case_images: PMC9870725_01
case_images: Contrast CT and PET-CT. (a) A mass lesion 51 mm in length with an angiogram sign was observed in the lower lobe of the left lung. Peripherally to the same mass, a 47 mm long mass and a significantly enlarged ipsilateral hilar lymph node were observed. (b) A 146 mm long mass was found in the left iliac bone, extending into the pelvic cavity and muscle layer. There was no invasion into the skin or subcutaneous tissue. (c) PET showed abnormal FDG accumulation consistent with a left lung mass, mediastinal and left hilar lymph nodes, and a left iliac mass. No abnormal FDG accumulation was found in other areas. CT, computed tomography; FDG, fluorodeoxyglucose; PET-CT, positron emission tomography.
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case_images: Peripherally, a similar mass and an enlarged ipsilateral hilar lymph node were observed (Figure 1a). A large mass was found in the left iliac bone, extending into the pelvic cavity and muscle layer (Figure 1b). Positron emission tomography-CT and magnetic resonance imaging revealed no other neoplastic lesions (Figure 1c), and this lesion was diagnosed as a primary sebaceous carcinoma of the lung with ipsilateral intrapulmonary and bone metastases.
case_images: Biopsy results for the left iliac mass. (a) Metastasis of a carcinoma species showing enhanced proliferation was confirmed, and the tumor cells had foamy cytoplasm and unevenly distributed nuclei. Hematoxylin-eosin stain, original magnification x200. (b) Immunohistochemical staining was negative for thyroid transcription factor-1 (TTF-1) (original magnification x200), (c) and P40 was also negative (original magnification X200). (d) Gross cystic disease fluid protein-15 (GCDFP-15) and apocrine differentiation marker were negative (original magnification x200), as were GATA binding protein-3 (GATA 3) and mammaglobin androgen receptor. (e) Adipophilin, a marker of sebaceous differentiation, was positive (original magnification x200).
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case_images: A, and p40. Additionally, the apocrine differentiation marker GCDFP-15 was negative, and adipophilin, a marker of sebaceous differentiation, was positive (Figure 2).
case_images: Treatment course. The patient received palliative radiotherapy of 3 Gy per session for a total of 45 Gy to the left iliac tumor for the purpose of pain relief. After radiotherapy, the iliac tumor reduced in size by 25%, from 146.8 to 109.8 mm, while the lung mass tended to increase in size. After the completion of in situ radiotherapy, pembrolizumab was started. Following four courses of pembrolizumab, the primary lung lesion was reduced by 50% from 61.4 to 30.7 mm, and the total tumor size reduced by 30%.
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case_images: After four courses of pembrolizumab, the primary lung tumor, bone tumor, and total tumor counts were reduced by 38, 46, and 30%, respectively (Figure 3).