Molecular characteristics of multifocal invasive mucinous adenocarcinoma of the lung: Report of a rare case

The Diagnosis of Intrapulmonary Metastasis Multifocal Pulmonary Ground-Glass Nodules Based on Oncogenic Driver Mutation: Two Case Reports and Review of Literature

With the increased use of low-dose computed tomography (LDCT), the detection of multifocal pulmonary ground-glass nodules (GGNs) has increased. According to the current clinical guidelines, multifocal GGNs tend to be treated as the multiple primary early-stage lung adenocarcinoma. However, studies have indicated that parts of multiple GGNs may originate from single nodules via intrapulmonary metastasis (IPM). Such IPM indicates the advanced stages even when the multiple GGNs are present as the early characteristics in pathological assessments. However, no gold standard exists for the differential diagnosis of multiple IPM GGNs. Here, we report two multifocal pulmonary GGNs cases where panel sequencing (672 driver mutation loci) showed that patient 1 (P1) shared two rare epidermal growth factor receptor (EGFR) mutations (primary L747_T751del and primary T790M) in the left upper lobe anterior segment and left lower lobe superior segment, respectively. Patient 2 (P2) shared a low-frequency human epidermal growth factor receptor 2 (HER2) mutation (primary Tyr772_Ala775dup) in two GGNs located in the apicoposterior and superior lingular segment of the left lower lobe (LLL). Oncogenic driver mutations were concordant between primary tumors and metastasis. Thus, shared low-frequency driver mutations in multiple GGNs strongly suggested that IPM existed with a high probability in these patients. Also, tumor cell spread through air spaces (STAS) was identified in pathological sections of the left upper lobe (LUL) nodule of P1, suggesting aerogenous spread may have been an effective pathway for IPM. Our report suggests that oncogenic driver mutations have prominent diagnostic value for IPM. Also, GGN IPM may occur in one lung lobe and between in different lung lobes.

Double-mutant invasive mucinous adenocarcinoma of the lung in a 32-year-old male patient: A case report

BACKGROUND

Invasive mucinous adenocarcinoma of the lung, formerly known as mucinous bronchioloalveolar carcinoma, is a rare category of lung tumors and radiologically characterized by dense pneumonic consolidation, ground-glass opacity, crazy paving, and nodules. However, early pleural effusion is uncommon in this malignancy.

CASE SUMMARY

The case of a 32-year-old male patient who visited our facility with symptoms of cough and gradually aggravated shortness of breath was reported. X-ray examination revealed a massive left hydrothorax. The patient underwent thoracocentesis, and pleural fluid tumor markers, including carcinoembryonic antigen, carbohydrate antigen 19-9, neuron-specific enolase, and cytokeratin 21-1 fragment, were significantly elevated. A similar tendency was observed among the serum tumor markers. After draining the pleural effusion, the patient underwent chest computed tomography, and no obvious mass was found in the lung. Thoracoscopy revealed that the left visceral pleura was covered with nodular, cauliflower-like protrusions of various sizes. These histopathological results suggested cancerous cells, and the immunohistochemical findings were consistent with mucinous adenocarcinoma of pulmonary origin. It tested positive for cytokeratin, cytokeratin 5/6, carcinoembryonic antigen, and thyroid transcription factor-1.

CONCLUSION

The patient was diagnosed with a rare case of lung mucinous adenocarcinoma. Subsequent genetic testing was positive for epidermal growth factor receptor-21 mutations and echinoderm microtubule-associated protein-like 4-lymphoma anaplastic kinase fusion. This prompted treatment with alfatinib and crizotinib.

Annexin A2 Expression in the Aerogenous Spread of Pulmonary Invasive Mucinous Adenocarcinoma with Gastric Lineage

Spread through air spaces (STAS) is a unique form of lung cancer progression associated with a worse prognosis. However, the mechanisms underlying STAS and the associated proteins remain unclear. Annexin A2 (ANX A2), which is a membrane-binding protein involved in cell adhesion, is known to promote cancer invasion. In this report, we describe the immunohistochemical analysis of ANX A2 expression in an invasive mucinous adenocarcinoma (IMAC) resected from a 63-year-old man in whom the tumor cells had detached from the alveolar wall and exhibited STAS. At the detachment site, we observed cytoplasmic ANX A2 positivity on the basal side and in the exfoliative gap, as well as reduced collagen IV positivity expression. This biomarker pattern suggested an IMAC with gastric lineage. We hypothesize that ANX A2 is secreted from the basal sides of tumor cells and induces tumor cell detachment by degrading the basement membrane. A further comparison of this case with an IMAC with nongastric lineage suggested the following probabilities: (1) ANX A2 likely contributes to STAS in a manner that is dependent on its subcellular localization. (2) Both the subcellular localization of ANX A2 and the detachment site depend on tumor cell characteristics, including the biomarker immunophenotype.