Unilateral malignant struma ovarii in a case of bilateral ovarian teratoma with raised CA-125 level: a rare case with treatment dilemmas

Struma ovarii are specialized form of mature ovarian teratoma comprised predominantly of thyroid tissue (>50%). Most of the struma ovarii are benign; rarely can they undergo malignant transformation. Elevated CA-125 levels with benign struma ovarii have been seen in only 5 cases in literature. The association of malignant struma ovarii and high CA-125 levels with pseudo-Meig syndrome has been reported in only 2 cases in English literature. We describe a case of a 46-year-old multigravida who presented with an abdominal mass and raised CA-125 levels. Radiological investigations revealed bilateral cystic adnexal masses with ossified elements on left side suggesting a teratoma. Intraoperative frozen section and final pathology revealed bilateral teratoma with follicular variant of papillary thyroid carcinoma arising in the left ovary. To the best of our knowledge, this is the first case of malignant struma ovarii in combination with bilateral teratoma. The dilemmas related to preoperative diagnoses with elevated CA-125 levels, mimicking an epithelial ovarian neoplasm; intraoperative frozen section consultation; management and follow-up issues in this rare malignancy are discussed.     

BRAF T1799A mutation occurring in a case of malignant struma ovarii

Struma ovarii is an extremely rare tumor that occasionally undergoes malignant transformation. Because struma ovarii is composed of thyroid tissue, it is conceivable that the pathogenetic events involved in thyroid follicular transformation may take place also in struma ovarii. The authors describe a case of a classical variant of papillary thyroid carcinoma arising in a struma ovarii of a 22-year-old female. The tumor was heterozygous for BRAF T1799A mutation. No ret/ PTC-1 or ret/PTC-3 rearrangements were detected. This finding would suggest that malignant struma ovarii is similar histologically and genetically to primary papillary thyroid carcinoma.     

Genetic alterations involved in the transition from well-differentiated to poorly differentiated and anaplastic thyroid carcinomas

Recent molecular studies have provided new insights into thyroid carcinogenesis. In thyroid papillary carcinomas at least three initiating events may occur, which are point mutations in the BRAF and RAS genes and RET/PTC rearrangements. Tumors harboring mutant BRAF and RAS are prone to progression to poorly differentiated and anaplastic carcinoma, but most likely require additional mutations to trigger this process. In thyroid follicular carcinomas, two known initiating events are RAS mutations and PAX8-PPARγ rearrangements, and RAS predisposes to dedifferentiation of follicular carcinomas. p53 and β-catenin mutations, found with increasing incidence in poorly differentiated and anaplastic carcinomas but not in well-differentiated tumors, may serve as a direct molecular trigger of tumor dedifferentiation. Additional evidence for progression from a preexisting well-differentiated carcinoma to poorly differentiated and anaplastic carcinoma comes from the studies of loss of heterozygosity and comparative genomic hybridization. Molecular studies, although limited by the lack of uniform histologic criteria for poorly differentiated carcinomas, revealed no genetic mutations or chromosomal abnormalities that are unique for poorly differentiated carcinoma and not present in well-differentiated or anaplastic carcinomas. This suggests that poorly differentiated carcinoma, as a group, represents a distinct step in the evolution from well-differentiated to anaplastic thyroid carcinoma, rather than an entirely separate type of thyroid malignancy.     

The contribution of molecular pathology to the classification of thyroid tumors

Significant molecular advances have been undertaken for the past two decades in the field of thyroid follicular neoplasms, including a detailed genomic profile of papillary thyroid carcinoma (PTC) by The Cancer Genome Atlas (TCGA) project. These molecular discoveries led to a better understanding of the pathogenesis of thyroid neoplasms and resulted in reclassification of certain types of thyroid tumors. This review discusses how, 1) the molecular profiles of follicular-patterned lesions led to the reclassification of the follicular variant of PTC into non-invasive follicular thyroid neoplasm with papillary like nuclei, 2) the genotyping of Hürthle cell neoplasm provided the rationale to classify these tumors independently from follicular adenomas and carcinomas, and 3) BRAF and RAS molecular signatures have the potential of subclassifying PTC and poorly differentiated thyroid carcinoma into clinically relevant molecular subtypes.     

Alterations of the BRAF gene in thyroid tumors

BRAF belongs to the RAF family of protein kinases that are important components of the MAPK signaling pathway mediating cell growth, differentiation and survival. Activating point mutation of the BRAF gene resulting in V600E (previously designated as V599E) is a common event in thyroid papillary carcinoma, being found in approx 40% of this tumor. It has strong association with classical papillary carcinoma and tall cell and possibly Warthin-like variants. This mutation also occurs in thyroid poorly differentiated and anaplastic carcinomas, usually those containing areas of papillary carcinoma. Alterations in the BRAF gene do not overlap with RAS mutations and RET/PTC rearrangement, indicating that activation of one of the effectors of the MAPK pathway is sufficient for papillary thyroid carcinogenesis. Recently, another mechanism of BRAF activation has been identified, which involves chromosome 7q inversion that results in the AKAP9-BRAF fusion. It is rare in sporadic papillary carcinomas and is more common in tumors associated with radiation exposure. Yet another mechanism of BRAF activation may involve copy number gain, which is seen in a significant portion of thyroid follicular tumors of both conventional and oncocytic (Hürthle cell) types.     

Encapsulated Malignant Follicular Cell-Derived Thyroid Tumors

Encapsulated malignant follicular cell-derived thyroid tumors are subject to considerable controversies. This group includes encapsulated follicular variant of papillary carcinoma (FVPTC) and encapsulated (so-called minimally invasive) follicular carcinoma (EFC). FVPTC usually presents as an encapsulated tumor and less commonly as a partially/nonencapsulated infiltrative neoplasm. The encapsulated form rarely metastasizes to lymph node, whereas infiltrative tumors often harbor nodal metastases. Encapsulated FVPTC have a molecular profile very close to follicular adenomas/carcinomas (high rate of RAS and absence of BRAF mutations). Infiltrative follicular variant has an opposite molecular profile closer to classical papillary thyroid carcinoma than to follicular adenoma/carcinoma (BRAF?>?RAS mutations). Noninvasive encapsulated FVPTC are extremely indolent even if treated with lobectomy without radioactive iodine therapy. Although most EFC are thought to have an excellent outcome, there are cases of EFC that recur and metastasize. EFC with angioinvasion, especially if extensive, have a significant rate of distant recurrence. Encapsulated FVPTC have a molecular profile and a clinical behavior very similar to the follicular adenoma/carcinoma class of tumor. If noninvasive, encapsulated FVPTC should be treated in a very conservative fashion. EFC with angioinvasion, especially if extensive, should not be termed minimally invasive in order to prevent undertreatment of the patient.     

BRAF copy number gains in thyroid tumors detected by fluorescence In Situ hybridization

Point mutation of the BRAF gene is a common genetic event in papillary thyroid carcinomas. More recently, it has been found that BRAF can also participate in chromosomal rearrangement. In this study, we explore yet another possible mechanism of BRAF alteration, which involves copy number gain. Using fluorescence in situ hybridization with BRAF specific and chromosome 7 centromeric probes, we studied 62 follicular thyroid tumors and 32 papillary carcinomas. We found that numerical changes in BRAF copy number were rare in papillary thyroid carcinomas, while they occurred in 16–45% of follicular tumors of conventional and oncocytic (Hürthle cell) types. They were due to amplification of the gene or gain of one or more copies of chromosome 7. Tetrasomy for chromosome 7 was overall the most common finding. The changes in BRAF copy number did not overlap with RAS mutations in follicular tumors. In a group of follicular carcinomas, tumors with BRAF copy number gain were significantly more often widely invasive (67%) compared to tumors with no copy number change (18%). By Western blotting, the tumors carrying four copies of the gene revealed higher expression of BRAF protein, suggesting that copy number gain may represent another mechanism of BRAF activation in thyroid tumors.     

Molecular pathology of thyroid tumours of follicular cells: a review of genetic alterations and their clinicopathological relevance

Thyroid cancer is the most common endocrine malignancy. Knowledge of the molecular pathology of thyroid tumours originating from follicular cells has greatly advanced in the past several years. Common molecular alterations, such as BRAF p.V600E, RAS point mutations, and fusion oncogenes (RET–PTC being the prototypical example), have been, respectively, associated with conventional papillary carcinoma, follicular‐patterned tumours (follicular adenoma, follicular carcinoma, and the follicular variant of papillary carcinoma/non‐invasive follicular thyroid neoplasm with papillary‐like nuclear features), and with papillary carcinomas from young patients and arising after exposure to ionising radiation, respectively. The remarkable correlation between genotype and phenotype shows how specific, mutually exclusive molecular changes can promote tumour development and initiate a multistep tumorigenic process that is characterised by aberrant activation of mitogen‐activated protein kinase and phosphoinositide 3‐kinase–PTEN–AKT signalling. Molecular alterations are becoming useful biomarkers for diagnosis and risk stratification, and as potential treatment targets for aggressive forms of thyroid carcinoma. What follows is a review of the principal genetic alterations of thyroid tumours originating from follicular cells and of their clinicopathological relevance.     

Intraluminal crystalloids in struma ovarii. Immunohistochemical, DNA flow cytometric, and ultrastructural study

We recently encountered a unique case of follicular variant of papillary carcinoma arising in struma ovarii that contained numerous intrafollicular crystalloids. There was no evidence of capsular or vascular invasion or metastases, though the DNA content of the papillary carcinoma was aneuploid. In contrast, diploid DNA was manifested in the histologically benign thyroid tissue. The nature of the crystalloids and the significance of aneuploid DNA content are discussed.     

Case report: Malignant struma ovarii

Struma ovarii are specialized teratomas consisting of thyroid tissue with various microscopic features, ranging from benign to malignant. We report a rare form of malignant struma ovarii, composed exclusively of a follicular variant of papillary thyroid carcinoma with capsular invasion, which occurred in a 65-yr-old woman.     

Predominant Brenner Tumor Combined with Struma Ovarii Containing a Papillary Microcarcinoma Associated with Benign Peritoneal Strumosis: Report of a Case and Histologic Features

Brenner tumor and struma ovarii, two uncommon ovarian tumors arising alone or together with dermoid cysts or adenomas, are both rare entities. Both tumors rarely become malignant and rarely metastasize. Few published reports describe coexisting Brenner tumor and malignant struma ovarii. Patients in whom these malignancies coexist only occasionally have peritoneal spreading, strumosis, or a history of thyrotoxicosis. The patient we describe, a 74-year-old woman, presented with a 2 months’ history of lower abdominal pain and episodic intestinal subocclusion due to a complex pelvic mass. The mass consisted predominantly of a Brenner tumor associated with struma ovarii containing a single small island of thyroid tissue that had undergone malignant transformation into a well-differentiated papillary carcinoma and also normal thyroid tissue that had spread to the peritoneum. The patient underwent radical surgical treatment and after 7 years follow-up is disease free.     

Understanding the genotype of follicular thyroid tumors

Tumors of the thyroid with a follicular growth pattern are controversial and can be diagnostically challenging for the pathologist. This group of tumors includes both follicular-derived lesions (adenomas and carcinomas) and papillary carcinoma (follicular variant of papillary carcinoma). H&E morphology has classically been the gold standard for diagnosis. In the past several decades, however, several important molecular markers have been identified that may be unique to different types of thyroid carcinomas. These include the translocations RET/PTC and PAX8-PPARγ and point mutations in the BRAF and RAS genes. Other molecular events in tumor suppressor genes may be useful for diagnosis of these tumors as well. None of the mutational markers are very sensitive, and there is some question regarding specificity for malignancy, because mutations have also been described in histologically benign tumors. However, with increasing availability of molecular testing for the general pathologist, a molecular testing panel used in conjunction with the H&E morphology and immunohistochemical stains may become useful in the clinical setting for the diagnosis of thyroid tumors.     

<Emphasis Type="Italic">BRAF</Emphasis> mutations typical of papillary thyroid carcinoma are more frequently detected in undifferentiated than in insular and insular-like poorly differentiated carcinomas

Somatic mutations of the BRAF gene (BRAF^V599E and BRAF^K600E) were found to be closely associated with different histotypes of papillary thyroid carcinoma (PTC). The V599E mutation is highly prevalent in PTC with a papillary or mixed papillary follicular growth pattern, and the K600E mutation is apparently restricted to the follicular variant of PTC. It is usually accepted that thyroid malignancies may follow a progression path from well-differentiated to poorly differentiated (PDC) and undifferentiated (UC) carcinomas. One would expect that at least some of the less differentiated carcinomas would harbour the genetic alterations of pre-existing well-differentiated tumours. In order to find the prevalence of BRAF mutations in PDC and UC, we screened a series of 19 PDCs and 17 UCs, as well as 3 UC-derived cell lines, for both mutation types. The group of PDCs was restricted to the so-called insular and insular-like PDCs, thus excluding PTCs with solid, insular or trabecular foci of growth and PDCs displaying typical PTC nuclei. No BRAF mutations were detected in any of the 19 cases of PDC, whereas 6 of the UCs (35%) and one UC-derived cell line presented the BRAF^V599E mutation. The BRAF^K600E mutation was not detected in any case. We conclude that UC may progress from BRAF^V599E-mutated PTC. The absence of BRAF mutations in our series of PDC supports the assumption that pure insular and insular-like PDCs are more closely related to follicular carcinoma than to PTC.Paula Soares and Vítor Trovisco contributed equally to this work.     

<Emphasis Type="Italic">BRAF</Emphasis><Superscript>V600E</Superscript> Mutation in Papillary Thyroid Carcinoma: Significant Association with Node Metastases and Extra Thyroidal Invasion

B-Raf (BRAF) is the strongest activator in the downstream of MAP kinase signaling. The somatic point mutation of BRAF gene (V600E) is the most common and specific event in papillary thyroid carcinoma (PTC). However, its prevalence is variable among different studies and its association with clinico-pathological features is controversial. This study tests the prevalence of BRAF ^V600E mutation in thyroid cancer patients in Indian subcontinental population. We analyzed 140 thyroid tumor specimens for BRAF gene mutation at codon 600 using mutant-allele-specific amplification, single-strand conformation polymorphism, Mutector assay, and DNA sequencing of the PCR-amplified exon 15. BRAF mutation at codon 600 was detected in 46 of 86 PTC patients (53.4%) from Indian subcontinental cohort. Frequency of mutation varied across the subtypes of PTCs. BRAF ^V600E mutation was more common in the conventional PTC (38 out of 62; 61%) than in the follicular variant of PTC (2 out of 17; 11.7%). None of the 8 follicular thyroid adenomas, 14 follicular thyroid carcinomas, 16 medullary thyroid carcinomas, and 16 benign hyperplasia patients showed any exon 15 mutation. We found significant correlation between BRAF mutation status and extra-thyroidal invasion, lymph node metastasis, and tumor stage. However no correlation was observed with gender, age, and tumor size of the patients. Thus our findings suggest that BRAF ^V600E is a prevalent genetic alteration in adult sporadic PTCs in Indian cohort and it may be responsible for the progression of classic variant of PTC to metastatic and poorly differentiated subtype and likely to have significant impact on its diagnostic and prognostic management.     

Malignant struma ovarii: a case report

Malignant struma ovarii is a rare form of the ovarian germ cell tumors. Hence, diagnosis and management of malignant struma ovarii have not been clearly defined. We present the case of a 34-year-old woman with papillary carcinoma arising in struma ovarii. The malignant component of this tumor was detected after laparoscopic removal, and a re-staging operation was performed afterwards. There was no evidence of clinical malignancy or metastases. In this paper, clinical features, treatment guidelines, diagnostic features, and immunohistochemical characteristics of this tumor are reviewed.     

Hyalinizing Trabecular Tumor of the Thyroid: An Update

Hyalinizing trabecular tumor (HTT) is a rare thyroid tumor of follicular cell origin with a trabecular pattern of growth and marked intratrabecular hyalinization. This tumor is known to share morphological and architectural similarities with paraganglioma and medullary thyroid carcinoma, as well as the nuclear features and RET/PTC1 translocations of papillary thyroid carcinoma. These tumors are not associated with RAS or BRAF mutations. Whether the presence of RET alterations in HTT are sufficient molecular proof of its relationship with papillary thyroid carcinoma (PTC) is still to be defined. Of great interest is the characteristic strong peripheral cytoplasmic and membranous staining of the tumor cells with MIB1 immunostain, not seen in any other thyroid neoplasm. Although cases of malignant HTT have been recorded, HTT should be considered a benign neoplasm or, at most, a neoplasm of extremely low malignant potential.     

Absence of BRAF, NRAS, KRAS, HRAS Mutations, and RET/PTC Gene Rearrangements Distinguishes Dominant Nodules in Hashimoto Thyroiditis from Papillary Thyroid Carcinomas

Dominant nodules within Hashimoto thyroiditis (HT) may present with unique morphological features that overlap with but are not diagnostic of papillary thyroid carcinoma (PTC). Activating BRAF point mutations, RAS aberrations, and RET rearrangements are mutually exclusive events in the oncogenesis of papillary thyroid carcinoma, and RET rearrangements have been previously described in dominant nodules of HT. We identified 28 cases of Hashimoto thyroiditis with a dominant nodule, from 345 consecutive HT thyroidectomies. Screening for BRAF, RET, KRAS, NRAS, and HRAS mutations, as well as RET-PTC1 and RET-PTC3 rearrangements, was performed on paraffin-embedded material from 17 of these dominant nodules. Patients ranged in age from 29 to 76 years and were predominantly female, and the nodules ranged from 1.5 to 6.2 cm. No BRAF or RAS mutations or RET-PTC rearrangements were identified in a dominant nodule, including those with atypical, worrisome histopathologic features. Of ten cases with diagnostic concomitant or incidental papillary carcinoma, three had a V600E point mutation in BRAF, and one case had a BRAF exon 15 deletion (600–604E), while the dominant nodules were negative for mutation, supporting the notion that dominant nodules are neither malignant nor precursor lesions, and strict histological, clinical, and molecular criteria must be met for the diagnosis of papillary thyroid carcinoma.