Poorly differentiated thyroid carcinoma: a clinician's perspective

Management of Poorly Differentiated Thyroid Cancer and Differentiated High-Grade Thyroid Carcinoma

Thyroid carcinoma of follicular cell origin exists on a histopathologic and clinical spectrum. The authors focus on the category of tumors that fall between the very favorable well-differentiated thyroid carcinomas and the very unfavorable anaplastic thyroid carcinomas. These intermediately aggressive tumors include poorly differentiated thyroid carcinoma and the newly defined differentiated high-grade thyroid carcinoma. Both diagnoses require certain histopathologic requirements be met in order to accurately identify these tumors post-operatively. Management remains primarily surgical though adjunctive treatments such as molecular targeted therapies (eg, tyrosine kinase inhibitors) and differentiation therapy (to restore tumor response to radioactive iodine) are also becoming available.

[Thyroid carcinomas: the role of systemic therapies in internal medicine]

The molecular pathogenesis of thyroid carcinoma is well studied and of importance for the treatment of advanced stages. Differentiated, poorly differentiated and anaplastic carcinomas originate in the follicular cells, while medullary carcinomas derive from the C‑cells. The prognosis of differentiated thyroid carcinoma is generally very favourable after surgery and radioiodine therapy. Where tumours progress and lose the ability to enrich iodine, curative treatment is usually not possible. A strategy of watchful waiting is often appropriate. Activating mutations in BRAF or gene fusions of RET and NTRK provide opportunities for targeted therapies. These may be applied with the aim of restoring iodine uptake (redifferentiation). In the absence of molecular therapy targets, multityrosine kinase inhibitors (MKI) are the therapy of choice. If anaplastic thyroid carcinoma is suspected, rapid diagnostic workup including molecular pathology is warranted. Surgery where possible and radiochemotherapy are essential components of therapy. In the presence of a BRAF mutation, inhibition of BRAF and MEK is effective, even if it is not approved in Germany. Where molecular targets are lacking, combination therapy with the MKI lenvatinib and immune checkpoint inhibition is highly effective. Mutations in RET are present in the vast majority of cases of medullary thyroid carcinoma. In aggressive advanced disease, selective RET inhibition has recently been approved as first-line therapy and often leads to an objective response and long-lasting disease stabilisation. In summary, thyroid carcinomas are among the tumour entities for which molecularly targeted therapies can be used most frequently. The involvement of specialised centres is advisable.

A Comprehensive Review and Insights into the New Entity of Differentiated High-Grade Thyroid Carcinoma

Differentiated high-grade thyroid carcinoma (DHGTC) is a new subset within the spectrum of thyroid malignancies. This review aims to provide a comprehensive overview of DHGTC, focusing on its historical perspective, diagnosis, clinical characteristics, molecular profiles, management, and prognosis. DHGTC demonstrates an intermediate prognosis that falls between well-differentiated thyroid carcinoma and anaplastic thyroid carcinoma. Previously unenumerated, this entity is now recognized for its significant impact. Patients with DHGTC often present at an older age with advanced disease and exhibit aggressive clinical behavior. Molecularly, DHGTC shares similarities with other thyroid malignancies, harboring driver mutations such as BRAFV600E and RAS, along with additional late mutations. The unique behavior and histologic features of DHGTC underscore the necessity of precise classification for prognostication and treatment selection. This highlights the critical importance of accurate diagnosis and recognition by pathologists to enrich future research on this entity further.

Poorly differentiated thyroid carcinoma: molecular, clinico-pathological hallmarks and therapeutic perspectives

Poorly differentiated thyroid carcinoma (PDTC) is a rare and extremely aggressive tumor, accounting for about 2-15% of all thyroid cancer. PDTC has a distinct biological behavior compared to well-differentiated and anaplastic thyroid carcinoma and, in last years, it has been classified as a separate entity from both anatomopathological and clinical points of view. Nevertheless, there is still a lack of consensus among clinicians regarding inclusion criteria and definition of PDTC that affects its diagnosis and clinical management. Due to its rarity and difficulty in classification compared to other tumors, very few studies are available to date and series often include different histotypes in addition to PDTC. This review focuses on main studies concerning PDTC summarizing the evolution in the definition of its diagnosis criteria, clinicopathological features, management, and outcome. The data available confirm that the pathological evaluation and classification of PDTC are crucial and should therefore be standardized. Since the clinical presentation and prognosis of PDTC may vary widely depending on the different stage of the disease at diagnosis, the patient's management may differ in treatment and should be tailored to each patient. Finally, this review discusses advances in molecular insights of PDTC that, together with the implementation of both in vitro and in vivo models, will provide valuable insights into biological mechanisms of progression, metastasis, and invasion of this aggressive thyroid carcinoma. Further studies on larger, carefully selected series are needed to better assess the peculiar features of PDTC and to better define its management by focusing on the best diagnostic and therapeutic approaches.

Poorly differentiated thyroid carcinomas: conceptual controversy and clinical impact

Poorly differentiated thyroid carcinomas (PDTC) are rare diseases; nevertheless, they account for the majority of deaths from non-anaplastic follicular cell-derived thyroid carcinomas. Establishing the diagnosis and treatment of PDTC is challenging given the low incidence and the lack of standardization of diagnostic criteria. These limitations hamper the ability to compare therapeutic modalities and outcomes between recent and older studies. Recently, the 5th edition of the classification of endocrine tumors has been published, which includes changes in nomenclature and the addition of the disease entity of "differentiated high-grade follicular cell-derived carcinomas". On the other hand, the recently witnessed advances in molecular diagnostics have enriched therapeutic options and improved prognosis for patients. We herein review the various historical variations and evolution in the diagnostic criteria for PDTC. This systematic review attempts to clarify the evolution of the histological and molecular characteristics of this disease, its prognosis, as well as its treatment options.

Response to sorafenib in a locally advanced oncocytic cell carcinoma of the thyroid

We present the case of a female patient in her late 70s, diagnosed with widely invasive oncocytic cell carcinoma, with extrathyroidal extension, infiltration into the extrathyroidal muscle, involvement of the sternohyoid muscle and infiltration into the external muscle fibres of the oesophagus. Over the following year, metastases were documented in the lungs, bones and brain. Additionally, there was progression of the locally advanced lesion involving the airway and upper gastrointestinal tract. After considering iodine refractoriness, treatment with sorafenib was initiated. Notably, regression of the locoregional lesion at the cervical level was observed following treatment with the multikinase inhibitor.

A Misleading Case of NTRK-Rearranged Papillary Thyroid Carcinoma

Herein, we present a misleading case of advanced papillary thyroid carcinoma with lung, node, and pleural metastases, initially diagnosed as metastatic lung adenocarcinoma with papillary features, based on the histological and immunohistochemical analysis of a pleural biopsy. Between August 2019 and August 2020, the patient received 2 ineffective lines of systemic therapy, including a first line of chemotherapy with cisplatin and pemetrexed, and a second line of immunotherapy with atezolizumab. Comprehensive genomic profiling by next-generation sequencing on the archival pleural biopsy revealed an NTRK1-TMP3 fusion and comutation of the TERT promoter, commonly found in papillary thyroid carcinoma. After palliative partial thyroidectomy that confirmed the diagnosis of papillary thyroid carcinoma, in February 2021, the patient was enrolled in the STARTRK-2 GO40782 basket trial and received entrectinib, an oral pan-TRK inhibitor specifically targeting NTRK-rearranged tumors. After initially experiencing drug-related grade 2 anorexia, dysgeusia, and neurotoxicity and grade 3 asthenia, the dose was reduced, and an excellent and durable objective response was observed.

Characterization of the genomic alterations in poorly differentiated thyroid cancer

Poorly differentiated thyroid carcinoma (PDTC) is a subtype of thyroid cancer that has a high rate of metastasis or recurrence and a relatively poor prognosis. However, there are few studies that have been conducted on PDTC at the whole protein-coding gene scale. Here, we performed genomic profiling of 15 patients with PDTC originated from follicular thyroid carcinoma using whole exome sequencing and also performed gene functional enrichment analysis of differentially expressed genes (DEGs) for three patients. Further, we investigated genetic variants associated with PDTC progression and the characteristics of clinical pathology. We revealed somatic genomic alterations in the RAF1, MAP2K2, and AKT2 genes that were not reported in previous studies. We confirmed frequent occurrences in the RAS gene in patients with PDTC; the genetic alterations were associated with the RAS-RAF-MEK-ERK/JNK, PI3K-AKT-mTOR signaling pathways, and the cell cycle. DEG analysis showed that immune response was lower in cancer tissues than in normal tissues. Through the association analysis of somatic mutations and the characteristics of clinical pathology from patients with PDTC, the somatic mutations of ABCA12, CLIP1, and ATP13A3 were significantly associated with a vascular invasion phenotype. By providing molecular genetic insight on PDTC, this study may contribute to the discovery of novel therapeutic target candidates.

Calcaneus metastasis: a rare presentation of poorly differentiated thyroid cancer

Summary

A 60-year-old woman presented to our clinic with an acute onset 3 months history of right ankle pain. The patient had a history of poorly differentiated thyroid cancer, which was treated with total thyroidectomy, left lateral neck dissection levels II-V and central neck dissection levels VI-VII followed by postoperative I-131 radioactive iodine (131I) ablation therapy 3.7 GBq 6 months ago. The post-131I WBS showed residual iodine-avid thyroid tissue with no other iodine-avid disease or metastasis. SPECT/CT of the neck and chest showed nonavid bilateral pulmonary nodules, discrete nodal masses in mediastinum and nonavid bone lesions. FDG-PET CT scan showed FDG-avid mediastinal lymph nodes (LN), innumerable non-FDG-avid subcentimetric pulmonary nodules and few FDG-avid lytic lesions in the skeleton. X-ray and MRI of the right ankle showed a well-marginated lytic lesion in the posterior body of calcaneus and 5 × 6 cm soft tissue mass lesion, respectively. The histopathology of the calcaneus mass confirmed a positive immunostaining for thyroid origin which includes thyroglobulin and TTF-1 with PAX-8. Endobronchial mediastinal and bronchial LN biopsy confirmed thyroid cancer metastasis. Gene mutation showed HRAS and GNA13 with a high tumor mutational burden. We describe a rare case of poorly differentiated thyroid cancer in a patient who presented with right ankle pain; we confirmed the cause to be a calcaneus metastasis from the thyroid cancer, with calcaneus being an extremely rare site for bone metastases. Gene mutations points toward treatment with immune checkpoint inhibitors.

Learning points

Poorly differentiated thyroid carcinoma (PDTC) usually metastasizes to lung and bone but can rarely occur in the calcaneus. Patients with distant metastases have significantly worse long-term prognosis. Radiotherapy is effective in reducing the metastatic pains as well as reducing the size of the metastasis. PAX-8 staining can be used to differentiate thyroid carcinomas from lung adenocarcinomas. The importance of searching for gene mutations to decide the treatment of PDTC.

Revisiting the cytomorphological features of poorly differentiated thyroid carcinoma: a comparative analysis with indeterminate thyroid fine-needle aspiration samples

INTRODUCTION

Poorly differentiated thyroid carcinoma (PDTC) is an uncommon high-grade carcinoma of follicular cell origin that is usually overlooked on preoperative fine-needle aspiration (FNA) due to its rarity and cytomorphological overlap with follicular-patterned neoplasms. Definitive diagnosis of PDTC usually requires histologic examination of the resected thyroid tumor. Herein, we describe the cytological and architectural findings of histologically confirmed PDTC cases.

MATERIALS AND METHODS

A search for all thyroid FNAs with a corresponding surgical diagnosis of PDTC was performed. Surgical diagnoses were reviewed and confirmed using the Turin criteria. In addition, the control group consisted of indeterminate thyroid nodules (FLUS [follicular lesion of undetermined significance] and FN [follicular neoplasm]) that were either benign or well-differentiated thyroid tumors on resection. The PDTC and control groups were both subjected to cytological assessment using specific cytological and architectural parameters, which included cellularity, growth pattern, mitoses, necrosis, chromatin change, discohesion, and anisonucleosis.

RESULTS

A total of 36 thyroid FNAs were included in the study. This consisted of 12 histologically confirmed PDTC FNAs and 24 indeterminate thyroid FNAs (FLUS and FN, 12 each). The most frequent findings among PDTC groups were hypercellularity (75%), trabecular/insular growth pattern (58%), branching capillaries (67%), and cellular discohesion (92%). Necrosis (25%), ≥3 mitoses (50%), and anisonucleaosis (42%) were less frequently observed. A peculiar finding was the presence of adenoid cystic carcinoma-like globules in 50% of PDTC cases. Certain findings such as colloid, necrosis, mitoses, and cellular discohesion were helpful in differentiating the two groups.

CONCLUSIONS

Thyroid fine-needle aspiration remains an essential diagnostic/triage tool for most thyroid nodules/tumors. PDTC can be diagnosed or at least suspected preoperatively based on the demonstration of certain architectural and cytological alterations. Although mitoses and necroses are not always readily identified, an elevated Ki-67 labeling expression could provide additional clues to the diagnosis in some cases.

Cut-off Value for Thyroglobulin Washout Concentration in the Detection of Cervical Lymph Node Metastases in Patients after Thyroidectomy Due to Differentiated Thyroid Cancer

The aim of this study was to establish the cut-off value for the thyroglobulin (Tg) concentration in washout fluid from fine needle aspiration biopsy (FNA-Tg) in the detection of cervical lymph node metastases of differentiated thyroid cancer (DTC). We evaluated the validity and clinical utility of fine needle aspiration biopsy cytology (FNAB-C), FNA-Tg, and the combined method in detecting DTC recurrences. The study included 82 patients after the total thyroidectomy and elective and, in some cases, also selective cervical lymphadenectomy. The majority of patients also underwent subsequent 131I ablative therapy. The patients presented with 1-6 enlarged and/or ultrasonographically suspicious cervical lymph nodes. One to four aspirates of each lymph node were taken, with a total of 297 samples. An FNA-Tg of 4.34 ng/mL was established as the cut-off value for detecting cervical lymph node DTC metastases for the IRMA Brahms DYNO test, Tg-S. FNAB-C is highly specific (91-99%) but not sensitive enough (53-69%) to be used as a standalone method in the detection of cervical lymph node metastases. FNA-Tg is more sensitive (91%), but caution should be taken when selecting patients for surgery with an FNA-Tg higher than the established cut-off value but lower than the serum Tg concentration. To select patients for lymphadenectomy, we recommend using the combined method (FNAB-C and FNA-Tg) with a sensitivity of 96% and specificity of up to 97%. More than one sample should be taken with each fine needle aspiration biopsy (FNAB) to obtain a representative set of samples.

Expression of pY397-FAK and Its miR Regulators Drive Dedifferentiation in the Thyroid Neoplasia Spectrum

Thyroid carcinomas are growing malignancies worldwide. They encompass several diagnostic categories with varying degrees of dedifferentiation. Focal adhesion kinase is involved in cellular communication and locomotion. It is regulated on a posttranscriptional level by miR-7, miR-135a, and miR-138 and on a posttranslational level by autophosphorylation at Y397 (pY397-FAK). We related regulators of FAK with histologic dedifferentiation, clinicopathological factors, and differential diagnosis in the thyroid neoplasia spectrum. We classified 82 cases into 5 groups with increasing aggressiveness: healthy tissue, follicular and classical variants of papillary thyroid carcinoma (PTC), dedifferentiated PTC, and anaplastic carcinoma. MiRs were analyzed by RT-qPCR. Protein expression of pY397-FAK was analyzed by immunohistochemistry (separately in the membrane, cytoplasm, and nuclear compartment) and Western blot. All three miRs were upregulated in healthy tissue compared to malignant, while pY397-FAK was downregulated. MiRs and pY397-FAK were not mutually correlated. MiR-135a-5p was decreasing while membranous and cytoplasmic pY397-FAK increased with dedifferentiation. Neither miR correlated with clinicopathological factors. MiR-135a-5p, miR-138-5p, and membranous and cytoplasmic pY397-FAK discriminated the follicular from the classical variant of PTC. Disturbances of FAK regulation on different levels contribute to neoplastic dedifferentiation. pY397-FAK exerts its oncogenic role in the membrane and cytoplasm. Diagnostically, miRs-135a-5p, miR-138-5p, and membranous and cytoplasmic pY397-FAK differentiated between classical and follicular PTC.

Outcomes of lenvatinib therapy in poorly differentiated thyroid carcinoma

Background and objective

Lenvatinib showed promising results in a subgroup of patients with poorly differentiated thyroid carcinoma (PDTC) in the SELECT trial. Our aim was to report the effectiveness and tolerability of lenvatinib in our series of PDTC patients.

Methods

Medical records of eight consecutive patients with PDTC treated with lenvatinib in a single center between January 2019 and October 2022 were retrospectively reviewed. Inclusion criteria were PDTC diagnosis based on Turin criteria and evidence of disease progression in the previous 6 months.

Results

Eight PDTC patients received an average dose of lenvatinib of 18.1 mg for a median duration of treatment of 10.3 months. The baseline Eastern Cooperative Oncology Group performance status was ≥2 in 50% of patients. Two patients had unresectable primary tumor. Seven patients showed extrathyroidal disease, particularly mediastinal lymph nodes (85.7%), lung (71.4%), and bone (71.4%). The disease control rate was 100%, with partial response and stable disease in 12.5 and 87.5%, respectively. The median time to best overall response was 3 months, and the median duration of response was 7.5 months. Median progression-free survival was 12 months and median overall survival was not reached. At 6, 12, and 18 months, overall survival was 87.5, 71.4, and 57.1%, respectively. All patients experienced drug-related adverse effects (AEs). Four (50%) had dose reductions and two (25%) had temporary treatment interruptions. Lenvatinib was stopped in two patients due to grade ≥3 AEs.

Conclusion

Lenvatinib is an effective treatment for real-world PDTC patients. Adequate management of comorbidities and AEs increases treatment tolerability and minimizes dose reductions.

Diagnosis and Treatment of Acute Pleural Effusion following Radioiodine Remnant Ablation Post Lobectomy for Thyroid Cancer

Radioiodine remnant ablation (RRA) was previously demonstrated to be a safe and effective alternative to completion thyroidectomy for patients with differentiated thyroid cancer (DTC). However, its side effects have not been fully investigated, particularly in patients with lobectomy. We reported a young euthyroidal female who underwent RRA post lobectomy and lymph node dissection for papillary thyroid cancer, whose post-ablation ¹³¹I-whole-body scan accidentally showed diffuse radioiodine distribution on chest-mimicking pulmonary metastases. Immediately-added single-photon emission computed tomography/computed tomography (SPECT/CT), nevertheless, revealed a ¹³¹I-accumulating swollen left thyroid lobe and emerging pleural effusion, which relieved after short-term treatment with prednisone. In summary, acute pleural effusion ascribed to RRA-induced thoracic duct compression was reported for the first time. ¹³¹I-lobectomy-induced pleural effusion could be precisely diagnosed by SPECT/CT and efficiently manipulated via treating radiation thyroiditis with the short-term administration of corticosteroid.