Occult carcinoma of the thyroid gland

Adverse Histological Features of Differentiated Thyroid Cancer Are Commonly Found in Autopsy Studies: Implications for Treatment Guidelines

Background: While the popularity of lobectomy for differentiated thyroid cancer (DTC) has increased since the 2015 ATA (American Thyroid Association) guidelines, recent studies reported that adverse histological features (minimal extrathyroidal extension [mETE], multifocality, vascular invasion, and lymph node [LN] metastases) may be found in 30-60% of lobectomy specimens, questioning the validity of this approach. Aim: To assess the prevalence adverse histological features in occult DTC detected in autopsy studies. Methods: Meta-analysis of autopsy studies of the thyroid in subjects without known history of thyroid cancer. Results: Twenty-nine studies including 8750 subjects fulfilled the inclusion criteria, with incidentally discovered DTC in 740 autopsies (8.5%). Age was reported in 17 studies, with a median age of 61 years (range 41-68 years). Multifocality was reported in 27 studies with a calculated event rate of 28.2% ([CI 23.1-33.8], I² = 46.3%), with bilateral involvement in 18% [CI 12.6-25.1]. mETE was reported in 5 studies, with an event rate of 24.5% ([CI 9.3-50.7], I² = 88.5%), and the presence of LN metastases were reported in 13 studies with an event rate of 11% ([CI 6.1-19.1], I² = 69.5%). Vascular invasion was reported in seven studies with an event rate of 16% ([CI 4-47], I² = 86.8%). Of 25 studies with whole body autopsies (722 subjects), 3 cases of distant metastases were reported, of which 2 had fatal metastatic disease (where thyroid origin was not diagnosed before death), and 1 had occult disease. Conclusions: Adverse histological features including mETE, LN metastases, multifocality, and vascular invasion are common in occult DTC. When minimal in size, these adverse histological features do not seem to be markers of aggressive disease and may not be an indication for completion thyroidectomy or radioiodine therapy.

Prevalence of Differentiated Thyroid Cancer in Autopsy Studies Over Six Decades: A Meta-Analysis

Purpose

Differentiated thyroid cancer (DTC) incidence has been reported to have increased three- to 15-fold in the past few decades. It is unclear whether this represents overdiagnosis or a true increase in incidence. Therefore, the current study aimed to estimate the prevalence of incidental DTC in published autopsy series and determine whether this prevalence has been increasing over time.

Materials and Methods

PubMed, Embase, and Web of Science were searched from inception to December 2015 for relevant studies. Two authors searched for all autopsy studies that had included patients with no known history of thyroid pathology and reported the prevalence of incidental DTC (iDTC). Two authors independently extracted the data, and discrepancies were resolved by another author. The pooled prevalence of iDTC was assessed using a fixed-effects meta-analysis model with robust error variance. The time effect was studied using an inverse-variance weighted logit-linear regression model with robust error variance and a time variable.

Results

Thirty-five studies, conducted between 1949 and 2007, met the inclusion criteria and contributed 42 data sets and 12,834 autopsies. The prevalence of iDTC among the partial and whole examination subgroups was 4.1% (95% CI, 3.0% to 5.4%) and 11.2% (95% CI, 6.7% to 16.1%), respectively. Once the intensiveness of thyroid examination was accounted for in the regression model, the prevalence odds ratio stabilized from 1970 onward, and no time effect was observed.

Conclusion

The current study confirms that iDTC is common, but the observed increasing incidence is not mirrored by prevalence within autopsy studies and, therefore, is unlikely to reflect a true population-level increase in tumorigenesis. This strongly suggests that the current increasing incidence of iDTC most likely reflects diagnostic detection increasing over time.

Autopsy Findings in Clinically Normal Thyroids

Thyroid glands obtained from 120 consecutive autopsies performed on patients who died from different causes, other than thyroid diseases, were systematically examined by light microscopy. There were 84 males and 36 females; their ages ranged from 1 day to 100 years. Histopathological findings were noted mainly in patients older than 48 years of age. In all cases thyroid lesions were incidental findings and included nodular goiter (26%), thyroiditis (9%), follicular adenomas (7%), papillary microcarci nomas (6%), follicular carcinoma (0.8%), and hemangioma (0.8%). A number of other morphologic changes of importance to surgical pathologists were also evaluated such as the presence of solid cell nests, intrathyroidal ectopic tissues, fibrosis, fat cell infiltration, and vascular changes. Int J Surg Pathol 1 (I): 25-32, 1993

Iodine intake as a risk factor for thyroid cancer: a comprehensive review of animal and human studies

Thyroid cancer (TC) is the most common endocrine malignancy and in most countries, incidence rates are increasing. Although differences in population iodine intake are a determinant of benign thyroid disorders, the role of iodine intake in TC remains uncertain. We review the evidence linking iodine intake and TC from animal studies, ecological studies of iodine intake and differentiated and undifferentiated TC, iodine intake and mortality from TC and occult TC at autopsy, as well as the case–control and cohort studies of TC and intake of seafood and milk products. We perform a new meta-analysis of pooled measures of effect from case–control studies of total iodine intake and TC. Finally, we examine the post-Chernobyl studies linking iodine status and risk of TC after radiation exposure. The available evidence suggests iodine deficiency is a risk factor for TC, particularly for follicular TC and possibly, for anaplastic TC. This conclusion is based on: a) consistent data showing an increase in TC (mainly follicular) in iodine deficient animals; b) a plausible mechanism (chronic TSH stimulation induced by iodine deficiency); c) consistent data from before and after studies of iodine prophylaxis showing a decrease in follicular TC and anaplastic TC; d) the indirect association between changes in iodine intake and TC mortality in the decade from 2000 to 2010; e) the autopsy studies of occult TC showing higher microcarcinoma rates with lower iodine intakes; and f) the case control studies suggesting lower risk of TC with higher total iodine intakes.

Papillary thyroid microcarcinomas are different from latent papillary thyroid carcinomas at autopsy

The aim of this study was to review the literature of latent papillary thyroid carcinomas (PTCs) discovered at autopsy and describe the available pathologic and demographic differences from a group of papillary thyroid microcarcinomas (PTMCs) the reported in a previous publication. We searched the PubMed for published articles describing latent thyroid carcinomas detected at autopsy. Meta-analysis was performed to identify differences between the clinicopathologic features of PTMCs analyzed previously in our institution (Group I) and those of latent PTCs described in autopsy studies (Group II). We identified 1,355 patients with PTMC (Group I) and 989 with latent PTCs (Group II). Mean patient age was 47.3 yr in Group I and 64.5 yr in Group II. The male:female ratio was 1:10.9 in Group I and 1:1 in Group II. Most PTMCs (67.6%) were larger than 0.5 cm in size, whereas most latent PTCs were <1-3 mm in diameter. The rates of multifocality were 24.7% in Group I and 30.5% in Group II, and the rates of cervical lymph node metastasis were 33.4% in Group I and 10.0% in Group II. Currently available data indicated that clinically evident PTMCs differ from latent PTCs detected at autopsy. Therefore, these two entities should be regarded as different.

Thyroid microcarcinoma

Nowadays the most commonly occurring differentiated thyroid cancer in many countries is a microcarcinoma in patients older than 45 years, incidentally found during neck ultrasound. In view of their low morbidity and mortality, the crucial point is how to manage such microcarcinomas. Recently published European and American guidelines aim to minimize the diagnostic and therapeutic procedures without affecting the diagnostic accuracy and the therapeutic effectiveness, keeping in mind that we are dealing with patients who have a normal life expectancy and to whom we have to guarantee an excellent quality of life. The present review will summarize the clinical and pathological features of thyroid microcarcinoma, including its definition, prevalence, presentation, pathology, genetic, clinical impact and will try to derive from them a rationale for therapeutic and diagnostic intervention.

Thyroid microcarcinoma

Nowadays the most commonly occurring differentiated thyroid cancer in many countries is a microcarcinoma in patients older than 45 years, incidentally found during neck ultrasound. In view of their low morbidity and mortality, the crucial point is how to manage such microcarcinomas. Recently published European and American guidelines aim to minimize the diagnostic and therapeutic procedures without affecting the diagnostic accuracy and the therapeutic effectiveness, keeping in mind that we are dealing with patients who have a normal life expectancy and to whom we have to guarantee an excellent quality of life. The present review will summarize the clinical and pathological features of thyroid microcarcinoma, including its definition, prevalence, presentation, pathology, genetic, clinical impact and will try to derive from them a rationale for therapeutic and diagnostic intervention.

Thyroid cancer, thyroiditis and dietary iodine: a review based on the Salta, Argentina model

Factors that should be considered when studying the effect of dietary iodine in the development of thyroid cancer include pathological criteria, diagnostic techniques, screening programs, radioactive fallout, and standard of medical care in the studied population. In most surveys, papillary carcinoma forms the largest group of thyroid malignancies, both before and after iodine prophylaxis where an increase in the papillary:follicular carcinoma ratio is also noted. Undifferentiated carcinomas decrease after salt prophylaxis. In Salta, Argentina, the increasing incidence of clinically significant papillary thyroid cancer and the decrease of undifferentiated carcinoma after iodine prophylaxis are probably due to better access to health centers and consequent earlier detection of differentiated precursor tumors. Autoimmune focal and diffuse or Hashimoto's thyroiditis are linked to dietary iodine. Pathological studies made in different regions indicate that these types of thyroiditis occur more frequently in areas of iodine sufficiency than in areas of iodine deficiency, and increase after iodine prophylaxis both in non-goitrous and iodine-deficient areas like Salta, Argentina. An increase of lymphocytic thyroiditis could be linked to an increased incidence of primary thyroid lymphoma, and thyroiditis is more commonly associated with papillary carcinoma than with other types of thyroid follicular or C-cell derived carcinomas regardless of iodine intake.

Clinical features and therapeutic implication of papillary thyroid microcarcinoma

Papillary thyroid microcarcinomas (PTMs) are small tumors (< or =1 cm of diameter) that belong to the well-differentiated low-risk carcinomas of the thyroid, which are characterized by benign behavior, probably of little clinical significance, and do not affect patients' survival. They are found in otherwise normal thyroids or in multinodular goiters with a clinical frequency varying substantially according to different series. Sometimes, PTM may be associated with lymph node metastases at presentation and/or locoregional recurrences during follow-up. Distant metastases are extremely rare, but have been reported. Although deaths related to PTM are almost unknown, PTM raises therapeutic implications. This review addresses the issue of definition, treatment, and follow-up of PTM.

Medullary thyroid microcarcinoma: a clinicopathologic retrospective study of 38 patients with no prior familial disease

Thirty-eight patients (25 women, 13 men; mean age, 57.8 [32 to 91]) showing one or more medullary thyroid microcarcinomas (ie, < 1 cm), with no prior MEN II or medullary thyroid carcinoma history in their family, were reviewed. Follow-up was available for 29 patients (mean, 53.6 months [1 to 147]). 21 patients (72.4%) are alive and free of disease, four patients (13.8%) died during follow-up without disease, 2 patients are alive with disease (local recurrence and persistent hypercalcitoninemia) after 80 and 99 months, respectively, and 2 patients died of disease after 24 and 46 months. Most tumors were incidental pathological findings (19 of 38) or were discovered by systematic blood calcitonin measurement for a nodular thyroid disease (15 of 38). Only the four patients who had an unfavorable outcome were symptomatic cases (palpable micro-MTC, diarrhea, cervical lymph node metastasis and pulmonary metastatic disease). The two patients with metastatic disease at diagnosis died during follow-up. In univariate analysis, a symptomatic medullary thyroid carcinoma was a strong predictor of an unfavourable outcome (p < .00008), as were the preoperative calcitonin level (P = .007) and an elevated postoperative calcitonin level (P = .004). Among 30 histopathological criteria, only the presence of amyloid correlated with an unfavorable outcome (P = .018).

Papillary microcarcinoma of the thyroid

Papillary microcarcinoma of the thyroid has been often detected by aspiration biopsy cytology performed with ultrasonographic guidance. Autopsy studies also have often revealed small thyroid carcinomas, and it was concluded that most small thyroid carcinomas should not be regarded as a clinical matter. In this study, 112 patients with papillary microcarcinoma 10 mm or less in size treated between 1992 and 1995 were analyzed. There were 104 females and 8 males, with a mean age of 46.0 years. Diagnosis of papillary carcinoma was made preoperatively in 100 of these patients (89.3%), and 77 patients underwent aspiration biopsy cytology under ultrasound guidance. Seventy of these patients underwent modified neck dissection, and 63.8% of these patients had lymph node metastases. The number of lymph node metastasis increased as primary tumor size increased. There was no clear border or clinical differences between primary tumors 10 mm or less and tumors more than 10 mm. One patient had lymph node recurrence after surgery and another patient had recurrent nerve palsy at the first visit. Based on these findings, papillary microcarcinoma should be treated surgically.

Papillary microcarcinoma of the thyroid gland

Papillary microcarcinomas are a specific subgroup of papillary thyroid cancer. They have the same histological features as papillary thyroid cancer but are 1.0 cm or less in diameter. These tumours are a common incidental finding at autopsy and in thyroid glands excised for other pathology. This tumour can metastasize to regional lymph nodes but its ability to cause significant morbidity and mortality has been questioned. As papillary microcarcinomas can represent up to 30 per cent of all papillary cancers seen in a thyroid surgeon's practice, they are an important group. The aim of this review article is to outline the natural history of papillary microcarcinoma and to offer therapeutic management strategies.

Nonpalpable occult and metastatic papillary thyroid carcinoma

The results of palpation, ultrasound, and detailed pathology were compared in 50 patients undergoing total thyroidectomy. Of the 211 nodules recognized by pathology, palpation detected 24% and ultrasound detected 43%. There were 14 patients with palpable papillary carcinomas, and 12 of these 14 had metastatic foci in other portions of the gland. Metastatic foci would have been left in 10 patients if only a lobectomy had been performed and would have been left in 6 patients if only a subtotal thyroidectomy (as defined in this report) had been performed. Of the 33 patients with benign palpable nodules, 5 had occult papillary carcinomas. In 2 of those 5 patients, the occult carcinomas would not have been removed if a less-than-total thyroidectomy had been performed. The significance of these occult and metastatic papillary carcinomas is discussed.

Latent thyroid carcinoma in Iceland at autopsy

The annual incidence rate of thyroid carcinoma in Iceland is high, 4.4 pr. 100,000 men, and 11.7 pr. 100,000 women, as published by the Icelandic Cancer Registry for the period 1955-1984. This rate is more than twice that in the other Nordic countries and one of the highest incidence rates reported anywhere. This led us to investigate the prevalence rate of latent thyroid carcinoma in Iceland. We serially sectioned and examined thyroid glands from 201 consecutive forensic autopsies. Altogether, sixteen carcinomas were identified in fourteen glands: fourteen papillary, one follicular and one medullary carcinoma. We conclude that the prevalence rate of latent thyroid carcinoma in each sex does not follow the frequency distribution of clinical disease, being 7.5% in males and 5.1% in females. Comparisons between populations show the same lack of consistency. Further, most, but not all, latent carcinomas of the thyroid gland are of the papillary type. These findings suggest that promoting factors might be of particular importance where incidence and mortality rates are high, but further research is needed into the role of host resistance.

New subgrouping of small thyroid carcinomas

Clinicopathologic findings on small thyroid carcinomas measuring 10 mm or less in diameter were analyzed in 78 thyroidectomied cases. The authors divided small thyroid tumors into two subgroups according to diameter: 0 less than or equal to 5 mm (classified as minute carcinoma) and 5 less than 0 less than or equal to 10 mm (classified as tiny carcinomas). Characteristics including sex, age, histologic type, extrathyroid invasion, and lymph node metastasis were examined in each subgroup. In patients with minute carcinoma, very few incidences of extrathyroid invasion and lymph node metastasis were found. However, these involvements, especially lymph node metastasis, were found more frequently in patients with tiny carcinoma. The incidence of cervical lymph node metastasis was 13% in minute carcinoma and 59% in tiny carcinoma. (P less than 0.01). These findings suggest the need for more careful observation and treatment of tiny carcinomas, especially with respect to lymph node metastasis. In accordance with World Health Organization (WHO) classification, the histologic types of thyroid carcinoma were classified into papillary and follicular carcinomas. The papillary carcinoma and follicular carcinoma ratios were compared between the two subgroups. The discovery rate of follicular carcinoma was significantly higher in minute carcinoma than in tiny carcinoma (P less than 0.005). This suggests that the papillary carcinoma/follicular carcinoma ratio (p/f) increases as the size of the carcinoma increases, and that follicular carcinoma is the "seed," or initial form, of thyroid cancer. The female-male ratio in small thyroid cancer suggests that there is no sex difference in carcinogenesis but that there is more probability for cancer development in the thyroid in women.

Demonstration of nodules in the normal thyroid by echography

An ultrasound examination was performed of the normal thyroid in 300 patients (164 males and 136 females). Small echoic nodules were demonstrated in 19% of the patients and fluid-filled masses in 6%. Echoic nodules occurred frequently (greater than 40%) in the seventh decade. 71% of the nodules were situated in the right lobe.