Histopathological characteristics and artificial intelligence for predicting tumor mutational burden-high colorectal cancer.

BACKGROUND: Tumor mutational burden-high (TMB-H), which is detected with gene panel testing, is a promising biomarker for immune checkpoint inhibitors (ICIs) in colorectal cancer (CRC). However, in clinical practice, not every patient is tested for TMB-H using gene panel testing. We aimed to identify the histopathological characteristics of TMB-H CRC for efficient selection of patients who should undergo gene panel testing. Moreover, we attempted to develop a convolutional neural network (CNN)-based algorithm to predict TMB-H CRC directly from hematoxylin and eosin (H&E) slides. METHODS: We used two CRC cohorts tested for TMB-H, and whole-slide H&E digital images were obtained from the cohorts. The Japanese CRC (JP-CRC) cohort (N = 201) was evaluated to detect the histopathological characteristics of TMB-H using H&E slides. The JP-CRC cohort and The Cancer Genome Atlas (TCGA) CRC cohort (N = 77) were used to develop a CNN-based TMB-H prediction model from the H&E digital images. RESULTS: Tumor-infiltrating lymphocytes (TILs) were significantly associated with TMB-H CRC (P < 0.001). The area under the curve (AUC) for predicting TMB-H CRC was 0.910. We developed a CNN-based TMB-H prediction model. Validation tests were conducted 10 times using randomly selected slides, and the average AUC for predicting TMB-H slides was 0.934. CONCLUSIONS: TILs, a histopathological characteristic detected with H&E slides, are associated with TMB-H CRC. Our CNN-based model has the potential to predict TMB-H CRC directly from H&E slides, thereby reducing the burden on pathologists. These approaches will provide clinicians with important information about the applications of ICIs at low cost.

SMAD4 alteration associates with invasive-front pathological markers and poor prognosis in colorectal cancer.

AIMS: SMAD4 acts as a tumour suppressor, and the loss of SMAD4 is associated with poor prognosis in colorectal cancer (CRC) patients. Although next-generation sequencing (NGS) enabled us to detect numerous genetic alterations in a single assay, the clinical significance of SMAD4 alteration detected with NGS has not been fully investigated. The aim of this study was to evaluate the clinicopathological characteristics and clinical significance of SMAD4 alteration detected with NGS in CRC. METHODS AND RESULTS: We retrospectively investigated 201 patients with stage I-IV CRC, by using a 415-gene panel. To analyse the relationship between SMAD4 alteration and other clinicopathological characteristics, we evaluated clinicopathological variables, including invasive-front pathological markers: tumour budding, poorly differentiated cluster, and Crohn-like lymphoid reaction. Fifty-six patients (28%) had SMAD4 alteration: 24 and 32 patients had SMAD4 mutation and deletion, respectively. SMAD4 alteration was significantly associated with T category (P = 0.027), N category (P = 0.037), M category (P = 0.028), and invasive-front pathological markers, such as poorly differentiated cluster grade 3 (P = 0.020) and absence of Crohn-like lymphoid reaction (P = 0.004). Immunohistochemistry revealed that SMAD4 alteration was significantly associated with loss of SMAD4 (P = 0.023). In 90 patients with stage I-III disease, SMAD4 alteration was significantly associated with poor prognosis for relapse-free and overall survival (P = 0.047; P = 0.022, respectively). Conversely, in 111 patients with stage IV disease, SMAD4 alteration was not significantly associated with overall survival. CONCLUSION: SMAD4 alteration is associated with invasive-front pathological markers and poor prognosis in stage I-III CRC patients.

Utility of comprehensive genomic sequencing for detecting HER2-positive colorectal cancer.

HER2-targeted therapy is considered effective for KRAS codon 12/13 wild-type, HER2-positive metastatic colorectal cancer (CRC). In general, HER2 status is determined by the use of immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Comprehensive genomic sequencing (CGS) enables the detection of gene mutations and copy number alterations including KRAS mutation and HER2 amplification; however, little is known about the utility of CGS for detecting HER2-positive CRC. To assess its utility, we retrospectively investigated 201 patients with stage I-IV CRC. The HER2 status of the primary site was assessed using IHC and FISH, and HER2 amplification of the primary site was also assessed using CGS, and the findings of these approaches were compared in each patient. CGS successfully detected alterations in 415 genes including KRAS codon 12/13 mutation and HER2 amplification. Fifty-nine (29%) patients had a KRAS codon 12/13 mutation. Ten (5%) patients were diagnosed as HER2 positive because of HER2 IHC 3+, and the same 10 (5%) patients had HER2 amplification evaluated using CGS. The results of HER2 status and HER2 amplification were completely identical in all 201 patients (P < .001). Nine of the 10 HER2-positive patients were KRAS 12/13 wild-type and were considered possible candidates for HER2-targeted therapy. CGS has the same utility as IHC and FISH for detecting HER2-positive patients who are candidates for HER2-targeted therapy, and facilitates precision medicine and tailor-made treatment.

Intrathyroid epithelial thymoma (ITET) and carcinoma showing thymus-like differentiation (CASTLE): CD5-positive neoplasms mimicking squamous cell carcinoma of the thyroid.

Carcinoma of possible thymic epithelial origin may occur within the thyroid gland, which was first reported by Miyauchi et al. as intrathyroid epithelial thymoma (ITET). ITET is a rare tumor comprising about 0.08% of all primary thyroid malignancies. It is a low-grade thyroid carcinoma with squamous cell differentiation whose overall survival rate was found to be 71%. Lymph node metastasis at surgery was found in 40% and hematogenous metastases developed in bones, liver and lungs. This tumor grows within the thyroid gland and invades into the thyroid parenchyma as well as into the extrathyroid structures. It is a well-circumscribed solid tumor with a sharp tumor border, but is not capsulated. After fixation, the cut surface of the tumor is gray-white in color and is a solid tumor with lobulation. Tumor calcification was not detected in our 15 cases. The tumor cells show solid sheets of growth with occasional keratinization without follicular or papillary structures. Lymphocytic infiltration in the stroma is one of the most characteristic features of this tumor. The tumor cells are polygonal epithelial cells with distinct nucleoli and ill-defined cell border. Positive immunoreactivity for CD5 is a key feature to differentiate it from undifferentiated carcinoma, poorly differentiated carcinoma, medullary (C cell) carcinoma and high-grade squamous cell carcinoma (so-called primary squamous cell carcinoma) of the thyroid. Negative immunoreactivity for calcitonin, TTF1 and thyroglobulin, and positive immunoreactivity for p63 and KIT are also helpful for differential diagnosis. Nuclear atypia is mild and mitoses are less frequent, with an intermediate proliferation index (MIB-1 labeling index is usually less than 20%), which are also helpful to differentiate it from high-grade primary squamous cell carcinoma of the thyroid. The tumors in our 15 cases demonstrate 3 histological subtypes: keratinizing squamous cell carcinoma type, non-keratinizing basaloid cell carcinoma (lymphoepithelioma-like) type and neuroendocrine carcinoma type, which correspond to subtypes of the mediastinal thymic carcinomas.

Histologically unique case of combined small cell and squamous cell carcinoma in a polypoid bronchial tumor.

Presented herein is a case of combined small cell and squamous cell carcinoma in a polypoid bronchial tumor, showing a histologically unique progression, in a 76-year-old Japanese man. A bronchofiberscopic examination revealed that the bronchus (left B3) was occluded by the polypoid tumor. Biopsies were performed, and the pathological diagnosis was poorly differentiated squamous cell carcinoma. The patient consequently underwent a left upper lung lobectomy. The surgical specimen was described as a 24 x 8 x 8 mm soft tumor, emanating from the bronchial wall (left B3). Histologically, the tumor had two distinct components: (i) nearly the entire tumor was composed of atypical small round cells, with a high nuclear-cytoplasmic ratio, in the lamina propria, under the basement membrane; and (ii) the surface of the tumor was composed of poorly differentiated squamous cell carcinoma that had proliferated primarily above the basement membrane but there was also some proliferation, seen as island-like formations, below the basement membrane. The histological diagnosis was combined small cell and squamous cell carcinoma. It was suspected that poorly differentiated squamous cell carcinoma, generated in the bronchial epithelium, had caused small cell carcinoma resulting from neuroendocrine differentiation during its invasion into the lamina propria.