Papillary adenocarcinoma is defined as carcinoma with a well‐defined papillary or villous structure. Despite sharing clinicopathological and morphological features with tubular adenocarcinomas, papillary adenocarcinomas frequently show microsatellite instability. The present study aimed to clarify the clinicopathological features, molecular classification, and programmed death‐ligand 1 (PD‐L1) expression characteristics of papillary adenocarcinoma, especially tumors with microsatellite instability. We examined the microsatellite status and expression of mucin core proteins and PD‐L1 as well as the clinicopathological features in 40 gastric papillary adenocarcinomas. Surrogate immunohistochemical analysis of p53 and mismatch repair proteins along with Epstein‐Barr virus‐encoded RNA in situ hybridization were performed for molecular classification. Female predominance and frequent microsatellite instability were observed in papillary adenocarcinoma in comparison with tubular adenocarcinoma. The presence of microsatellite instability in papillary adenocarcinoma was significantly correlated with older age, tumor‐infiltrating lymphocytes, and Crohn's‐like lymphoid reactions. Surrogate examination demonstrated that the genomically stable type (17 cases, 42.5%) was the most common, followed by the microsatellite‐unstable type (14 cases, 35%). Among the seven cases showing PD‐L1‐positive expression in tumor cells, four involved carcinomas with microsatellite instability. These results reveal the clinicopathological and molecular characteristics of gastric papillary adenocarcinoma.

Mixed squamous and glandular papilloma (mixed papilloma) of the lung has been reported in fewer than 25 cases in the English literature. Although it is known as a benign tumor, malignant transformation has been reported. Papillary cystic carcinoma is characterized by papillary and cystic growth patterns and has been reported as a subtype of adenocarcinoma, mainly in the salivary glands, breast, and pancreas. In this article, we report a case of adenocarcinoma-papillary cystic pattern arising from mixed papilloma of the lung in a 76-year-old male patient. Chest computed tomography scan revealed an endobronchial mass growing at the right medial segmental bronchus. Middle lobe lobectomy was performed, revealing a 4.9 × 1.9 cm-sized mass that protruded into the bronchus. Microscopically, the tumor showed numerous cysts lined by micropapillary projections. The tumor cells had round and vesicular nuclei with prominent nucleoli, and mitosis was frequent. A limited portion of the tumor consisted of benign mixed papilloma. The tumor showed diffuse immunoreactivity for thyroid transcription factor-1 and strong expression of p16. We investigated the mutational status of cancer-related genes using targeted next-generation sequencing and identified a genetic alteration in the BRAF gene. This is the first case report of papillary cystic carcinoma arising in mixed papilloma of the lung.

Introduction: Papillary adenocarcinoma (PA) of the lung is a specific type of lung cancer characterized as the presence papillary structures in tumor cells. We report a rare subtype of lung adenocarcinoma, papillary adenocarcinoma, to highlight is distinct pathological features as it has therapeutic and prognostic implications compared to other types of lung malignancies. Case: A 72-year-old male current smoker with initial lung cancer screening showed a 3.5 cm right lower mass. He underwent percutaneous CT guided biopsy with results showing malignant cells favoring Non-Small Cell Cancer. Patient sought second opinion a few months after, and a repeat chest CT showed that the primary lesion has enlarged to 5 cm accompanied by 1 cm left paratracheal area (N3 node). Repeat biopsy with Radial EBUS on the mass as well as EBUS guided biopsy on station 4L were consistent with Papillary Adenocarcinoma. Immunohistochemistry (IHC) showed positive results of TTF and Napsin A and negative results for Thyroglobulin. Next Generation Sequencing (NGS) showed no detectable tumor mutation with PDL at 1% and Tissue mutation burden (TMB) to be high. There were no other metastatic lesions in the abdomen, pelvis and brain. Thyroid imaging was normal. Patient was considered to be stage IIIC T3N3M0 – a rare case of papillary adenocarcinoma. Concurrent chemo-radiation was initiated as patient declined any surgical intervention. Discussion: The major subtypes of adenocarcinoma are acinar, papillary, bronchioloalveolar, and solid adenocarcinoma with mucin production. Papillary adenocarcinoma (PA) is a relatively rare subtype of lung adenocarcinoma. This is characterized by papillary structure in the tumor cells. It accounts for 7.4%-12% of the lung adenocarcinomas. The papillary structures must represent more than 75% of the tumor in a pathological study to confirm the diagnosis. PA is common in nonsmokers and is associated with invasive intrapulmonary metastasis and lymph node involvement. Determining the subtype of adenocarcinoma is vital, as it has both prognostic and therapeutic implications. Surgical intervention has been proven to be an optimal treatment which can bring better prognosis. The role of chemotherapy is still controversial.

A wide range of spontaneous tumors of the ovary are reported in a group of 5903 aged female Sprague-Dawley rats of the CD and CFY strains examined since 1978 in this laboratory. The most commonly observed tumor was the tubular adenoma. Others recorded were tubular adenocarcinoma, papillary cystadenoma, papillary cystadenocarcinoma, a Sertoli's cell tumor, benign and malignant granulosa cell tumors, benign thecal cell tumors, and classical mesotheliomas of ovarian origin. A system of classification and nomenclature of the ovarian tumors from this group is advanced.