case_images: PMC11371601_01
case_images: Chest CT scans at different time points. The red arrow indicates primary lesion in the left upper lobe of the lung. (A) Chest CT scan of baseline. (B) Chest CT scan of best response PR after first-line treatment with Osimertinib. (C) Chest CT scan showing progression after 24 months of Osimertinib. (D) Chest CT scan showing progression after 4 months of Anlotinib and Aumolertinib. (E) Chest CT scan showing reduction in the LUL lesion after 2 cycles of EP chemotherapy plus Adebrelimab. (F) Chest CT scan showing regression in the LUL lesion after fourth-line treatment with Osimertinib in addition to the existing chemotherapy and immunotherapy regimen. CT, computed tomography; PR, partial response; LUL, left upper lobe; EP, etoposide plus cisplatin.
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case_images: Moreover, pleural thickening and pleural effusion were observed ( Figure 1A ). The patient was diagnosed with stage IV lung adenocarcinoma with EGFR 19del. The patient achieved partial response (PR) after first-line treatment with osimertinib ( Figure 1B ). Subsequently, the patient experienced progressive disease (PD), with an increase in the size of the LUL lesion ( Figure 1C ) and emergence of cervical lymph node metastasis ( Figure 3A ). However, 4 months later, follow-up enhanced CT and neck ultrasonography revealed PD of the LUL lesion ( Figure 1D ) and shrinkage of the cervical lymph nodes ( Figure 3B ). Figure 1E ), while enlargement of the right cervical lymph node was observed ( Figures 3C, D ). Fine-needle aspiration biopsy of the right cervical lymph node was performed to determine the underlying reasons for the inconsistent response in distinct lesions. After two cycles of combined treatment, both the primary LUL lesion and metastatic lesion in the cervical lymph nodes showed a notable decrease ( Figures 1F ,  3E, F ).
case_images: HE and IHC staining of the tumor at different time points. All pictures were taken at a 200-fold magnification using a light microscope. (A) Biopsy specimen of LUL revealed poorly differentiated lung adenocarcinoma with HE staining. (B) The second biopsy of LUL revealed mixed histology of adenocarcinoma and SCLC with HE and IHC staining for TTF-1 and Syn. (C) The third biopsy of the right cervical lymph node revealed poorly differentiated adenocarcinoma with HE and IHC staining for TTF-1 and Syn. HE, hematoxylin and eosin; IHC, immunohistochemistry; LUL, left upper lobe; SCLC, small cell lung cancer; TTF-1, thyroid transcription factor-1; Syn, synaptophysin.
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case_images: Biopsy of the enlarged lesion in the left upper lobe (LUL) revealed poorly differentiated adenocarcinoma of the lung ( Figure 2A ). 14-gene panel testing identified an EGFR 19del mutation ( Immunohistochemical (IHC) staining confirmed the presence of thyroid transcription factor-1 (TTF-1) (weakly +), napsin A (+), synaptophysin (+), CD56 (+), and CgA (+) ( Figure 2B ). Pathological examination revealed poorly differentiated adenocarcinoma originating in the lung ( Figure 2C ).
case_images: The ultrasound features of cervical lymph nodes at different time points. (A) After 24 months of Osimertinib, enlarged lymph nodes were observed in the IV region of the right neck, with a maximum size of 2.3 x 1.7 cm. (B) Following dual-targeted therapy, a previously enlarged lymph node in the IV region of the right neck reduced to 0.5 x 0.5 cm. (C, D) After 2 cycles of EP chemotherapy plus Adebrelimab, increased and enlarged lymph nodes were detected in the right neck IV area, with the largest measuring 1.9 x 1.6 cm and 1.3 x 0.9 cm. (E, F) With the addition of Osimertinib to the existing chemotherapy and immunotherapy regimen, the enlarged lymph nodes in the right neck IV area measured 1.6 x 1.3 cm and 1.1 x 0.8 cm.
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case_images: Subsequently, the patient experienced progressive disease (PD), with an increase in the size of the LUL lesion ( Figure 1C ) and emergence of cervical lymph node metastasis ( Figure 3A ). However, 4 months later, follow-up enhanced CT and neck ultrasonography revealed PD of the LUL lesion ( Figure 1D ) and shrinkage of the cervical lymph nodes ( Figure 3B ). Figure 1E ), while enlargement of the right cervical lymph node was observed ( Figures 3C, D ). Fine-needle aspiration biopsy of the right cervical lymph node was performed to determine the underlying reasons for the inconsistent response in distinct lesions. After two cycles of combined treatment, both the primary LUL lesion and metastatic lesion in the cervical lymph nodes showed a notable decrease ( Figures 1F ,  3E, F ).
case_images: Case presentation of the 68-year-old female patient of SCLC transformation, including timeline, treatment details, chest CT images, neck ultrasound images, HE staining images and NGS findings. CT, computed tomography; HE, hematoxylin and eosin; SCLC, small cell lung cancer; NGS, next-generation sequencing; 19del, exon19 deletion; IHC, immunohistochemistry; TTF-1, thyroid transcription factor-1; Syn, synaptophysin.
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case_images: The flowchart of the treatment process is shown in  Figure 4 .