Experience Sharing in Pathological Diagnosis of Early Adenocarcinoma of the Lung

Background: In daily work, there are still many pathologists who have difficulty handling the diagnosis of atypical adenomatous hyperplasia, adenocarcinoma in situ, minimally invasive adenocarcinoma, and lepidic adenocarcinoma, and the boundaries are not clear enough. Sometimes, the diagnosis is difficult, and there is sometimes poor reproducibility between different pathologists. Accurate diagnosis and differential diagnosis require a certain amount of experience. Methods: During the COVID-19 pandemic, we collected a large number (n = 381) of specimens of early lung adenocarcinoma, most of which (n = 356) were solitary lesions and 25 were multifocal lesions. There were 78 nodules in multifocal lesions, total 434 nodules. We summarized very careful microscopic observation and comparative analysis on all frozen and paraffin sections collected from many early lung adenocarcinoma specimens, continuously summarizing our experience. Results: Based on the World Health Organization's 2021 classification and diagnostic criteria for lung adenocarcinoma, new perspectives have been proposed on how to distinguish between atypical adenomatous hyperplasia, adenocarcinoma in situ, minimally invasive adenocarcinoma, and lepidic adenocarcinoma. In particular, new perspectives have been proposed on how to identify invasive aspects, and there are also some new perspectives on early lung mucinous lesions. Conclusion: Atypical adenomatous hyperplasia, adenocarcinoma in situ, minimally invasive adenocarcinoma, and lepidic adenocarcinoma all have corresponding morphological diagnostic criteria, but the morphological boundaries are sometimes not easy to determine and require some experience accumulation. The intraoperative frozen pathological diagnosis of early adenocarcinoma of the lung needs to be closely combined with imaging examination, and has very rich morphological experience.

Lepidic-Type Lung Adenocarcinomas: Is It Safe to Observe for Growth Prior to Treating?

BACKGROUND

Lepidic-type adenocarcinomas (LPA) can be multi-focal, and treatment is often deferred until there is observed growth. This study investigated the potential downside of that strategy by evaluating the relationship of nodal involvement with tumor size and survival.

METHODS

The impact of tumor size on lymph node involvement and survival was evaluated for National Cancer Database patients who received surgery without induction therapy as primary treatment for cT1-3N0M0 histologically confirmed LPA from 2006-2019 using logistic regression, Kaplan-Meier, and Cox analyses.

RESULTS

Positive nodes occurred in 442 (5.3%) of 8,286 patients. The incidence of having positive nodes approximately doubled with each 1cm increment increase in size. Patients with positive nodes were more likely to have larger tumors (27mm vs 20mm,p<0.001) and clinical T2+ disease (40.7% vs 26.8%,p<0.001) compared to node-negative patients, but tumor size was the only significant independent predictor of having positive nodal disease in logistic regression analysis; this association grew stronger with each incremental centimeter increase in size. Patients with positive nodes were more likely to undergo adjuvant radiation (23.5% vs 1.1%,p<0.001) and chemotherapy (72.9% vs 7.9%,p<0.001), and expectedly had worse survival compared to the node negative group in univariate (5-year overall survival 50.9% vs 81.1%,p<0.001) and multivariable (Hazard ratio 2.56 [95% CI 2.14-3.05],p<0.001) analyses.

CONCLUSIONS

Nodal involvement is relatively uncommon in early-stage LPAs but steadily increases with tumor size and is associated with dramatically worse survival. This data can be used to inform treatment decisions when evaluating LPA patients.

Complete Lymphadenectomy for Clinical Stage I Lepidic Adenocarcinoma of the Lung: Is it justified?

The role of a systematic lymphadenectomy in patients undergoing surgery for clinical stage I lung lepidic adenocarcinoma is still unclear. In the last years, some authors have advocated the possibility to avoid a complete lymph-node dissection in this setting. Results of patients who received systematic hilar-mediastinal nodal dissection for this oncologic condition are here reported. Between 2012 and March 2019, 135 consecutive patients underwent lung resection for clinical stage I lepidic adenocarcinoma, at our institution. Only patients (n=98) undergoing lobectomy or sublobar resection associated with systematic hilar-mediastinal nodal dissection were retrospectively enrolled in the study. Patients' mean age was 67.8±8.7 years (range 37-84). Three were 52 females and 46 males. Resection was lobectomy in 77.6% (n=76) and sublobar in 22.4% (n=22). All the resections were complete (R0). Histology was lepidic predominant adenocarcinoma in 85 cases and minimally invasive adenocarcinoma in 13 cases. At pathologic examination, N0 was confirmed in 78 patients (79.6%), while N+ was found in 20 cases (20.4%), (N1 in 12, 12.2% and N2 in 8, 8.2%). No mortality occurred. Complication rate was 8.2%. At a median follow-up of 45.5 months, recurrence rate was 26.5%. Disease-free 5-year survival was 98.6% for stage I, 75% for stage II and 45% for stage III, p<0.001. A complete nodal dissection can reveal occult nodal metastases in lepidic adenocarcinoma patients and can increase the accuracy of pathologic staging. N1/N2 disease is a negative prognostic factor for this histology. A systematic lymph-node dissection should be considered even in this setting.

A severe combined immunodeficiency disease mouse model of human adenocarcinoma with lepidic-predominant growth

Severe combined immunodeficiency disease (SCID) mice with human lepidic adenocarcinoma were established by the intrabronchial implantation of fresh surgically resected specimens. Human pulmonary adenocarcinoma tissue from 16 different cases was transplanted into SCID mice, and SCID mouse tumors were established from four of these cases (25%). Among the four tumors, the tumor cells of two SCID mice showed replacement lepidic growth of mouse alveolar structures accompanied by multiple intrapulmonary lesions. Human lung carcinoma cell lines showing lepidic growth are rare and the xenograft models using the SCID mouse model developed in the current study will be useful for analyzing the growth and/or progression patterns and clinical behavior of lepidic adenocarcinoma, the major histological subtype of human carcinoma of the lung.

MCM7 expression is correlated with histological subtypes of lung adenocarcinoma and predictive of poor prognosis

Emerging evidence has implicated that the abnormal expression of MCM3 and MCM7 contributes to tumor formation and progression. However, MCM3 and MCM7 protein expression in different subtypes of lung adenocarcinoma have not yet been reported. In the present study, we detected MCM7 and MCM3 protein level in five subtypes of lung adenocarcinoma by immunohistochemistry. The five subtypes can be divided into 3 grades-grade 1: lepidic adenocarcinoma, grade 2: acinar or papillary adenocarcinoma and grade 3: solid or micropapillary adenocarcinoma. The immunostaining showed that MCM7 level was lowest in the grade 1 subtype and highest in the grade 3 subtypes. The statistical analysis proved that MCM7 expression increased step wisely with the ascending of tumor grades. However, there is no significant relationship between MCM3 expression and tumor grades. In addition, we investigated the association of MCM7 and MCM3 expression with clinicopathological characteristics. The results showed that tumors with lymph node metastasis had higher MCM7 level than those without lymph node metastasis statistically (P<0.0001). MCM3 expression has no significant relationship with clinicopathological characteristics. In conclusion, our results suggested that MCM7 may be a useful biomarker for the pathological diagnosis of subtypes of lung adenocarcinoma and it also may be a potential prognostic marker for lung adenocarcinoma.