follicular adenoma of the thyroid. A diagnostic challenge

Clear cells in thyroid neoplasms can take two main forms: balloon-shaped and signet-ring cells. Balloon-shaped cell change in follicular adenoma is rare. A review of the literature has revealed only 20 previously published cases. We report herein a new case in the right thyroid lobe of a 45-year-old man. The clinicopathological data of the 21 cases including our paper have revealed that the ages of the patients ranged from 22-70 years, with a mean of 41.6 years. There was a clear predominance in women (M:F, 1:6). The most frequent location was in either of both lobes (81.8%), rarely affecting the isthmus. One case was observed in an ectopic thyroid in the submandibular region. The size ranged from 0.7-5.5 cm (mean 2.9 cm). The type of surgical intervention where this data was reported it was lobectomy for 10 (55.5%) cases, thyroidectomy for six (33.3%) cases, and simple excision for two (11.1%) cases. In one patient, the lobectomy was accompanied by cervical lymph node dissection. No cases recurred or extended outside the thyroid. The main differential diagnoses include intrathyroidal clear cell tumor of parathyroid origin, clear cell carcinoma of follicular, oncocytic, papillary, medullary or undifferentiated (anaplastic) origin, paraganglioma, metastatic clear cell carcinoma, especially of renal origin, metastatic balloon cell melanoma, and clear large-cell lymphoma. A thyroid lesion showing clear cell change constitutes a diagnostic challenge in cytological and biopsy diagnosis. Careful observation of the routine techniques along with the aid of an adequate immunohistochemical panel is essential to reach a correct biopsy diagnosis.

Metastasis of renal cell carcinoma to the parathyroid gland 12 years after radical nephrectomy

Renal cell carcinoma (RCC) accounts for 2-3% of all malignant tumors in adults. RCC is well-known for its propensity to metastasize to unusual sites, and late metastasis, even after several years, is common. Involvement of the parathyroid gland has only four reported cases in literature. A 62-year-old Caucasian man was referred to our department due to an enlarging cervical mass. The patient's relevant past medical history included a left nephrectomy for RCC 12 years ago. After right thyroid lobectomy and isthmectomy, histopathology revealed an intrathyroidal nodule corresponding to the parathyroid gland with metastatic RCC. Approximately one-third of RCC subjects with apparently localized disease will develop metastasis, even several years after nephrectomy. The literature is sparse regarding the most appropriate follow-up approach for these patients. We describe a rare case of nodular goiter of the thyroid gland concurrent with metastatic RCC to an intrathyroidal parathyroid gland, without disseminated systemic metastasis.

Metastatic clear cell renal cell carcinoma to the thyroid gland: A clinico-pathological and immunohistochemical study of 8 cases and review of the literature

When a patient with a previous history of neoplasm presents with a thyroid lesion, the possibility of it being metastatic should always be considered. In this series, we present the clinicopathological and immunohistochemical features of the thyroid metastases diagnosed in our department over the past 30 years. Here we present eight thyroidal metastases from clear cell renal cell carcinoma (ccRCCC), including a tumor to tumor metastasis, the patients being 2 men and 6 women with a median age of 62 years. The majority had a past history of goiter and a single and palpable metastasis. In one patient the thyroid metastases were the first sign of the ccRCCC. In the available cases, the metastasis showed positivity to PAX8 and CAIX and negativity to TTF1 and thyroglobulin. The median time from the detection of the primary renal tumor to thyroid metastasis and from thyroidectomy to last follow up were 84.17 and 54.50 months, respectively. After a median follow up of 158.50 months none of the patients had died from ccRCCC. Renal cell carcinoma (RCC) is the most frequent malignant neoplasm of the kidney and its incidence has increased over recent decades. In a clinical series, up to 1-3% of the oncologic thyroidectomies were due to thyroid metastases and the most frequent metastasizing tumor was RCC, followed by lung and breast cancer.

Immunohistochemistry, carcinomas of unknown primary, and incidence rates

Pathologists use immunohistochemistry is their day-to-day practices to assist in distinguishing site of origin of metastatic carcinomas. Here, the work-up is discussed neuroendocrine carcinomas, squamous cell carcinomas and adenocarcinomas with particular attention to tumor incident rates and predictive values of the best-performing immunohistochemical markers.

Emerging entities in renal cell neoplasia: thyroid-like follicular renal cell carcinoma and multifocal oncocytoma-like tumours associated with oncocytosis

The list of accepted entities of renal cell neoplasia has burgeoned since the turn of the century through recognition of rare tumour types and the discovery of genetic mutations driving renal neoplasia syndromes. This growth has not finished and in this report we present examples of each of these types which were not included in the 2016 World Health Organization classification of renal neoplasia, but are candidates for inclusion in the next edition of the classification. Thyroid-like follicular renal cell carcinoma is a rare tumour type with a distinctive microscopic appearance resembling follicles of the thyroid gland. Thirty-nine cases have been described and the findings have been reasonably consistent. Oncocytoma-like tumours associated with oncocytosis arise as a result of somatic mutations in the mitochondrial genome. The differential diagnosis is mainly with the renal lesions of the Birt-Hogg-Dubé syndrome, which is the result of germline mutations in the folliculin gene. Patients with oncocytoma-like tumours associated with oncocytosis are at great risk of developing renal failure as the proliferating lesions replace the renal parenchyma. Oncocytoma-like tumours have never been found to metastasise.

Atypical Histiocytoid Cells in Metastatic Papillary Thyroid Carcinoma: An Underrecognized Cytologic Pattern

OBJECTIVES

Fine-needle aspiration (FNA) of head and neck lymph nodes (LNs) is useful in diagnosing metastatic papillary thyroid carcinoma (PTC) and most commonly shows classic cytologic features of PTC. Metastatic PTC, however, may occasionally present with a pattern unfamiliar to most pathologists: atypical histiocytoid cells (AHCs).

METHODS

All PTC thyroidectomy specimens with associated FNA of LNs were retrieved from our files for 2007 to 2013. We aimed to assess cytologic features of metastatic PTC, as well as the presence of AHCs and their morphology.

RESULTS

Fifty-six FNAs from LNs with metastatic PTC were reviewed. AHCs were identified in 38 (68%) cases, while only PTC with classic cytologic features was seen in 18 (32%) cases. AHCs did not show diagnostic nuclear features of PTC and presented as large cells with abundant cytoplasm either vacuolated or dense. Nuclei varied from vesicular with prominent nucleoli to dark and smudgy. Thirty-one cases showed mixed AHCs and classic PTC, but seven cases (13% of all metastatic PTCs in LNs) consisted only of AHCs.

CONCLUSIONS

AHCs are an often unrecognized metastatic morphologic pattern of cystic PTC, as it does not show diagnostic classic nuclear features of PTC. AHCs are the predominant cytologic finding in approximately 13% of metastatic PTCs to neck LNs.

Undifferentiated Malignant Neoplasm Involving Parotid and Thyroid: Sampling and PAX8 Cross-Reactivity Can Obscure the Diagnosis of Lymphoma

Poorly differentiated malignant neoplasia arising within the head and neck region may originate from diverse sources. We report a case of a cytologically undifferentiated malignant neoplasm clinically presenting as masses involving thyroid and parotid. Although PAX8 was immunoreactive and thus worrisome for anaplastic thyroid carcinoma, the tumor was eventually proven to represent PAX5 positive diffuse large B-cell lymphoma expressing cross-reactivity with polyclonal PAX8 antibody. Cross-reactivity between commercially available polyclonal PAX8 and PAX5 immunostains has been described in the literature but is not widely known, and it is a potential pitfall for making a misdiagnosis. This distinction can have importance in selection of subsequent clinical therapy and should be considered in choice of immunohistochemical stains for diagnostic purposes.

Intrathyroidal Clear Cell Tumor of Parathyroid Origin with Review of Literature

Water-clear cell adenoma (WCCA) of the parathyroid gland is an exceedingly rare neoplasm. To date, 17 cases have been reported in the literature, with only one of them being intrathyroidal. Here we report a case of a 34-year-old woman who presented for evaluation of a goiter and was found to have a thyroid nodule and abnormal thyroid function tests (TFT). Fine needle aspiration biopsy of the nodule revealed thyroid follicular cells without atypia and subsequent Afirma® Gene Expression Classifier (GEC) testing results were suspicious for malignancy. As a result, the patient underwent a right thyroid lobectomy and isthmusectomy. Histological sections revealed an intrathyroidal nodule consistent with a clear cell neoplasm of parathyroid origin. The histologic appearance together with the immune profile was diagnostic of WCCA, with diffuse positivity for GATA3, focal weak positivity for parathyroid hormone, and negativity for PAX8, thyroglobulin, TTF1, synaptophysin, chromogranin, and S100p. Our study focuses on the clinical presentation, current management strategies, and review of the available literature surrounding this rare diagnosis. The ultimate goal is to help endocrinologists and surgeons establish a foundational treatment plan for intrathyroidal clear cell tumor cases.

Acanthosis Nigricans associated with clear-cell renal cell carcinoma

Acanthosis nigricans (AN), an entity recognized since the 19th century, is a dermatopathy associated with insulin-resistant conditions, endocrinopathies, drugs, chromosome abnormalities and neoplasia. The latter, also known as malignant AN, is mostly related to abdominal neoplasms. Malignant AN occurs frequently among elderly patients. In these cases, the onset is subtle, and spreading involves the flexural regions of the body, particularly the axillae, palms, soles, and mucosa. Gastric adenocarcinoma is the most frequent associated neoplasia, but many others have been reported. Renal cell carcinoma (RCC), although already reported, is rarely associated with malignant AN. The authors report the case of a woman who was being treated for depression but presented a long-standing and marked weight loss, followed by darkening of the neck and the axillary regions. Physical examination disclosed a tumoral mass in the left flank and symmetrical, pigmented, velvety, verrucous plaques on both axillae, which is classical for AN. The diagnostic work-up disclosed a huge renal mass, which was resected and further diagnosed as a RCC. The post-operative period was uneventful and the skin alteration was evanescent at the first follow-up consultation. The authors call attention to the association of AN with RCC.

Mutations of TSHR and TP53 Genes in an Aggressive Clear Cell Follicular Carcinoma of the Thyroid

Clear cell follicular carcinoma is a rare type of thyroid cancer and some with aggressive biological behavior. The cytoplasmic clearing of the neoplastic cells has been attributed to the accumulation of various substances, such as glycogen, lipid, mucin, and thyroglobulin, or distension of mitochondria or endoplasmic reticulum. However, the molecular mechanisms responsible for the characteristic appearance of the cell cytoplasm and the biological behavior remain unknown. We report here a case of aggressive clear cell follicular carcinoma of the thyroid with molecular profile using targeted next generation sequencing (NGS) that presented as a metastatic tumor in a woman with a history of breast carcinoma. The NGS data revealed the coexisting of a well-characterized loss-of-function TP53 R248Q mutation and a putative gain-of-function mutation of TSHR L272V, which was suggested by the overexpression of thyroglobulin and SLC5A5 (NIS) genes in this tumor. TP53 mutations are usually related with dedifferentiation, progression, and metastasis of thyroid carcinomas. Identification of TP53 R248Q in this tumor correlated with its aggressive clinical behavior. Gain-of-function mutation of TSHR can overstimulate the thyroid follicular cells as the elevated level of TSH does and might have contributed to the development of clear cell morphology in this tumor. This report represents the first case of clear cell follicular carcinoma of the thyroid with NGS analysis and more molecular characterization is needed to elucidate the pathogenesis and provide more prognosis-relevant information for this uncommon variant of thyroid carcinomas.

Cytologic Features and Immunocytochemical Profiles of Malignant Effusions with Metastatic Papillary Thyroid Carcinoma: A Case Series from a Single Institution

OBJECTIVE

Malignant effusions due to papillary thyroid carcinoma (PTC) are rare, but portend a poor prognosis. PTC metastases, although rare, most frequently occur in the lungs and bone. Therefore, differentiating thyroid etiology of malignant effusions from other sites becomes clinically significant in patient management. This study examines morphologic and immunocytochemical findings in 5 cases of malignant effusions with PTC involvement.

STUDY DESIGN

The electronic database at the University of Michigan was searched from January 1, 1995 to December 31, 2014 for malignant pleural effusions with PTC involvement. Clinicopathologic data were obtained from electronic medical records. Cytologic slides were reviewed.

RESULTS

Five cases of malignant effusions due to PTC were identified. Characteristic cytologic features of PTC, including ovoid nuclei, irregular nuclear contours, and psammomatous calcifications, were seen. However, the predominant cytologic feature observed was moderate amounts of delicate to vacuolated cytoplasm within the tumor cells. A review of immunocytochemistry demonstrated that all 5 cases showed patchy to diffuse TTF-1 positivity and diffuse positivity for Pax-8. Thyroglobulin only showed focal to patchy positivity in 3 of 5 cases.

CONCLUSION

Given the morphologic features found in our case series, an immunocytochemical workup for the evaluation of involvement of an effusion by a thyroid primary is crucial for accurate diagnosis and appropriate clinical treatment.

Metastatic carcinoma of unknown primary: diagnostic approach using immunohistochemistry

Carcinoma of unknown primary origin (CUP) is one of the 10 most prevalent malignancies. CUP patients in whom a site of origin can be ascribed have better outcomes than those in which the primary tumor remains unidentified. Among the tools available to pathologists in approaching these lesions, immunohistochemistry is a reliable, inexpensive, and widely available resource. New markers continue to emerge, which, in combination with other historically useful antibodies, allow rapid and accurate identification of primary site in an increasing number of cases. This review discusses the approach to the diagnosis of CUP using immunohistochemistry and outlines some of the most useful markers with a particular focus on the utility of lineage-restricted transcription factors, including CDX2, NKX3-1, PAX8, SATB2, TTF-1, and SF1.

Metastatic carcinoma to the thyroid gland from renal cell carcinoma: role of ultrasonography in preoperative diagnosis

BACKGROUND

Patients with metastases to the thyroid from renal cell carcinoma (RCC) that need surgical management are not many and unfamiliar to clinicians and thyroid endocrinologists. Therefore, little information is available on ultrasonographic features of metastatic carcinoma in the thyroid. The strategic value of ultrasound in preoperative surgical planning for patients with thyroid nodules has become increasingly appreciated. The purposes of this article are to clarify the ultrasound characteristics of metastatic carcinoma to the thyroid from RCC by evaluating many patients in one institute, and to investigate the role of ultrasonography in preoperative diagnosis.

METHODS

Ten patients with these carcinomas who had undergone surgical management were investigated clinically and ultrasonographically. Ultrasonographic features to be evaluated were the form of involvement in the thyroid, size, shape, pattern, calcifications, vascularity, and tumor thrombus. Clinical features were previous history of RCC, serum thyroglobulin levels, cytology, preoperative diagnosis, and surgery.

RESULTS

Ultrasonographic features of these carcinomas were more likely to involve a solitary, irregular, and solid without calcifications, and prominent intra-tumoral vascularity and tumor thrombus in the vein. These patients tended to be older, and to have relatively late recurrence in the thyroid, RCC in the right kidney as the primary site, and relatively low serum thyroglobulin levels.

CONCLUSIONS

Metastatic carcinomas to the thyroid from RCC presented highly characteristic features on ultrasonography. These ultrasonographic features combined with cytological findings and previous medical history of RCC can provide the optimal process for the preoperative diagnosis of such patients.

Expression and diagnostic implications of carbonic anhydrase IX in several tumours with predominantly clear cell morphology

AIMS

High expression of carbonic anhydrase IX (CA IX) has been reported in clear cell renal cell carcinoma (ccRCC); few studies have reported CA IX expression in other tumours with predominantly clear cell morphology. The aim of study was to examine the expression and diagnostic implications of CA IX in these latter tumours.

METHODS AND RESULTS

An immunohistochemical study was performed of 159 tumours with predominantly clear cell morphology. The results showed that, in addition to primary (25/25) and metastatic (10/11) ccRCC, CA IX was also expressed in breast (2/2), pulmonary (3/5) and hepatic (1/4) clear cell carcinoma, urothelial carcinoma with clear cell change (3/6), clear cell meningioma (4/6) and ependymoma (2/3), haemangioblastoma (10/10), and clear cell hidradenoma (5/6). However, while strong and diffuse positivity for CA IX was observed in ccRCC, clear cell breast carcinoma, haemangioblastoma, and clear cell hidradenoma, the other cases showed predominantly focal positivity for CA IX. In particular, CA IX staining was often seen at the periphery of necrotic areas.

CONCLUSIONS

Our results indicate that strong and diffuse CA IX expression may be useful for differentiating ccRCC from several clear cell tumours, with the exception of clear cell breast carcinoma, haemangioblastoma, and clear cell hidradenoma.

Application of Immunohistochemistry in Thyroid Pathology

Context

Accurate classification of follicular-patterned thyroid lesions is not always an easy task on routine surgical hematoxylin-eosin–stained or cytologic fine-needle aspiration specimens. The diagnostic challenges are partially due to differential diagnostic criteria that are often subtle and subjective. In the past decades, tremendous advances have been made in molecular gene profiling of tumors and diagnostic immunohistochemistry, aiding in diagnostic accuracy and proper patient management.

Objective

To evaluate the diagnostic utility of the most commonly studied immunomarkers in the field of thyroid pathology by review of the literature, using the database of indexed articles in PubMed (US National Library of Medicine) from 1976–2013.

Data Sources

Literature review, authors' research data, and personal practice experience.

Conclusions

The appropriate use of immunohistochemistry by applying a panel of immunomarkers and using a standardized technical and interpretational method may complement the morphologic assessment and aid in the accurate classification of difficult thyroid lesions.

Carbonic anhydrase IX (CAIX) does not differentiate between benign and malignant mesothelium

OBJECTIVES

To examine carbonic anhydrase IX (CAIX), a marker of renal cell carcinoma that recently has been described in malignant effusions.

METHODS

Pleural and peritoneal fluids with the following diagnoses-reactive (n = 23), carcinoma (n = 17), and "suspicious for mesothelioma" (n = 4)-were immunostained for CAIX, calretinin, Ber-EP4, and MOC31. A tissue microarray of epithelioid (n = 27) and sarcomatoid (n = 8) mesotheliomas and three cases of benign mesothelium were also immunostained for CAIX.

RESULTS

Mesothelial cells in both reactive (18/23) and malignant effusions (18/21) were positive for CAIX (P > .05). In carcinomatous effusions, CAIX expression was restricted to the mesothelial cells. Agreement between CAIX and calretinin expression was present in 89% of cases. In tissues, CAIX was positive in 100% of benign and 91% of malignant mesothelium.

CONCLUSIONS

CAIX can be a useful ancillary marker for identifying mesothelial cells. There is no difference in CAIX expression between benign and malignant mesothelium. Caution should be exercised while evaluating for metastasis from renal cell carcinoma.

PAX8 is expressed in anaplastic thyroid carcinoma diagnosed by fine-needle aspiration: a study of three cases with histological correlates

OBJECTIVE

It is difficult to diagnose anaplastic thyroid carcinoma (ATC) in a fine-needle aspiration (FNA) sample because, given the loss of morphological and immunophenotypical follicular thyroid features, its cytology resembles that of other undifferentiated neoplasms. Recent studies have shown that immunostaining for paired box gene 8 (PAX8), a transcription factor expressed in normal thyroid, is effective for diagnosing ATCs on histology. The aim of this study was to evaluate whether PAX8 could be used to identify ATCs on cytology also.

DESIGN AND METHODS

We selected three PAX8-immunostained undifferentiated FNA samples previously diagnosed as suspected ATCs, whose cell block had been negative for the expression of TGB and thyroid transcription factor-1. Matched histological samples, available in two cases, were also processed for PAX8 immunohistochemistry.

RESULTS

All three FNA samples were PAX8 positive. Two samples that had an epithelioid pattern showed a diffuse, intense nuclear signal. The third sample, which had a spindle-cell pattern, showed less intense and more patchy staining. Matched histology yielded overlapping results.

CONCLUSIONS

PAX8 immunocytochemistry can help cytopathologists to diagnose ATCs.

Value of thyroid transcription factor-1 immunostaining in tumor diagnosis: a review and update

Thyroid transcription factor-1 (TTF-1) is a tissue-specific transcription factor that plays a critical role in the normal development of embryonic epithelial cells of the thyroid and lung. Because TTF-1 expression is highly restricted to epithelial tumors arising in these organs, it is, at present, one of the immunohistochemical markers most commonly used to assist in the differential diagnosis of carcinomas of the lung and thyroid. Recent studies, however, have reported that TTF-1 is not as specific for lung and thyroid carcinomas as was previously thought as it can be found to be expressed, although much less frequently, in some carcinomas arising in other organs, such as the ovaries, endometrium, colon, and breast, as well as in some tumors of the central nervous system. Even though this unexpected TTF-1 positivity has been reported more frequently with the recently available SPT24 anti-TTF-1 monoclonal antibody, it has also been shown to occur with the commonly used 8G7G3/1 clone, albeit in a lower percentage of cases. Despite these findings, TTF-1 remains a very useful immunohistochemical marker in diagnostic pathology.

PAX2 and PAX8 Expression in Primary and Metastatic Renal Tumors: A Comprehensive Comparison

Context.—The diagnosis of renal cell carcinoma (RCC) remains problematic, especially in the context of metastasis or small-needle biopsies. PAX2 and PAX8 transcription factors are known to be expressed by several histologic types of renal neoplasms.

Objective.—To evaluate the diagnostic utility of PAX2 and PAX8 relative to one another, which has not been studied.

Design.—Consecutive tissue sections from the archival samples of 243 primary and 99 metastatic renal neoplasms were submitted to PAX2 and PAX8 immunostain.

Results.—Within the primary neoplasms, PAX2 versus PAX8 expression was noted in 90 of 95 (95%) versus 92 of 95 (97%) for clear cell RCC, 29 of 38 (76%) versus 38 of 38 (100%) for papillary RCC, 14 of 25 (56%) versus 22 of 25 (88%) for chromophobe RCC, 3 of 7 (43%) versus 5 of 7 (71%) for collecting duct RCC, 6 of 8 (75%) versus 8 of 8 (100%) for acquired cystic kidney disease–related RCC, and 7 of 13 (54%) versus 11 of 13 (85%) for oncocytoma. Regardless of histologic subtype, PAX8 staining was noted in more cells and with more intense staining than PAX2. Within the metastatic RCCs, PAX8 expression was more frequently positive than PAX2 expression (88 of 99 cases; 89%; versus 75 of 99 cases; 76%).

Conclusions.—Both PAX2 and PAX8 are diagnostically useful markers for both primary and metastatic renal neoplasms of a large variety of histologic types. However, PAX8 appears to be more sensitive than PAX2 in both primary and metastatic settings. PAX8 can be included in any immunohistochemical panel for the diagnosis of primary renal neoplasms. Adding PAX2 should be optional, but this would gain limited further diagnostic yield. In a metastatic setting, both PAX8 and PAX2 can be included in a panel because a small subset of metastatic RCCs are stained only with PAX2.

Metastatic thyroid follicular carcinoma presenting as a primary renal tumor

Renal tumor metastasis from thyroid follicular carcinoma is very rare. Here, we present a 64-year-old woman with metastatic thyroid follicular carcinoma presenting as a primary renal tumor. The renal tumor was removed and revealed the origin of thyroid follicular carcinoma. Six months after the treatment of renal tumor, the patient was readmitted for the enlarged thyroid gland. The follicular carcinoma was revealed in the resected thyroid gland. The serum thyroglobulin level and thyroid function tests were consistently normal. Although with metastasis to the kidney, thyroid follicular carcinoma is thought to have a good prognosis.