PMC9560545_01
(A) T1-weighted MR image showing the heterogeneous hyperintense solid lesion and the isointense cystic lesion in the right parietal region. (B and C) T2-weighted (B) and FLAIR MR (C) images showing the heterogeneous hyperintense solid and the hyperintense cystic lesions. (D) Head CT showing no calcification in the mass. (E) Gadolinium contrast-enhanced, T1-weighted MR image showing the solid lesion with heterogeneous enhancement and the cystic lesion in the right parietal region. CT: Computed tomography; FLAIR: fluid-attenuated inversion recovery; MR: magnetic resonance
2188-4226-9-0323-g001.jpg
PMC9560545_01_2188-4226-9-0323-g001.jpg
g001
The solid lesion was heterogeneous hyperintense on T1- and T2-weighted images, while the cystic lesion was isointense on T1- and hyperintense on T2-weighted and fluid-attenuated inversion recovery images (Fig. 1A-C). Head computed tomography (CT) revealed no calcification in the mass (Fig. 1D). We, therefore, suspected an extra-axial brain tumor, such as meningioma, and performed a gadolinium contrast-enhanced MRI, which revealed a heterogeneous enhancement of the solid lesion (Fig. 1E).
(A-C) Whole-body iodine contrast-enhanced CT showed an irregularly shaped nodule in the left lung (A; red arrow). The lymph nodes of the pulmonary hilum (B; yellow arrow) and mediastinum (C; orange arrow) were swollen, predominantly on the left side. (D-F) Intraoperative photographs. The brain tumor was adherent to the dura mater (D). The solid lesion was resected after puncturing the cystic lesion (D; white arrow), and the solid lesion (E; pink arrow) was sharply demarcated from the surrounding parenchyma and pia mater (E). Gross total resection was achieved (F). (G) Postoperative MR image showing gross total removal of the lesion. CT: computed tomography; MR: magnetic resonance
2188-4226-9-0323-g002.jpg
PMC9560545_01_2188-4226-9-0323-g002.jpg
g002
This examination revealed an irregularly shaped nodule in the left lung (Fig. 2A) and left pleura, multiple ring-enhancing lesions in the liver, and multiple swollen lymph nodes (LNs) in the left hilum, mediastinum, bilateral axillae, para-aortic region, and mesentery. The hilar and mediastinal LNs were swollen, predominantly on the left side (Fig. 2B and C). The brain tumor adhered to the dura mater (Fig. 2D). The solid lesion was sharply demarcated from the surrounding parenchyma and pia mater (Fig. 2E), and gross total resection was achieved (Fig. 2F). Postoperative MRI showed gross total removal of the tumor (Fig. 2G).
(A) Hematoxylin and eosin staining of the axillary LN specimen revealed the proliferation of atypical cells with a high N/C ratio. (B-D) The tumor cells that metastasized to the axillary LN were positive for CD56 (B), chromogranin A (C), and synaptophysin (D). (E) Immunohistochemical two-antibody cocktail staining (TTF-1/Napsin A) of the tumor cells showed positivity for nuclear TTF-1 but negativity for cytoplasmic Napsin A. LN: lymph node; N/C ratio: nuclear-cytoplasmic ratio
2188-4226-9-0323-g003.jpg
PMC9560545_01_2188-4226-9-0323-g003.jpg
g003
Histopathological examination of the axillary LN revealed proliferation of atypical cells with a high nuclear-to-cytoplasmic ratio (Fig. 3A). Immunohistochemistry showed that the tumor cells were positive for CD56, chromogranin A, synaptophysin, and thyroid transcription factor-1 (TTF-1) (Fig. 3B-E), and negative for Napsin A (Fig. 3E), p40, and CK14 (data not shown), leading to the diagnosis of small cell lung cancer LN metastasis.
(A-D) Histopathological findings of the brain tumor. (A) Gross findings of the excised brain lesion specimen. The tumor lesion was adherent to the dura mater. (B-D) Histopathological findings of the excised brain lesion specimen showing intratumoral hemorrhagic necrosis. There was no tumor invasion into the dura mater (D). *: dura mater;  : arachnoid mater;  : hemorrhagic necrosis
2188-4226-9-0323-g004.jpg
PMC9560545_01_2188-4226-9-0323-g004.jpg
g004
Intriguingly, the metastatic brain tumor was exclusively confined to the arachnoid membrane (Fig. 4A-D), without dural infiltration by metastatic tumor cells, except for very few vessels in the dura mater (Fig. 4D).