Desmoplastic small round cell tumor (DSRCT) is a rare soft tissue tumor that generally involves the retroperitoneum, pelvis, omentum and mesentery in younger patients. However, extra-abdominal DSRCT is very rare. A 49-year-old Japanese man noticed a mass in the right parotid gland. Ultrasound examination revealed a solid tumor about 2 cm in diameter. Computed tomography (CT) of the whole body revealed no other tumors or lymph node swelling. Superficial parotidectomy was performed. Histologically, the tumor was composed of various-sized tumor cell nests in an abundant fibromyxoid and collagenous background. The tumor cells were small to medium-sized. Immunohistochemistry showed that the tumor cells were immunoreactive for epithelial markers and desmin. They also showed strong nuclear staining with a Wilms tumor 1 (WT1) antibody detecting the C-terminal region (C-WT1), but not the N-terminal region (N-WT1). We also performed 3′/5′ expression imbalance assay based on reverse transcription polymerase chain reaction (RT-PCR) to determine whether aberrant WT1 gene expression was present. This tumor was found to lack 5′-regional expression of the WT1 gene, as well as immunoreactivity with the N-WT1 antibody. Finally, fluorescence in situ hybridization (FISH) and RT-PCR analyses revealed the presence of a gene showing fusion between exon 7 of EWSR1 and exon 8 of WT1. The tumor was diagnosed as a DSRCT of the right parotid gland. The patient has been followed for 3 years without recurrence or metastasis. Although DSRCT in the salivary gland is extremely rare, it should be included in the differential diagnosis of poorly differentiated salivary gland neoplasms, especially with a fibromyxoid background. Pathologists should bear in mind that DSRCT may occur in major salivary glands and should perform immunohistochemistry with appropriate antibodies, not only those against keratin and desmin, but also one detecting the C-terminal region of WT-1. Furthermore, molecular detection of EWSR1-WT1 fusion gene conclusively confirmed the diagnosis of DSRCT in this uncommon location.

The development of next-generation sequencing (NGS) has enabled the discovery of cancer-specific driver gene alternations, making precision medicine possible. However, accurate genetic testing requires a sufficient amount of tumor cells in the specimen. The evaluation of tumor content ratio (TCR) from hematoxylin and eosin (H&E)-stained images has been found to vary between pathologists, making it an important challenge to obtain an accurate TCR. In this study, three pathologists exhaustively labeled all cells in 41 regions from 41 lung cancer cases as either tumor, non-tumor or indistinguishable, thus establishing a “gold standard” TCR. We then compared the accuracy of the TCR estimated by 13 pathologists based on visual assessment and the TCR calculated by an AI model that we have developed. It is a compact and fast model that follows a fully convolutional neural network architecture and produces cell detection maps which can be efficiently post-processed to obtain tumor and non-tumor cell counts from which TCR is calculated. Its raw cell detection accuracy is 92% while its classification accuracy is 84%. The results show that the error between the gold standard TCR and the AI calculation was significantly smaller than that between the gold standard TCR and the pathologist’s visual assessment ($p<0.05$). Additionally, the robustness of AI models across institutions is a key issue and we demonstrate that the variation in AI was smaller than that in the average of pathologists when evaluated by institution. These findings suggest that the accuracy of tumor cellularity assessments in clinical workflows is significantly improved by the introduction of robust AI models, leading to more efficient genetic testing and ultimately to better patient outcomes.

The incidence of axillary lymph node metastasis (ALNM) of colon cancer is very low, and there have been only a few reports of solitary ALNM. Neither the mechanism involved in solitary colon cancer ALNM nor the proper treatment has been elucidated. We encountered a case of solitary left ALNM after curative resection of carcinoma at the colostomy site. A 53-year-old man underwent a Hartmann’s operation for Hirschsprung disease during his adolescence. He complained of a mass of the descending colon and was diagnosed with colon cancer at the colostomy site with pagetoid spread to the adjacent skin. The cancer at the stoma site was resected, and a transverse colostomy was performed. Nine years later, his carbohydrate antigen (CA) 19-9 level was high during a health screening. On physical examination, adenopathy was palpated in the left axilla. Computed tomography (CT) demonstrated a lymph node in the left axillary fossa that was 33 mm in diameter, and 18F-fluorodeoxyglucose positron emission tomography/CT showed high uptake in the lesion. We performed a curative resection of the left axillary lymph node. The lesion was pathologically diagnosed as left ALNM originating from the adenocarcinoma at the colostomy site. After lymph node resection, his serum CA19-9 level decreased compared to that observed at baseline. He has been receiving adjuvant chemotherapy (capecitabine plus oxaliplatin) without recurrence for 5 months after lymph node resection. The present case report shows that carcinoma at the colostomy site with pagetoid spread can metastasize to the axillary lymph nodes through superficial abdominal lymphatic pathways, and surgical resection followed by adjuvant chemotherapy may be a potent strategy to treat solitary colon cancer ALNM.

Pleuropulmonary blastoma (PPB) is a rare malignant mesenchymal tumor. It is classified into 3 subgroups, and PPB type 1 is known to be a cystic lesion with good prognosis. Here, we report a case of PPB type 1 seen in a 1-year-old girl whose pulmonary cystic lesion had been followed-up as a congenital pulmonary airway malformation since neonate. The cyst had been diagnosed as congenital pulmonary airway malformation before surgery but the final diagnosis was type 1 PPB. The tumor had a somatic mutation in exon 25 of the DICER 1 gene whereas no germline mutation was found

Kidney transplant recipients are immunocompromised hosts at risk for comorbidity and mortality due to infection. Currently, there are no established guidelines for the management of immunosuppressed transplant recipients with coronavirus disease 2019 (COVID-19). The impact of COVID-19 and its therapeutic management on chronic active antibody-mediated rejection (CAAMR) are still unclear. Here, we report a case of CAAMR exacerbation with endarteritis and intimal fibrosis after COVID-19. A 41-year-old female kidney transplant recipient with CAAMR was admitted to a local hospital with moderately severe COVID-19. Her doses of tacrolimus and mycophenolate mofetil were reduced, and she was administered methylprednisolone pulse and antiviral drugs. This resulted in a good clinical course and she was discharged in 15 days. During and after hospitalization, the immunosuppressants were gradually returned to the baseline levels. However, about 1.5 months after discharge, the serum creatinine level became elevated. An indication kidney biopsy showed CAAMR with intimal fibrosis and endarteritis in all interlobular arteries. An increase of immunosuppressant led to a decrease of the serum creatinine level. Factors contributing to CAAMR with intimal fibrosis and endarteritis may include (1) insufficient immunosuppression due to changes in the levels of immunosuppressive; (2) overlap with endothelial cell injury caused by COVID-19, and (3) an immune-activated state associated with COVID-19. COVID-19 is a life-threatening disease that can result in unexpected changes in immunological status. Possible allograft rejection should be carefully managed in such patients.