Encapsulated anaplastic thyroid carcinoma transformed from follicular carcinoma: a case report

Coexisting well-differentiated and anaplastic thyroid carcinoma in the same primary resection specimen: immunophenotypic and genetic comparison of the two components in a consecutive series of 13 cases and a review of the literature

Anaplastic carcinoma (AC) is a rare but highly aggressive form of thyroid cancer. It mostly arises on a background of pre-existing well-differentiated cancer (WDC); however, whether it evolves directly from a WDC or originates as a second independent neoplasm is still to be defined. To obtain further insights into these mechanisms, we performed morphological, immunohistochemical, and next-generation sequencing analyses to compare AC and its associated WDC in a subset of 13 surgically resected specimens. Histologically, most WDC were of aggressive subtypes. Papillary carcinomas (8 cases; 62%) were tall cell (4/8), columnar (1/8), classic with hobnail features (1/8), classic and follicular variant in the remaining 2 cases; Hürthle cell and follicular carcinomas were present in 5 (38%) and in 1 (8%) patient, respectively. One patient harbored both a PTC, follicular variant, and a Hürthle cell carcinoma. We did not find any correlation between a histotype of WDC and a specific anaplastic growth pattern. Immunohistochemically, ACs retained pankeratin/PAX8 expression but with significantly lower levels than WDCs, and they tended to lose TTF1 expression, as can be expected within a dedifferentiation process. In addition, AC showed a more frequent expression of p63 and/or SMA, a mutated pattern of p53, and an abnormal expression of p16. Genetic analysis showed that the number of mutations was higher in AC than in the associated WDC, confirming a role of the progressive accumulation of genetic damage in this transition. We observed that mutations found in the WDCs were consistently identified in the anaplastic counterparts, further supporting the hypothesis of a developmental link.

NONINVASIVE ENCAPSULATED ANAPLASTIC THYROID CARCINOMA PROMISING AN EXCELLENT CLINICAL COURSE: A CASE REPORT AND REVIEW OF THE LITERATURE

Context

Noninvasive encapsulated anaplastic thyroid carcinomas (NE-ATCs) have been described in few case reports, and consistently associated with favorable outcome compared to the classical ATCs.

Objective

Our aim is to remark a rare histological finding in ATCs, encapsulation, which has been associated with a favorable outcome.

Design

We have documented a rare case of an NE-ATC with its clinical, pathological, and molecular features. We also provided a thorough discussion of all the encapsulated ATCs reported in the literature.

Subjects and Methods

A 50-year-old woman with an unremarkable medical history, who presented with a thyroid nodule, and diagnosed as "follicular lesion of undetermined significance" by fine needle aspiration biopsy. The patient was lost to follow-up for six years and revisited upon her neck disturbances and underwent total thyroidectomy.

Results

Sections of the right lobe revealed a grossly encapsulated nodular lesion, measuring 75x55x55 mm. Histologically, the tumor consisted of both carcinomatous and sarcomatous components supported by immunohistochemical stains. Necrosis and atypical mitotic figures were evident. Capsular and/or vascular invasion was not identified. There were no BRAF codon 600, KRAS, NRAS mutations and RET/PTC rearrangement. During three-month follow-up, the patient was free of disease without adjuvant therapy.

Conclusion

Encapsulated ATCs tend to follow a favorable clinical course and may deserve conservative treatment approaches.

Noninvasive anaplastic thyroid carcinoma: report of a case and literature review

Anaplastic thyroid carcinoma (ATC) is an uncommon thyroid malignancy. Noninvasive ATC is a rare, surgically resectable variant with only four reported cases. We report a case of an 81-year-old man who presented with a 3.1 cm right thyroid lobe mass that on fine-needle aspiration biopsy was diagnosed as an ATC. Preoperative imaging revealed an encapsulated thyroid tumor without evidence of invasion of surrounding structures and no locoregional and distant metastases. A total thyroidectomy was performed that by histologic and immunohistochemical evaluation was diagnostic for a noninvasive ATC. Given the diagnosis of noninvasive ATC, adjuvant therapy was not administered. At 14 months following diagnosis, the patient remains disease free based on positron emission tomography/computed tomography imaging. A review of the outcomes of similar cases reported in the literature, as well as observations from our case, suggest a favorable prognosis for patients with noninvasive ATC. Noninvasive ATC may represent a distinct subset of resectable ATCs with an improved prognosis. The recently published American Thyroid Association (ATA) Guidelines for Management of Patients with ATC do not include this specific form of ATC. We encourage other authors to report similar cases in order to determine whether noninvasive ATC should be considered as a separate disease entity from the traditional highly lethal form of ATC.

Aggressive variants of follicular cell derived thyroid carcinoma; the so called 'real thyroid carcinomas'

The pathological diagnoses and classification schemes for thyroid carcinoma have changed over the past 20 years and continue to do so. New entities have been described and molecular analyses have suggested better characterisation and grouping of certain tumours. Because some of the lesions have been named differently by different authors, clinicians and patients may be confused as to what a specific patient's lesion represents. In this review, we discuss the thyroid tumours of follicular origin which are clinically unusual but important to recognise as their behaviour may be aggressive, they may not respond to radioiodine treatment and they may cause significant mortality. This paper describes these important but rare lesions, their pathological features, important clinicopathological correlations, molecular correlates and prognostic implications.