Struma ovarii with Hashimoto's thyroiditis: case report and review of the literature.

Background: Struma ovarii, a rare ovarian neoplasm originating from germ cells within mature teratomas, typically manifests benign characteristics. However, instances of malignant transformation have been documented. Case description: This report discusses a 25-year-old woman who had surgery in May 2020 to remove teratomas from both ovaries. In 2023, an ultrasound showed a complex mass in her pelvis. Further imaging tests, including CT, MRI, and F-18 FDG PET/CT scans, along with high levels of the CA 125 protein, suggested a mass in her left ovary, initially thought to be ovarian cancer. However, a closer examination after surgery found thyroid tissue and several types of cell growth but no cancer, confirming the diagnosis of struma ovarii. The pathology of hypermetabolic thyroid nodules on F-18 FDG PET/CT confirmed Hashimoto's thyroiditis. Conclusion: This case underscores the importance of considering struma ovarii in the differential diagnosis of ovarian masses, especially in patients with a history of teratomas. It highlights the challenges in distinguishing struma ovarii from ovarian cancer due to similar clinical signs and imaging. Struma ovarii can be associated with Hashimoto's thyroiditis.

Recurrent malignant struma ovarii presenting as peritoneal carcinomatosis in the setting of an intact thyroid: A case report and review of the literature.

Malignant struma ovarii is an exceedingly rare pathology with a paucity of established criteria regarding management and surveillance with recommendations largely based on case reports and retrospective data. Many authors have supported stratification of malignant struma ovarii into low vs high-risk disease with more conservative management reserved for those deemed low-risk. Here we present a unique case of recurrent metastatic malignant struma ovarii after surveillance was undertaken in the setting of initially low-risk disease.

A rare case of retroperitoneal teratoma with evidence of papillary thyroid carcinoma: a case report.

BACKGROUND: Teratomas are germ cell tumors composed of somatic tissues from up to three germ layers. Primary retroperitoneal teratomas usually develop during childhood and are uncommon in adults and in the retroperitoneal space. While there are only a few cases of retroperitoneal thyroid tissue, we report a unique case of a retroperitoneal papillary thyroid carcinoma. CASE PRESENTATION: A 41-year-old woman presented in our institution due to intermitted unspecific abdominal pain. Magnetic resonance imaging detected a multi-cystic solid retroperitoneal mass ventral to the psoas muscle and the left iliac artery. After surgical removal of the retroperitoneal mass, histology sections of the specimen indicated evidence of papillary thyroid carcinoma cells. A staging computed tomography scan of the body showed no further manifestations. To reduce the risk of recurrence, total thyroidectomy was performed followed by radioiodine therapy with lifelong hormone substitution. CONCLUSIONS: Primary retroperitoneal teratoma with evidence of papillary thyroid carcinoma is a rare condition. Preoperative diagnosis is difficult due to its non-specific clinical manifestation and lack of specific radiologic findings. Histopathology analysis is necessary for diagnosis. Although surgery is considered the first line treatment, there is still discussion about the extent of resection and the need for total thyroidectomy with adjuvant radioiodine therapy.

Clinical Manifestations of Malignant Struma Ovarii: A Retrospective Case Series in a Tertiary Hospital in Korea.

BACKGRUOUND: Malignant struma ovarii (MSO) is a very rare disease in which thyroid cancer originates from the ovary. Because it is rare for endocrinologists to encounter patients with MSO, endocrinologists may have a limited understanding of the disease. Therefore, we analyzed and introduced its incidence and clinical course in a tertiary hospital in Korea. METHODS: We retrospectively investigated the clinical data of 170 patients who underwent surgery for struma ovarii at the Department of Obstetrics and Gynecology of Samsung Medical Center from 1994 to May 2023. RESULTS: Among 170 patients with struma ovarii, 15 (8.8%) were diagnosed with MSO. The median age of patients with MSO was 48 years (range, 30 to 74), and the median tumor size was 3.3 cm (range, 0.5 to 11.0). Papillary thyroid carcinoma (46.7%) was the most common subtypes followed by follicular thyroid carcinoma (26.7%). All patients were diagnosed after surgery, with no predictions from preoperative imaging. The surgical extent of gynecological surgery was variable. Four patients (26.7%) underwent thyroidectomy for thyroid cancer, while one underwent total thyroidectomy and radioactive iodine therapy for MSO with peritoneal metastasis. Except for one patient who underwent hemithyroidectomy, thyroid stimulating hormone suppression therapy was performed in four patients. Only 53% of MSO patients were consulted by an endocrinologist. With a median follow-up period of 33 months (range, 4 to 156), 11 patients remained disease-free, one experienced progression with peritoneal seeding, and the remaining one was in treatment. There have been no recurrences or deaths due to MSO. CONCLUSION: An endocrinologist should be involved in establishing a therapeutic plan for MSO, for which the overall prognosis is generally favorable.

Presentation and treatment of two cases of malignant struma ovarii.

BACKGROUND: Malignant Struma Ovarii (MSO) is a rare type of germ cell tumour which is diagnosed postoperatively on surgical pathology specimens by the presence of differentiated thyroid cancer in mature cystic teratomas in the ovaries. Treatment and follow-up procedures are not clearly established due to the paucity of MSO cases. CASE 1: A 44-year-old multiparous female presented with an irregular period. Ultrasound showed a left ovarian lesion mostly a dermoid cyst, however, CT showed a 3.8 × 2.7 × 4 cm complex cystic lesion with thick septation and enhancing soft tissue component. Laparoscopic left salpingo-oophorectomy was performed and histopathology showed a follicular variant of papillary thyroid carcinoma arising in a mature cystic teratoma. Peritoneal cytology was positive for malignancy. A thyroid function test was normal before surgery. Total thyroidectomy was performed followed by radioactive (RAI) iodine therapy. Later, a total laparoscopic hysterectomy and right salpingo-oophorectomy were performed. There is no evidence of recurrent disease during the 26-months follow-up. CASE 2: A 46-year-old single female presented with left lower abdominal pain that had persisted for 2 months. Imaging revealed an 8 × 9 × 9.5 cm left ovarian mass. Laparoscopic left salpingo-oophorectomy was performed and histopathology showed mature cystic teratoma with small papillary thyroid cancer. CT showed no evidence of metastatic disease. Later, the patient had a total thyroidectomy followed by radioactive (RAI) iodine therapy. She was started on thyroxine and later had total abdominal hysterectomy and right salpingo-oophorectomy. CONCLUSION: MSO is a very rare tumour. Preoperative diagnosis is very difficult because of the nonspecific symptoms and the lack of specific features in imaging studies. Also, there is no consensus on the optimal treatment of women with MSO. Our two cases add to the limited number of MSO cases.

Identification of Germline FOXE1 and Somatic MAPK Pathway Gene Alterations in Patients with Malignant Struma Ovarii, Cleft Palate and Thyroid Cancer.

Germline variants in the FOXE1 transcription factor have been associated with thyroid ectopy, cleft palate (CP) and thyroid cancer (TC). Here, we aimed to clarify the role of FOXE1 in Portuguese families (F1 and F2) with members diagnosed with malignant struma ovarii (MSO), an ovarian teratoma with ectopic malignant thyroid tissue, papillary TC (PTC) and CP. Two rare germline heterozygous variants in the FOXE1 promoter were identified: F1) c.-522G>C, in the proband (MSO) and her mother (asymptomatic); F2) c.9C>T, in the proband (PTC), her sister and her mother (CP). Functional studies using rat normal thyroid (PCCL3) and human PTC (TPC-1) cells revealed that c.9C>T decreased FOXE1 promoter transcriptional activity in both cell models, while c.-522G>C led to opposing activities in the two models, when compared to the wild type. Immunohistochemistry and RT-qPCR analyses of patients' thyroid tumours revealed lower FOXE1 expression compared to adjacent normal and hyperplastic thyroid tissues. The patient with MSO also harboured a novel germline AXIN1 variant, presenting a loss of heterozygosity in its benign and malignant teratoma tissues and observable ß-catenin cytoplasmic accumulation. The sequencing of the F1 (MSO) and F2 (PTC) probands' tumours unveiled somatic BRAF and HRAS variants, respectively. Germline FOXE1 and AXIN1 variants might have a role in thyroid ectopy and cleft palate, which, together with MAPK pathway activation, may contribute to tumours' malignant transformation.

Role of gene sequencing in classifying struma ovarii: BRAF p.G469A mutation and TERT promoter alterations favour malignant struma ovarii.

AIMS: Struma ovarii (SO) are rare, accounting for 0.3-1% of ovarian tumours, and include benign and malignant lesions. In most cases, histology is not predictive of clinical outcome and prognosis. The prognosis of histologically malignant thyroid-type carcinomas can indeed be excellent, while SO, composed of normal thyroid tissue, can recur and are designated highly differentiated follicular carcinoma of the ovary. Clearer diagnostic criteria are therefore required. METHODS AND RESULTS: We retrospectively studied 31 SO using DNA and RNA sequencing with pan-cancer gene panels, including eight biologically malignant SO (BMSO) defined based on ovarian serosal or extra-ovarian dissemination at presentation or during follow-up, 10 stage IA histologically malignant SO (HMSO) with thyroid-type carcinoma morphology and 13 biologically and histologically benign SO (BSO), with none of the above-mentioned characteristics. Molecular alterations were observed in 87.5% of BMSO, 70% of HMSO and 7.7% of BSO (P < 0.001). All patients with a peritoneal dissemination at presentation or during follow-up had at least one gene alteration. BRAF mutations (44.5%) were only observed in malignant forms (HMSO and BMSO) and TERT promoter alterations (25%) only in cases of BMSO. The BRAF p.G469A mutation, which is extremely rare in thyroid carcinomas, was the molecular alteration most frequently associated with malignant SO (28.5%). CONCLUSION: Our results highlight the clinical utility of molecular sequencing in SO, based on this limited number of cases. However, as malignant SO evolve slowly, more extensive molecular studies in SO with more than 10 years' follow-up are required to draw any conclusions on the prognostic value of the associated gene alterations.

Thyroid Carcinoma Arising From Struma Ovarii at Adolescence: A Challenging Case With Favorable Outcome.

Malignant struma ovarii (MSO) is a rare and aggressive ovarian tumor that mostly affects adults but can occur in adolescents. Prompt recognition, accurate diagnosis, and multidisciplinary management are essential for favorable outcomes. Herein, we report the youngest case of an 11-year-old girl with a large MSO. First, conventional imaging revealed a large left ovarian mass, leading to a left oophorectomy. Subsequently, histopathological examination confirmed papillary thyroid carcinoma within MSO. Thyroid and fertility-preserving surgery were chosen after multidisciplinary consultation. Despite challenges, the patient had a positive outcome with no recurrence after 36 months. Therefore, the adoption of less invasive surgical approaches and vigilant follow-up can achieve remission, but more research is needed to further enhance our understanding of the disease's risk stratification and optimal treatment strategies.

An Extremely Rare Case of Poorly Differentiated Thyroid Carcinoma Arising in Malignant Struma Ovarii and Concurrent Papillary Thyroid Carcinoma: A Case Study.

Ovarian tumors can be classified by their origin - epithelial tumors, germ cell tumors, and stromal tumors. Malignant struma ovarii (MSO) are 0.01% of all ovarian tumors. In order to be classified as a struma ovarii, more than 50% of the teratoma consists of thyroid tissue. The thyroid tissue in the struma ovarii exhibits the same histological and physiological properties as that of the cervical thyroid tissue. Poorly differentiated thyroid carcinoma (PDTC) is an extremely rare occurrence when arising from an MSO. Including this case report, there are only 10 reports of PDTC in the setting of MSO. Of these cases, this patient is the only one who presented with concurrent primary thyroid carcinoma (PTC). This case study examines how invaluable intra-professional collaboration is for appropriate diagnosis, along with attention to detail of identifying markers in pathology sections and use of the appropriate immunohistochemical analysis.

Incidence, clinical characteristics, and survival outcomes of ovarian strumal diseases: a retrospective cohort study.

BACKGROUND: Struma ovarii (SO) is a rare tumor and may transform into ovarian strumal carcinoid (OSC) and/or malignant struma ovarii (MSO), but the incidence, clinical characteristics, and survival outcomes have not been well defined. METHODS: We conducted a retrospective study of patients with ovarian strumal diseases treated in the our hospital between 1980 and 2022. Subgroup analyses of SO, OSC, and MSO were subsequently performed. RESULTS: A total of 275 cases (2.14%) were identified in a cohort of 12,864 patients with ovarian teratomas, where SO, OSC, and MSO accounted for 83.3%, 12.0%, and 4.7% of cases, respectively. There were no significant differences in age, tumor sizes, elevated tumor markers, and ascites among the three subgroups. At initial treatment, all patients with SO or OSC had FIGO stage I disease except one SO patient presenting metastatic disease, ten patients had MSO confined to the ovary, whereas other three patients had metastatic diseases. Two patients with SO respectively relapsed at peritoneum and anterior mesorectum, while none of the OSC patients presented tumor recurrence or death despite different surgical procedures employed. The 5-year recurrence-free survival rate was 88.9%, and only one death occurred at 9.5 years after diagnosis in patients with MSO. Radioiodine therapy showed satisfactory therapeutic efficacy, but these patients showed poor responses to the chemotherapy. CONCLUSION: 2.14% of ovarian teratoma could be classified as SO, of which 12.0% and 4.7% of SO may transform into OSC and MSO, repsectively. The survival outcomes were excellent even after SO transformed into OSC or MSO. SYNOPSIS: SO occupied 2.14% of ovarian teratoma, where 12.0% and 4.7% of SO may transform into OSC and MSO, respectively, and had excellent survival outcomes.

Concurrent Intrathyroidal Follicular Variant of Papillary Thyroid Carcinoma with Malignant Struma Ovarii Presenting 12 Years After Initial Diagnosis.

Malignancy in struma ovarii is rare and observed in only 5%-10% of patients. Here, we present a patient with malignant struma ovarii and coexisting intrathyroidal papillary thyroid carcinoma, with recurrence (large pouch-of-Douglas mass) and metastases (bilateral pulmonary and iliac nodal metastases) presenting 12 y after surgery. The notable features in this case were a concurrent intrathyroidal follicular variant of papillary carcinoma; the highly functioning nature of the malignant lesions, characterized by a low level of thyroid-stimulating hormone even without thyroxine suppression; and the low-grade 18F-FDG avidity of these lesions, consistent with their well-differentiated nature. With the adoption of a multimodality approach (surgery, radioiodine scintigraphic evaluation, and multiple radioiodine therapies), the patient showed a progressive decrease in the functionality of the disease, prolonged progression-free survival, and a good quality of life with symptom-free status at 5 y.

Synchronous thyroid cancer and malignant struma ovarii: concordant mutations and microRNA profile, discordant loss of heterozygosity loci.

BACKGROUND: Struma ovarii is an unusual ovarian teratoma containing predominantly thyroid tissue. Less than 10% of cases undergo malignant transformation in the thyroid tissue and are considered malignant struma ovarii (MSO). MSO have been reported with concurrent thyroid lesions, but molecular data is lacking. CASE PRESENTATION: A 42-year-old female developed MSO and synchronous multifocal subcentimeter papillary thyroid carcinoma (PTC). The patient underwent a salpingo-oophrectomy, thyroidectomy, and low-dose radioactive iodine ablation. Both the thyroid subcentimeter PTC and MSO were positive for BRAF V600E mutation, and microRNA expression profiles were similar across all tumor deposits. However, only the malignant component demonstrated extensive loss of heterozygosity (LOH) involving multiple tumor suppressor gene (TSG) chromosomal loci. CONCLUSIONS: We present the first reported case of MSO with synchronous multifocal subcentimeter PTC in the thyroid containing concordant BRAF V600E mutations and resulting with discordant LOH findings. This data suggests that loss of expression in tumor suppressor gene(s) may be an important contributor to phenotypic expression of malignancy.

Computed tomography, magnetic resonance imaging, and positron emission tomography/computed tomography findings for the diagnosis of malignant struma ovarii: A case report.

Malignant struma ovarii (MSO) is an extremely rare disease arising from struma ovarii. Preoperative diagnosis is still challenging due to the lack of criteria for imaging findings. Herein, we report a case of MSO with suggestive imaging findings for a 50-year-old woman who presented with a pelvic tumor. The tumor did not typically show characteristic imaging findings of struma ovarii; however, the findings implied colloids of thyroid tissue within solid components on the magnetic resonance imaging (MRI) and computed tomography. Additionally, the solid components showed hyperintensity on diffusion-weighted image and hypointensity on apparent diffusion coefficient maps. Total abdominal hysterectomy, bilateral salpingo-oophorectomy, and omentectomy were performed. Histopathological examination revealed MSO of the right ovary, pT1aNXM0. The distribution of papillary thyroid carcinoma tissue corresponded to restricted diffusion area on MRI. In conclusion, the coexistence of imaging findings suggesting thyroid tissue and restricted diffusion in the solid component on MRI could indicate MSO.

Malignant struma ovarii with thyroid-type papillary and poorly differentiated carcinoma: a case report.

BACKGROUND: Malignant struma ovarii is a very rare type of gynecologic cancer. Although its most common histological subtype is a pure type of papillary thyroid carcinoma containing two components, papillary carcinoma and poorly differentiated carcinoma, malignant struma ovarii is still extremely rare. As a result, the optimal treatment for this type of tumor remains uncertain due to its rarity. CASE PRESENTATION: A 62-year-old Japanese female presented with a pelvic tumor and clinical diagnosis of malignant tumor of the ovary. She underwent complete debulking surgery, total abdominal hysterectomy, bilateral salpingo-oophorectomy, and omentectomy. The histology of the ovarian tumor revealed malignant struma ovarii with thyroid-type papillary projections and poorly differentiated carcinoma. Because of the complete resection and the absence of distant metastasis, the patient did not receive any adjuvant therapy. At 24 months after surgery, she was free of disease. CONCLUSION: This is a rare case report of malignant struma ovarii, without recurrence, in which the component was papillary thyroid carcinoma mixed with poorly differentiated carcinoma. Foregoing adjuvant therapy might be one option for malignant struma ovarii in cases with complete resection and no distant metastasis. In addition, we should consider that long-term follow-up is needed for malignant struma ovarii.

High dose Radioiodine Therapy Preceded by Fertility Preservation Surgery in Metastatic Malignant Struma Ovarii: A Tale of Endurance and Prudent Management.

Struma ovarii is a type of mature ovarian teratoma which accounts for roughly 0.5%-1% (1) of all ovarian tumours and approximately 3% of all ovarian teratomas (2). To be classified as struma ovarii, more than 50% of the tumour must be comprised of thyroid tissue (3). Malignant struma ovarii being rare, no proper guidelines exists regarding its surgical approach or postoperative management. Metastatic malignant struma ovarii, in addition to radical surgery for ovarian mass will require total thyroidectomy to facilitate high dose radioiodine therapy. Here we present the case of a newly married, nulliparous, young lady in her third decade who was diagnosed with malignant struma ovarii with metastatic deposits in fallopian tube and extensive deposits in mesentery and peritoneum., She underwent cryopreservation of embryos followed by bilateral salphingo-oopherectomy + omentectomy + stripping of peritoneum over bladder, abdominal side walls, pelvic peritoneum + appendectomy with preservation of uterus. Total thyroidectomy was done simultaneously. Subsequently she underwent high dose radioiodine therapy. Complete ablation of the residual metastatic deposits were achieved by one sitting of therapy.

Management of malignant struma ovarii: is aggressive therapy justified? Case report and literature review.

BACKGROUND: Struma ovarii (SO) is a rare ovarian teratoma containing predominantly thyroid tissue. In rare situations SO may develop malignancy. Most cases of malignant struma ovarii (MSO) are diagnosed after surgical removal, based on histopathological examination. There are still controversies regarding the extent of surgery and postoperative management in MSO, due to its unpredictable behavior, possible risk of metastasis and relatively high rate of recurrence. CASE PRESENTATION: We present the case of a patient diagnosed with a right ovarian cyst discovered incidentally during routine ultrasound examination. Its rapid growth and pelvic MRI raised the suspicion of a neoplastic process. She underwent total hysterectomy and bilateral adnexectomy. The anatomopathological diagnosis was MSO with follicular variant of papillary thyroid carcinoma. Prophylactic total thyroidectomy was performed, followed by radioactive iodine ablation (RAI), and suppressive therapy with levothyroxine. At 1 year follow-up, the patient was disease free. CONCLUSIONS: Even if latest literature reports consider that completion of local surgery with total thyroidectomy and RAI might be too aggressive in cases of MSO without extraovarian extension, in our case it was decided to follow the protocol for primary thyroid carcinoma, in order to reduce the recurrence risk.

Proposed Risk Stratification and Patterns of Radioactive Iodine Therapy in Malignant Struma Ovarii.

Introduction: Malignant struma ovarii (MSO) is a rare thyroid cancer arising within an ovarian teratoma. While surgical excision of the primary tumor is widely accepted as standard of care, recommendations for adjuvant treatment of MSO-whether or not to administer radioactive iodine (RAI)-are based largely on case reports and remain debated. In this study, we aimed to propose a risk stratification and analyze RAI utilization patterns in MSO cases. Methods: The National Cancer Database (NCDB) was queried for patients with MSO between 2004 and 2016. Demographic, oncological, and clinicopathologic data were compared between groups using Fisher's exact test. Kaplan-Meier curves were used to estimate overall survival (OS), and variables associated with OS were assessed via univariate Cox regression. We adapted the 2015 American Thyroid Association risk guidelines for MSO patients. We stratified patients into low-, intermediate-, and high-risk groups using metastasis, extraovarian extension, lymphovascular invasion, lymph node status, surgical margins, tumor size, and grade. Risk stratification, demographic, oncological, and clinicopathologic data were compared between the groups receiving and not receiving RAI therapy. We then queried the Surveillance, Epidemiology, and End Results (SEER) 18 registry for patients with MSO between 2000 and 2018 to confirm our risk stratification analysis. Results: In the NCDB analysis, a total of 158 patients were identified, and 19 received RAI. RAI therapy was associated with distant metastasis (p = 0.005) and lymph node status (p = 0.012). Twenty-one NCDB patients were stratified as high risk, and 30% of high-risk patients received RAI. High-risk stratification was associated with decreased OS via univariate Cox regression (hazard ratio = 4.0 [95% confidence interval 1.11-14.26], p = 0.034). In our subsequent analysis using the SEER registry, there were 95 MSO patients, and 18 received RAI. Again, the majority of high-risk patients did not receive RAI, with only 41% of high-risk patients receiving RAI. Conclusions: MSO is a rare malignancy with apparently variable and inconsistent patterns of postoperative RAI administration. The risk stratification described here provides a framework to identify patients potentially at risk for mortality, and utilization of RAI in this group should be studied further.

A rare case of highly differentiated follicular carcinoma in ovary with FGFR4 Gly388Arg polymorphism: a case report and literature review.

BACKGROUND: Highly differentiated follicular carcinoma (HDFCO) is a rare form of struma-derived thyroid-type carcinoma in ovary, defined as ovarian struma spreading beyond ovary but consisting of benign thyroid tissues. No more than 30 cases of HDFCO have been reported since it was first recognized in 2008. The clinicopathologic and molecular features of HDFCO remain unclear up till now. CASE PRESENTATION: A 38-year-old, para 1 gravida 5 woman has a long history of recurrent right ovarian cysts. Histological evaluation showed the tumor progressed from ovarian mature cystic teratoma (OMCT) to highly differentiated follicular carcinoma (HDFCO) during three relapses. Whole-exome sequencing revealed the germline FGFR4 Gly388Arg polymorphism. Repeated operations were performed to remove lesions for the first two relapses. On the third recurrence, the patient received radical surgery with subsequent thyroidectomy and radioactive iodine ablation. No evidence of disease was observed by February 2022 (8 months). CONCLUSIONS: The germline FGFR4 Gly388Arg polymorphism may accelerate the malignant transformation of HDFCO, probably by working as a second hit in the developing spectrum.

Malignant struma ovarii with papillary carcinoma combined with retroperitoneal lymph node metastasis: A case report.

BACKGROUND: Struma ovarii is a rare specific ovarian tumor. It is a highly differentiated monodermal teratoma with a malignant transformation rate as low as 5%. Thus, malignant transformation and metastasis are extremely rare. The clinical manifestations of this disease are not typical and are easily misdiagnosed. CASE SUMMARY: A 55-year-old female patient had a history of pain in the right hepatic region for approximately 1 year. Computed tomography and magnetic resonance imaging showed a solid cystic mass in the right adnexal region and a solid mass in the right retroperitoneum. The patient underwent surgical resection, and the combined morphological and immunohistochemical results led to the final diagnosis of right struma ovarii with papillary carcinoma and right retroperitoneal lymph node metastasis. CONCLUSION: Malignant struma ovarii with distant metastasis is extremely rare, and the clinical manifestations of this disease are nonspecific. Accurate preoperative diagnoses are difficult to obtain, and pathological examination is the gold standard for diagnosing this disease.