Plasma cell infiltration and treatment effect in breast cancer patients treated with neoadjuvant chemotherapy.

BACKGROUND: Tumour-infiltrating lymphocyte (TIL)-high breast tumours have a high rate of pathological complete response (pCR) with neoadjuvant chemotherapy. In our routine pathological diagnoses of biopsy specimens from pCR cases, we have observed a high infiltration of plasma cells (PCs). A positive correlation of PCs with favourable patient outcome has recently been reported, but little is known about how PCs contribute to local tumour immunity. METHODS: We retrospectively examined biopsy specimens from 146 patients with invasive breast cancer who received neoadjuvant chemotherapy. CD138+ PC infiltration was assessed by immunohistochemistry. Multiplexed fluorescent immunohistochemistry (mfIHC) with T and B cell markers was also conducted to elucidate the profile of immune cells. RESULTS: Greater PC infiltration was observed in the pCR group (p = 0.028) and this trend was confirmed in another patient cohort. With mfIHC, we observed significantly more CD8+, T-bet+CD4+, and CD8+FOXP3+ T cells, total B cells and PCs in pCR cases. Such cases were also characterised by high expression of both PD-1 and PD-L1 on B cells and PCs. In patients with hormone receptor-negative tumours, high PC infiltration was correlated with significantly longer disease-free survival (p = 0.034). CONCLUSIONS: We found that higher PC infiltration in biopsy specimens before neoadjuvant chemotherapy was associated with pCR. With mfIHC, we also revealed that the local cytotoxic immune response was clearly enhanced in pCR cases, as was the infiltration of B cells including PCs. Moreover, higher PC levels were correlated with favourable outcomes in hormone receptor-negative breast cancer patients.

Antitumor effects of novel mAbs against cationic amino acid transporter 1 (CAT1) on human CRC with amplified CAT1 gene.

Copy number alterations detected by comparative genomic hybridization (CGH) can lead to the identification of novel cancer-related genes. We analyzed chromosomal aberrations in a set of 100 human primary colorectal cancers (CRCs) using CGH and found a solute carrier (SLC) 7A1 gene, which encodes cationic amino acid transporter 1 (CAT1) with 14 putative transmembrane domains, in a chromosome region (13q12.3) with a high frequency of gene amplifications. SLC7A1/CAT1 is a transporter responsible for the uptake of cationic amino acids (arginine, lysine, and ornithine) essential for cellular growth. Microarray and PCR analyses have revealed that mRNA transcribed from CAT1 is overexpressed in more than 70% of human CRC samples, and RNA interference-mediated knockdown of CAT1 inhibited the cell growth of CRCs. Rats were immunized with rat hepatoma cells expressing CAT1 tagged with green fluorescent protein (GFP), and rat splenocytes were fused with mouse myeloma cells. Five rat monoclonal antibodies (mAbs) (CA1 ~ CA5) reacting with HEK293 cells expressing CAT1-GFP in a GFP expression-dependent manner were selected from established hybridoma clones. Novel anti-CAT1 mAbs selectively reacted with human CRC tumor tissues compared with adjacent normal tissues according to immuno-histochemical staining and bound strongly to numerous human cancer cell lines by flow cytometry. Anti-CAT1 mAbs exhibited internalization activity, antibody-dependent cellular cytotoxicity, and migration inhibition activity against CRC cell lines. Furthermore, CA2 inhibited the in vivo growth of human HT29 and SW-C4 CRC tumors in nude mice. This study suggested CAT1 to be a promising target for mAb therapy against CRCs.

A collision tumor of solitary fibrous tumor/hemangiopericytoma and meningioma: A case report with literature review.

An intracranial collision tumor is a rare lesion composed of two histologically different neoplasms in the same anatomic location. Even more rare is the collision tumor of a solitary fibrous tumor/hemangiopericytoma (SFT/HPC) and meningioma. The patient was a 46-year-old woman who had a 40 × 35 × 30-mm mass in the vermis of the cerebellum. Histologically, the mass consisted of two different components. One component showed the morphology of meningioma (World Health Organization (WHO) grade I), and the other component exhibited small round cell proliferation with hypercellular density, which was revealed to be SFT/HPC (WHO grade III) based on STAT6 immunohistochemistry. STAT6 showed completely different immunohistochemistry results in these two components (nuclear-negative in meningioma and nuclear-positive in SFT/HPC). Since these two neoplasms are associated with different prognoses, they should be distinguished from each other. When meningioma and an SFT/HPC-like lesion are identified morphologically, it is important to recognize the presence of such a collision tumor composed of meningioma and SFT/HPC, and identify the SFT/HPC component by employing STAT6 immunohistochemistry.

Intravascular ultrasound imaging of isolated and non aorto-ostial coronary Takayasu arteritis: a case report.

BACKGROUND: Isolated coronary Takayasu arteritis is a rare form of ischemic heart disease that typically appears as an aorto-ostial lesion. Although several vascular imaging modalities including ultrasonography, computed tomographic angiography, magnetic resonance angiography or catheter angiography, play crucial roles for diagnosing Takayasu arteritis, the intravascular ultrasound imaging of Takayasu arteritis is not well studied. CASE PRESENTATION: A 55-year-old woman who was diagnosed with heterozygous familial hypercholesterolemia underwent coronary angiography due to effort angina, which showed ostial left anterior descending coronary artery (LAD) stenosis. Although directional coronary atherectomy followed by drug-coated balloon was successfully performed, 6 months later restenosis occurred at the ostial LAD, and the ostial left circumflex coronary artery (LCx) progressed significantly. The intravascular ultrasound imaging in these lesions was noteworthy, in which the media was partly unrecognizable and an echo intensity similar to fibrotic intimal thickening traversed from the intima to the adventitia, thereby causing the whole image of the coronary artery to become unclear. Directional coronary atherectomy followed by drug-coated balloon procedures for both LAD and LCx lesions were performed again. Systemic examination of computed tomographic angiography found no other stenotic lesions except for those in the coronary arteries. Five months later, the LAD and LCx lesions progressed diffusely, therefore the coronary artery bypass graft was done. The histopathological findings of specimens of the coronary artery that were obtained during the bypass graft showed excessive fibrous thickening of the intima and adventitia, with granulomatous inflammation in the media, which led to the diagnosis of isolated coronary Takayasu arteritis. Systemic corticosteroid therapy was then started. CONCLUSIONS: We described an extremely rare case of isolated and non aorto-ostial Takayasu arteritis. The characteristic intravascular ultrasound images of diseased coronary arteries may help in the diagnosis of coronary Takayasu arteritis.

A unique autopsy case of ascending aortic dissection caused by giant cell arteritis without drug therapy.

Giant cell arteritis is a granulomatous inflammation of large and medium-sized arteries, occurring predominantly in older women. In this case, a 76-year-old woman was hospitalized for examination because of a high C-reactive protein (CRP) level, but nothing remarkable was found on thoracicoabdominal computed tomography (CT) or head magnetic resonanse imaging (MRI). On the 46th day from the first visit, she died suddenly due to cardiac tamponade. On pathological autopsy, we found the cause of death to be acute aortic dissection (Stanford type A) due to giant cell arteritis occurred in the ascending aorta. Histologically, granulomatous vasculitis with giant cells was recognized in the ascending aorta, thoracic descending aorta and abdominal aorta and their branches. Interestingly, similar granulomatous vasculitis was also found in the medium and small vessels of other plural organs, including the heart, liver, uterine corpus, and its appendages. To our knowledge, giant cell arteritis with multiple-organ granulomatous changes has not been reported before. We herein reported a unique autopsy case of giant cell arteritis in a patient not treated with medication.

Low-grade intraductal carcinoma of the salivary gland with prominent oncocytic change: a newly described variant.

AIMS: Low-grade intraductal carcinoma (LG-IDC) is a clinically indolent malignant tumour of the salivary glands. Because of its rarity, the histological variants of LG-IDC have not been well characterised. Herein, we describe five LG-IDC cases with prominent oncocytic change in the major salivary glands. METHODS AND RESULTS: We examined five cases, three males and two females (mean age = 63 years), of LG-IDC with oncocytic change. The sites affected by LG-IDC were the parotid and submandibular glands. The lesions were macroscopically unilocular or multilocular cysts with a solid tumour arising from the cyst wall. Smaller tumour cell nests were also observed. As with classic LG-IDC, the cyst wall was surrounded by myoepithelial cells with no invasive component. The tumour cells had abundant oncocytic cytoplasm and proliferated in a low-papillary, tubular or cribriform pattern. Immunohistochemically, the tumour cells were diffusely positive for pan-cytokeratin, S100, mammaglobin and antimitochondria antibody, and were negative for androgen receptor and gross cystic disease fluid protein-15. Unlike classic LG-IDC, some of these cases demonstrated focal invagination of myoepithelial cells in the intraductal tumour. CONCLUSION: Oncocytic LG-IDC should be recognised as a histologically unique variant of LG-IDC. Awareness of this entity is important to avoid erroneous diagnosis and inappropriate treatment for histological mimics.

A Case Report of Superficial Solitary Fibrous Tumor in the Right Parotideomasseteric Region.

Solitary fibrous tumors (SFTs) are rare mesenchymal tumors that occur in various soft tissues and organs throughout the body. Superficial SFTs in the head and neck region are uncommon and reports of such cases are limited. An elderly Japanese woman in her 80s presented to our clinic with a smooth mass in the right parotideomasseteric region. Ultrasonography and magnetic resonance imaging revealed a well-defined subcutaneous mass measuring 20 mm. For a definitive diagnosis and treatment, surgical resection was performed under local anesthesia. Intraoperatively, a brown-colored tumor was identified beneath the skin, without surrounding tissue adhesion, and was completely excised. Immunohistochemistry, revealing the expression of STAT6, confirmed the diagnosis of SFT. Based on the SFT risk classification, this case was classified into the low-risk group, and no recurrence occurred during the 4 year postoperative period. According to the 2020 World Health Organization Classification of Soft Tissue Tumors, SFTs belong to the intermediate category with recurrence potential. In previous studies, cases of positive margins and recurrence have been reported in superficial SFTs, and SFTs may show benign features on clinical presentation but require precise surgical manipulation. Therefore, it is crucial for otolaryngologists to gain a comprehensive understanding of this tumor for appropriate treatment.

Ruptured Saccular Aneurysm Caused by Necrotizing Arteritis of the Polyarteritis Nodosa Type in Primary Angiitis of Central Nervous System.

Primary angiitis of central nervous system (PACNS) is a rare idiopathic vasculitis that typically involves small arteries. An 18-year-old woman was operated on for resection of a ruptured aneurysm in a cerebral artery. Multiple aneurysms of cerebral arteries had been detected by neuroimaging examinations since the age of 12, and she had been administered drugs following a diagnosis of PACNS since the age of 15. The resected aneurysm was a ruptured saccular aneurysm occurring in a medium-sized artery. Histologically, necrotizing arteritis of the polyarteritis nodosa (PAN) type was noted in the aneurysmal wall. It consisted of an admixture of acute and healing stages. In the acute stage, fibrinoid necrosis in the intima and media and intense inflammatory cell infiltrate in the entire wall were present. The inflammatory cells mainly consisted of lymphocytes, including plasma cells, neutrophils, and macrophages. In the healing stage, disappearance of fibrinoid necrosis, fibrosis in the intima and media, and scarce inflammatory cells were noted. The acute stage was mainly present near the ruptured site. From these findings, the aneurysm was considered to have been caused by necrotizing arteritis of the PAN type. Although saccular aneurysmal formation in a medium-sized artery is rare in PACNS, an understanding of aneurysms produced by necrotizing arteritis of the PAN type offers useful information for the diagnosis and treatment of PACNS.

Mixed Mesonephric-like Adenocarcinoma, Clear Cell Carcinoma, and Endometrioid Carcinoma Arising from an Endometriotic Cyst.

Mesonephric-like adenocarcinoma is a rare neoplasm of the uterine corpus and ovary. Unlike prototypical mesonephric adenocarcinoma of the uterine cervix, which is considered of Wolffian origin, recent evidence suggests that mesonephric-like adenocarcinoma is a Mullerian tumor associated with endometriosis. We report here on a 48-year-old woman with a mixed carcinoma of the ovary that consisted of mesonephric-like adenocarcinoma, clear cell carcinoma, and endometrioid carcinoma, arising from an endometriotic cyst. The mesonephric-like adenocarcinoma consisted of cuboidal cells with vesicular nuclei presenting with a tubular, ductal, papillary, and solid architecture forming nodules. Each component showed distinct immunophenotypes that were consistent with their morphology. The mesonephric-like adenocarcinoma showed diffuse positive staining for paired box 8 and GATA binding protein 3, and negative staining for estrogen and progesterone receptors. A p53 stain exhibited wild-type immunoreactivity. A complete loss of AT-rich interactive domain-containing protein 1A (ARID1A) expression was suggestive of an ARID1A mutation. Manual macrodissection and Sanger sequencing revealed identical KRAS and PIK3CA mutations in all three components. To the best of our knowledge, this is the first report of mesonephric-like adenocarcinoma combined with a clear cell carcinoma and endometrioid carcinoma, which supports the hypothesis that mesonephric-like adenocarcinoma is an endometriosis-associated neoplasm. The report also highlights a potential pitfall in diagnosing mesonephric-like adenocarcinoma combined with clear cell carcinoma.

Intraosseous Lipoma of the Calvaria in the Early Stage Resembling Normal Fatty Marrow.

Intraosseous lipoma (IOL) is a benign bone tumor that usually arises from the lower limb and rarely arises from the skull. Radiological diagnosis of a typical case is not problematic due to its characteristic calcification and marginal sclerosis. Here, we report a case of calvarial IOL in the early stage lacking conventional radiopathological features. The patient is a 7-year-old girl who presented with a slow-growing protuberance on the vertex of the head. Computed tomography displayed a low-density mass without calcification that was continuous with the surrounding diploe. The mass was resected piece by piece for diagnostic and cosmetic reasons. Histologically, the specimen consisted of bony trabeculae and intertrabecular adipose tissue, which resembled normal fatty marrow. However, adipose tissue was considered neoplastic since it lacked hematopoietic elements. The final diagnosis of IOL was made by radiopathological correlation. This case suggests that IOL should be included in the differential diagnosis of diploic expansion, even if calcification is absent. The histology of an early-stage IOL resembles normal fatty marrow, but recognizing the absence of hematopoietic elements aids the diagnosis. Also, our literature review indicates that such cases are likely to be encountered in the calvaria than cranial base.

Lymphangiogenesis is a predictor of nodal metastasis in extramammary Paget's disease.

AIMS: The depth of dermal invasion, lymphatic invasion and tumour formation are thought to be predictors of nodal metastasis in extramammary Paget's disease (EPD). This study investigated the relationship between lymphangiogenesis and nodal metastasis in EPD. METHODS AND RESULTS: Fifty cases (12 females and 38 males) with primary EPD of the external genitalia whounderwent surgical resection were studied. In 23 cases, inguinal lymph node dissection was performed, and nodal metastasis was found in eight cases. Lymphatic invasion and lymphangiogenesis were evaluated by D2-40 immunostain. Lymphangiogenesis was observed in 25 cases (50%). There were significant differences in the presence or absence of dermal invasion, depth of invasion, lymphatic invasion and nodal metastasis between the lymphangiogenesis group and non-lymphangiogenesis group. CONCLUSION: Dermal invasion and depth of dermal invasion are predictors for nodal metastasis in EPD. However, in the current study, we demonstrate that lymphangiogenesis is also a predictor of nodal metastasis in EPD.

Histopathologic analysis of intestinal endometriosis after laparoscopic low anterior resection.

STUDY OBJECTIVE: To determine how intestinal endometriosis spreads, and, thus, to improve outcomes of curative surgery. DESIGN: Descriptive study (Canadian Task Force classification II-2). SETTING: University hospital. PATIENTS: Ten patients who underwent laparoscopic low anterior resection of intestinal endometriosis at our hospital between January 1999 and August 2007. INTERVENTION: Laparoscopic low anterior resection of intestinal endometriosis. MEASUREMENTS AND MAIN RESULTS: Mapping of endometriotic foci, degree of vertical infiltration to the intestinal layers, and longitudinal spread of endometriotic foci to the intestinal plane were defined using hematoxylin-eosin, estrogen receptor, progesterone receptor, and CD10 staining. RESULTS: Endometriotic foci tended to spread concentrically around a primary lesion that comprised most of a resected specimen. The deepest layer containing endometriotic foci at the primary lesion was the submucosal layer in 7 specimens (70%), and the internal circular muscle layer in 3 (30%). Satellite lesions comprising thickened areas that were independent of the primary lesion were detected in 5 specimens (50%). Multiple endometriotic foci were confirmed in all satellite lesions. CONCLUSIONS: Endometriotic foci might not only infiltrate the primary lesion in intestinal endometriosis but also disseminate to other areas. Thus, the primary lesion of intestinal endometriosis with a large margin must be excised via low anterior resection.

Dysgerminoma with Estrogen-Producing Functioning Stroma Presenting Precocious Puberty.

Dysgerminoma is a malignant ovarian germ cell tumor, and unlike sex-cord stromal tumors, endocrine manifestation is considered rare. Here, we report the first case of dysgerminoma presenting precocious puberty. The patient is a 7-year-old girl who presented with a breast development in Tanner stage 3. Serum estradiol (E2) was markedly elevated while luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were suppressed below the detection limit. Microscopically, the right ovarian mass displayed nests of large polygonal cells and fibrous septa which were focally concentrated by theca-like plump spindle cells. Immunohistochemistry revealed that the spindle cells expressed various steroidogenic enzymes involved in estrogen biosynthesis including P450 aromatase. The tumor was diagnosed with pure dysgerminoma with estrogen-producing functioning stroma. After the operation, serum E2 declined below the detection limit; LH and FSH returned within the normal range. This case demonstrates that even a conventional dysgerminoma can present endocrine manifestation through functioning stroma.

Molecular and clinicopathological features of appendiceal mucinous neoplasms.

Appendiceal mucinous tumors (AMTs) include low-grade mucinous appendiceal neoplasms (LAMNs), high-grade mucinous appendiceal neoplasms (HAMNs), and mucinous adenocarcinomas (MACs). We collected 51 AMT samples (LAMN: 34, HAMN: 8, MAC: 9). Three of the eight HAMN cases contained LAMN components, and four out of nine MAC cases contained LAMN and/or HAMN components within the tumor. A next-generation sequencing (NGS) cancer hotspot panel was used to analyze 11 pure LAMN, 4 HAMN, and 3 MAC cases. The results revealed KRAS and GNAS as the most frequently mutated genes. Sanger sequencing was then performed to detect KRAS, GNAS, and TP53 mutations in the remaining 31 cases and RNF43 mutations in all cases. KRAS/GNAS and TP53 mutations occurred exclusively in pure LAMNs; however, five LAMN cases had mutations in both KRAS and GNAS. RNF43 mutations almost exclusively occurred with KRAS/GNAS mutations in pure LAMNs. In MAC and HAMN, KRAS/GNAS mutation status was nearly preserved between lower-grade areas. Most of the detected RNF43 mutations was missense type. RNF43 mutations were detected in both components of MAC with lower-grade area; however, RNF43 mutations detected in these two lesions were entirely different. RNF43 mutations were detected in only one of the eight HAMN patients, which was the sole case without pseudomyxoma peritonei (PMP). None of the four MAC patients with RNF43 mutation showed PMP. These findings suggest that RNF43 mutations occur at a later stage of MAC development and do not associate with PMP. Furthermore, a gradual transition from LAMN to MAC via HAMN could be considered.

IgG4-related tumour-forming mastitis with histological appearances of granulomatous lobular mastitis: comparison with other types of tumour-forming mastitis.

AIMS: Sometimes, mastitis needs to be differentiated from carcinoma because of its association with induration and with ultrasound findings (such as low-echo lesions) that resemble those in carcinoma. The aim was to define this type of mastitis and to examine 18 cases to clarify its clinicopathological features. METHODS AND RESULTS: All cases were categorized into three types: non-specific mastitis with neutrophilic infiltration (n = 7); non-specific mastitis with lymphoplasmacytic infiltration (n = 9); and granulomatous lobular mastitis (n = 2). The three types of mastitis presented similar ultrasound findings and shared certain histological features including fibrosis and diffuse or lobulocentric inflammation. Granulomatous lobular mastitis showed specific clinicopathological features including lobulocentric inflammation with giant cells, diffuse IgG4+ plasma cells, and also a high level of serum IgG4. CONCLUSIONS: Granulomatous lobular mastitis could be categorized into IgG4-related and non-IgG4-related granulomatous lobular mastitis. IgG4 immunohistochemistry serum IgG4 might be useful for diagnosis of IgG4-related granulomatous lobular mastitis and could help to avoid overtreatment such as wide excision.

Application of a new histological staging and grading system for primary biliary cirrhosis to liver biopsy specimens: Interobserver agreement.

Recently the authors proposed a new staging and grading system for primary biliary cirrhosis (PBC) that takes into account necroinflammatory activity and histological heterogeneity. Herein is proposed a convenient version of this system. Scores for fibrosis, bile duct loss, and chronic cholestasis were combined for staging: stage 1, total score of 0; stage 2, score 1-3; stage 3, score 4-6; and stage 4, score 7-9. Cholangitis activity (CA) and hepatitis activity (HA) were graded as CA0-3, and HA0-3, respectively. Analysis of interobserver agreement was then conducted. Digital images of 62 needle liver biopsy specimens of PBC were recorded as virtual slides on DVDs that were sent to 28 pathologists, including five located overseas. All participants were able to apply this version in all 62 cases. For staging, kappa was 0.385 (fair agreement) and the concordance rate was 63.9%. For necroinflammatory activity, the kappa and concordance rate were 0.110 (slight agreement) and 36.9% for CA, and 0.197 (slight agreement) and 47% for HA, respectively. In conclusion, this new staging and grading system for PBC seems to be more convenient and practical than those used at present, but more instruction and guidance are recommended for the grading of necroinflammatory activity in practice.

Reactive lymphoid hyperplasia of the liver associated with primary biliary cirrhosis.

BACKGROUND: Although reactive lymphoid hyperplasia (RLH) can be found in various organs, including the gastrointestinal tract, orbit, lung, and skin, its occurrence in the liver is rare. CASE REPORT: We report the case of a 47-year-old RLH woman who was identified with RLH of the liver during clinical follow- up of primary biliary cirrhosis. The mass, found incidentally during a medical examination, appeared on ultrasonogram as a hypoechoic mass in the 7th segment of the liver. Further analyses using composed tomography, magnetic resonance imaging, and angiography suggested malignancy, and we performed lateral segmentectomy of the liver. Histologically, the tumor was composed of lymphoid follicles with germinal centers that expressed kappa and lambda light-chain B-cell markers at equal frequency, and no IgH gene rearrangements were detected in Southern blots. Based on these results, we identified the lesion as RLH. CONCLUSIONS: We suggest that this diagnosis be taken into consideration in other cases involving a space-occupying liver mass associated with autoimmune disease.

Investigation of pathological and clinical features of lupus nephritis in 73 autopsied cases with systemic lupus erythematosus.

The aims of this study were to analyze the clinical and pathological features of lupus nephritis (LN) and examine the association between these features and pathological condition, treatment, and prognosis. Of the 177 systemic lupus erythematosus patients who died while receiving inpatient care at Juntendo University Hospital between 1960 and 2001, we investigated the clinical features, treatment, and pathological features of 73 of these who underwent pathological autopsy and had a clear medical history. We divided these cases into two groups, i.e., those up to 1979 (Group A) and those during and after 1980 (Group B) in order to investigate changes in tendencies by age. We also divided the cases into three groups by time interval between diagnosis and death to investigate long-term prognosis. Uremia was the direct cause of death in 38.9% of cases in Group A and only 10.8% of cases in Group B. Pathological features showed a tendency to change to a sclerotic lesion as the duration of the disorder became longer. Uremia attributable to LN was the direct cause of death in relatively fewer cases, although it is still found in the majority of LN cases and remains a problem requiring stringent management. The treatment of sclerotic lesions may be an issue that needs further attention.

Late recurrence of a papillary thyroid carcinoma 37 years after hemithyroidectomy: Solitary, left cervical lymph node metastasis evident on fluorodeoxyglucose positron-emission tomography/computed tomography images revealing nodular uptake.

In patients with well-differentiated papillary thyroid carcinoma (PTC), late recurrence is very rare. It is unusual that 18F-fluorodeoxyglucose positron-emission tomography/computed tomography (PET/CT) shows hypermetabolic lesions in patients with well-differentiated PTC metastases. We demonstrate an exceptional case exhibiting a first relapse 37 years after hemithyroidectomy to treat PTC. Recurrent metastasis of a PTC should be considered as a differential diagnosis even if the elapsed time from the initial treatment is great. A left cervical lymphadenopathy, which exceptionally exhibited a hypermetabolic lesion on PET/CT, should be considered a metastatically well-differentiated PTC.

Hydrocele of the Canal of Nuck with Endometriosis: Right-Side Dominance Confirmed by Literature Review and Statistical Analysis.

Introduction. The canal of Nuck is an embryological remnant of the peritoneal pouch that extends into the labium majus of women. Hydrocele is the most common presentation, but only a small number of cases are reported in association with endometriosis. Case Presentation. The patient is a 45-year-old woman who presented with left inguinal mass with persistent pain. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a 30 mm cystic mass, and a hydrocele of the canal of Nuck (HCN) was suspected. The excised mass was a cyst containing yellow-tan serous fluid, and the cyst wall was lined by mesothelium. The morphology was consistent with conventional HCN. However, since several foci of endometrial-like epithelium and stroma were identified beneath the mesothelium, the mass was diagnosed with HCN with endometriosis (EM-HCN). Discussion. Right-side dominance of EM-HCN is suggested by several authors, but a thorough review has never been performed. For the first time, we reviewed the literature and statistically confirmed that EM-HCNs dominantly occur on the right side compared to those without endometriosis. We consider that this supports the theory that endometriosis derives from retrograde menstruation of endometrial tissue through fallopian tubes. When endometriosis is discovered in HCN, the clinician should be aware of the possibility of pelvic endometriosis.