Renal medullary carcinoma is a rare, high-grade carcinoma arising in the renal medulla, which is usually associated with sickle cell trait, and there are very few documented cases in the Japanese population. We report a case of renal medullary carcinoma, immunohistochemically defined as SMARCB1 deficient, in a 67-year-old Japanese woman without a history of sickle cell trait. Somatic mutation of SMARCB1 and an EML4::ALK fusion gene were identified by comprehensive genomic profiling. Computed tomography revealed metastatic lesions in the retrocaval lymph nodes, liver, and bronchus. Six cycles of the dose-dense methotrexate, vinblastine, adriamycin, and cisplatin-combined chemotherapy were completed after an ultrasound-guided percutaneous biopsy of the renal tumor. After chemotherapy, the size of the original tumor in the right kidney had decreased in size, as well as the other metastatic lesions.

The study investigated the expression of GATA3, a transcription factor involved in immune regulation, in tubo-ovarian carcinomas and its association with clinicopathological factors and prognosis. Immunohistochemical analysis was performed on 91 tubo-ovarian carcinoma samples to determine the presence of GATA3-positive inflammatory cells in the tumor microenvironment. A threshold of 10% or higher was considered a positive expression. The results showed that 46.7% of tubo-ovarian carcinomas exhibited positive expression of GATA3 in inflammatory cells. There was no significant difference in GATA3 expression between patients who received pre-surgical chemotherapy and those who underwent primary surgery. However, high-grade serous carcinomas had a significantly higher proportion of GATA3-positive inflammatory cells compared to other subtypes. Advanced-stage tumors (stage III) had a higher percentage of GATA3-positive inflammatory cells compared to stage II and I tumors. Patients with positive GATA3 expression had a significantly lower disease-free survival rate. However, there was no significant association between GATA3 expression and chemotherapy response score. These findings suggest that increased expression of GATA3 in mononuclear inflammatory cells is associated with higher grade, advanced stage, and increased risk of recurrence in tubo-ovarian carcinoma. This implies that heightened GATA3 expression negatively impacts anti-tumor immunity, tumor growth progression, and invasiveness in tubo-ovarian carcinomas.

Primary mediastinal apocrine adenocarcinoma is extremely rare, with only one case reported to date. Here, we report a surgical case of primary mediastinal apocrine adenocarcinoma. An anterior mediastinal cystic tumor with calcification was identified on chest computed tomography scan in a 51-year-old female patient undergoing maintenance hemodialysis. The tumor was 19 mm in size, did not invade the adjacent organs or show distant metastases, and was surgically removed. Microscopic examination revealed that the tumor cells exhibited cribriform or solid proliferation patterns with thick fibrous capsules. The tumor cells had an abundant eosinophilic cytoplasm, and decapitation secretion was noted. Immunohistochemistry revealed positivity for GCDFP-15 and androgen receptors, with Ki-67 positivity at 10%. The cyst wall exhibited extensive fibrosis and keratinized material, with bone and bronchial glands identified at the cyst periphery; the tumor cells were contiguous with those structures. The patient was diagnosed with apocrine adenocarcinoma arising from a mature cystic teratoma. The patient has maintained a recurrence-free status without adjuvant therapy for 6 years after surgery. This case presents a small primary mediastinal apocrine adenocarcinoma that achieved remarkable long-term survival.

Most elements of filamentous fungi seen in human tissue by pathologists are hyphae, and encountering other elements may interfere with diagnosis. Sporangia and chlamydospores are such elements that have been described in only a few case reports. We present an autopsy case with the extremely rare coexistence of Mucorales sporangia and chlamydospores in the lung. These fungal elements must be recognized and identified accurately because they can easily be mistaken for other fungi, microorganisms, or degenerated tissue structures.

Glioneuronal and neuronal tumors (GNTs) are slow-growing, lower-grade neuroepithelial tumors characterized by mature neuronal differentiation and, less consistently, glial differentiation. Their identification has traditionally relied on histological proof of neuronal differentiation, reflecting the well-differentiated nature of GNTs. However, after discovering genetic alterations in GNTs, particularly those in the MAP-kinase pathway, it became evident that histological diagnoses do not always correlate with genetic alterations and vice versa. Therefore, molecular-based classification is now warranted since several inhibitors targeting the MAP-kinase pathway are available. The World Health Organization classification published in 2021 applied DNA methylation profiling to segregate low-grade neuroepithelial tumors. As GNTs are essentially indolent, radical resection and unnecessary chemoradiotherapy may be more harmful than beneficial for patients. Preserving tumor tissue for potential future treatments is more important for patients with GNTs.

We report a case of adult T-cell leukemia/lymphoma (ATLL) with angioimmunoblastic T-cell lymphoma (AITL/nTFHL-AI)-like feature. An 88-year-old Japanese woman with seropositive for the Human T-lymphotropic virus type 1 (HTLV-1) was incidentally diagnosed with generalized lymphadenopathy. Biopsy of the cervical lymph node demonstrated the proliferation of small- or medium-sized and large atypical lymphocytes associated with eosinophils, high endothelial venules, and clear cells. Immunohistochemical analysis revealed atypical lymphocytes were CD3- and CD4-positive. Atypical T cells bore the T-follicular helper phenotype (PD1, ICOS, and BCL6) and were positive for CD25 and chemokine receptor 4. Epstein-Barr virus encoded RNA-positive cells were scattered in the background via in situ hybridization. The histological findings were similar to those of AITL/nTFHL-AI; however, the immunohistochemical results did not exclude the possibility of ATLL. Southern blot analysis detected integration of HTLV-1 proviral DNA. The RHOA Gly 17 Val (G17V) mutation was detected by the peptide nucleic acid-locked nucleic acid clamp method. Finally, the patient was diagnosed with ATLL with AITL-like feature and exhibited a similar morphology, immunophenotype, and mutational signature to AITL/nTFHL-AI. ATLL mimics other types of T-cell lymphomas. Thus, in HTLV-1 endemic areas, routine screening for HTLV-1 serology is necessary to avoid misdiagnosis of other lymphoid malignancies.

This study aimed to validate the DFS (direct fast scarlet) staining in the diagnosis of EC (eosinophilic colitis). The study included 50 patients with EC and 60 with control colons. Among the 60 control samples, 39 and 21 were collected from the ascending and descending colons, respectively. We compared the median number of eosinophils and frequency of eosinophil degranulation by HE (hematoxylin and eosin) and DFS staining between the EC and control groups. In the right hemi-colon, eosinophil count by HE was useful in distinguishing between EC and control (41.5 vs. 26.0 cells/HPF, p < 0.001), but the ideal cutoff value is 27.5 cells/HPF (high-power field). However, this method is not useful in the left hemi-colon (12.5 vs. 13.0 cells/HPF, p = 0.990). The presence of degranulation by DFS allows us to distinguish between the groups even in the left hemi-colon (58% vs. 5%, p < 0.001). DFS staining also enabled a more accurate determination of degranulation than HE. According to the current standard to diagnose EC (count by HE staining ≥20 cells/HPF), mucosal sampling from left hemi-colon is problematic since the number of eosinophils could not be increased even in EC. Determination of degranulated eosinophils by DFS may potentiate the diagnostic performance even in such conditions.

Diagnosing the cause of death can be challenging, particularly for patients with no prior history of visits to the treating hospital. We encountered a case involving a 76-year-old male who was discovered in a state of cardiopulmonary arrest at his home and subsequently declared deceased in our hospital due to severe pneumonia. He had exhibited symptoms of fever over 37°C and severe coughing for several days. Despite consulting a primary care physician one day prior, his symptoms worsened. Autopsy findings revealed an increase in lung weight and diffuse changes in parenchyma. Histological analysis showed numerous inflammatory cells and exudate within the alveoli. Gram and Periodic acid-Schiff staining were negative, but slight staining was observed in the cytoplasm of macrophages by Warthin-starry and Gimenez stains. Tests using a pan bacterial/viral detection kit and qualitative polymerase chain reaction (PCR) for Legionella pneumophila were negative. However, using deoxyribonucleic acid extracted from formalin-fixed paraffin-embedded lung tissue, PCR amplification of the ssrA gene of congeneric Legionella species yielded positive results. The results suggest that the cause of death was likely due to bacterial pneumonia caused by Legionella species.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by JC virus (JCV) infection. Although recognized as an AIDS complication in the 1980s, PML has emerged as a serious adverse event of immunosuppressive therapies since 2005, particularly disease-modifying drugs (DMDs) for multiple sclerosis (MS). PML can also occur in patients with collagenous diseases receiving steroid therapy or with age-related immunosuppression. In some cases, the etiology of immunosuppression remains unclear. These cases often present with early manifestations of PML, which, while common, are less well recognized, as PML was identified at more advanced stages in AIDS-related cases. Early diagnosis poses difficulty due to unfamiliar magnetic resonance (MR) images and low viral loads in cerebrospinal fluid (CSF), and brain biopsy may be conducted. This review summarizes the PML pathology identified through biopsy. Early cytopathological changes of JCV-infected cells, with the importance of dot-shaped inclusions associated with promyelocytic leukemia nuclear bodies (PML-NBs), are described. The variability of host immune responses, including PML immune reconstitution inflammatory syndrome (PML-IRIS), is addressed. The potential role of immune checkpoint inhibitors (ICIs), such as pembrolizumab, is also explored. Understanding the pathology of early PML helps to optimize diagnostic strategies and therapeutic interventions, ultimately improving prognosis.

Pregnancy-associated breast cancer has been increasing. In this study, we analyzed patients with breast cancer that occurred during pregnancy (PrBC) and compared their genetic profiles with those of patients with breast cancer that did not occur during pregnancy, within 1 year after childbirth nor during lactation (non-PrBC). We performed gene expression analyses of patients with PrBC and non-PrBC using microarrays and qRT-PCR. Microarray analysis showed that 355 genes were upregulated in the luminal-type PrBC group compared to those in the non-PrBC group. The C-X-C motif chemokine ligand 13 (CXCL13) gene was the most upregulated in the PrBC group compared to that in the non-PrBC group, especially in the luminal A-type (p = 0.016). This result was corroborated by the qRT-PCR analysis of microdissected cancer cells (p < 0.001). A negative correlation was observed between CXCL13 and estrogen receptor 1 (ESR1) mRNA expression levels in luminal A-type breast carcinoma (p < 0.001). Our results provide clues for a better understanding of breast cancer pathogenesis during pregnancy.

The liver's unique cellular structure makes it a frequent site for metastatic cancer. In colorectal liver metastasis (CRLM), surgical resection is essential for long-term survival. Histopathological growth patterns (HGPs) in CRLM, including desmoplastic and nondesmoplastic patterns, provide critical prognostic information. Tumor budding (TB) and poorly differentiated clusters (PDCs), indicators of aggressive cancer behavior, are evaluated using standardized histological scoring systems and are linked to epithelial-mesenchymal transition. This study explored the correlation between HGPs, TB, and PDCs in CRLM. Archived data from Thammasat University Hospital, including resected CRLM specimens, were analyzed. This study evaluated 51 CRLM resection specimens treated with preoperative systemic therapy, finding most to be nondesmoplastic with low TB and grade 1 PDC. Desmoplastic growth was significantly more prevalent in cases receiving preoperative chemotherapy than those that did not. Higher 3-year mortality was noted in nondesmoplastic groups and those with higher TB and tumor regression grade (TRG) scores. Significant correlations were observed between HGPs, TB, and PDCs, despite challenges in assessing these parameters due to issues with noncancer cells, extracellular mucin, bile ductular proliferation, and retraction artifacts. This study underscores the prognostic significance of HGPs, TB, PDCs, and TRG scores in CRLM, highlighting the need for precise histopathological evaluation for more accurate prognostic implications.

A 50-year-old male with a pancreatic tail tumor underwent distal pancreatectomy. At 14 and 27 months after the primary surgery, metachronous liver metastases were identified and partial hepatectomies were performed for each. Pathologic findings of the primary pancreatic tumor were heterogeneous, but they essentially categorized into two components based on their cytologic features: (i) clear cell component and (ii) epithelioid cell component. The metastatic hepatic tumor was entirely composed of the epithelioid cell component. SMARCB1 expression was lost by immunohistochemistry and heterozygous deletion of SMARCB1 was identified by fluorescence in situ hybridization for both the primary and metastatic tumors. Targeted DNA sequencing of a metastatic hepatic tumor sample was performed and SMARCB1 loss was identified. Based on the morphologic, immunohistochemical, and molecular analyzes, the present case was difficult to classify into any of the existing entities. SMARCB1 deficiency might play a key role in the tumorigenesis.

An ovarian mucinous cystic tumor where fundic glands were broadly and evenly distributed. All components were FOXA2-positive. The diagnosis is difficult between "mucinous cystadenoma with fundic gland differentiation" and "monodermal cystic teratoma composed of gastric tissue derived from endoderm".

The dual-stratified pathway of endometrial carcinomas (ECs) has long been dominant. However, in 2013, The Cancer Genome Atlas (TCGA) defined four EC subgroups with distinctive prognoses. Inspired by TCGA, in 2018, the Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE) provided four pragmatic molecular classifiers to apply surrogate immunohistochemical markers to TCGA subgroup categorization. These trends prompted the revision of 2020 WHO Classification of Female Genital Tumors, 5th edition (2020 WHO classification), in which four molecular subtypes are recognized: POLE-ultramutated; mismatch repair-deficient; p53-mutant; and no specific molecular profile. In the 2020 WHO classification, the diagnostic algorithm is characterized by prioritizing POLEmut over other molecular abnormalities. Following the 2020 WHO classification, Federation of International Gynecology and Obstetrics (FIGO) proposed a new staging system in 2023. The updated system focuses on diagnostic parameters, such as histological type and grade, lymphovascular space invasion, and molecular alterations. These new histomolecular diagnostic concepts of ECs are being accordingly introduced into the routine pathology practice. For the first time, the 2020 WHO classification includes mesonephric-like adenocarcinoma (MLA) as a novel histological entity, mimicking the conventional mesonephric adenocarcinoma, but is considered of Müllerian ductal origin.