PMC10352614_01
Positron emission tomography and computed tomography (PET/CT) and magnetic resonance images (MRI) of lesion and mass. (A-C) PET/CT revealed a mass in right lateral wall of the pharynx, along with lung metastases. (D) MRI showed a soft tissue mass with a size of 7.5 cm x 7.5 cm x 3 cm.
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Positron emission tomography and computed tomography (PET/CT) showed a mass in the right lateral wall of the pharynx, along with lung metastases ( Figures 1A-C ). Figure 1D ). Furthermore, there were multiple lymphadenopathies in bilateral neck region. The timeline of treatment administration from the episode of care was presented in  Supplementary Figure 1 .
Histopathological and Immunohistochemical results of the excisional biopsy. (A) The tumor cells were fusiform, arranged in fascicles or storiform growth patterns (HE, x100). (B) A few mitoses and atypical cells with irregular nuclei were observed (HE, x400). (C, D) Immunohistochemical results showed positive staining for alpha-SMA and Ki-67 with a 40% proliferation index.
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Histological examination showed spindle cells with minimally atypia arranged with fascicular or storiform growth patterns in the fibrous stroma, suggestive of low-grade spindle cell sarcoma ( Figures 2A, B ). Regarding immunohistochemical staining, there is positive result for smooth muscle actin (SMA), but a negative result for caldesmon and desmin, with a Ki-67 index of approximately 40% ( Figures 2C, D ).
The magnetic resonance images (MRI) of the LGMS. (A) In March 2020, new multiple lymphatic metastases were observed. (B) In August 2020, the patient obtained a PR after the combined treatment of pembrolizumab and anlotinib. The patient obtained a PR (C) and CR (D) after the monotherapy of pembrolizumab.
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In March 2020, multiple metastases were observed again in the patient's lymph nodes and lungs ( Figures 3A ,  4A, E ). Based on the new response evaluation criteria in solid tumors (RECIST) guideline (version 1.1), the patient obtained a PR in August 2020 and February 2022, respectively (50% and 67% decrease in the sum of diameters of target lesions, respectively) ( Figures 3B, C ,  4B, C, F, G ). Not until the last follow-up in August 2022, the patients obtained a CR in August 2022 (disappearance of all target lesions) ( Figures 3D ,  4D, H ).
Chest computed tomography (CT) scans. (A, E) In March 2020, multiple metastases of lung and mediastinal window were observed. (B, F) In August 2020, a PR was revealed in the lung and mediastinal window of the patient after the combined treatment of pembrolizumab and anlotinib. The patient obtained a PR (C, G) and CR (D, H) in the lung and mediastinal window after the monotherapy of pembrolizumab.
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In March 2020, multiple metastases were observed again in the patient's lymph nodes and lungs ( Figures 3A ,  4A, E ). Based on the new response evaluation criteria in solid tumors (RECIST) guideline (version 1.1), the patient obtained a PR in August 2020 and February 2022, respectively (50% and 67% decrease in the sum of diameters of target lesions, respectively) ( Figures 3B, C ,  4B, C, F, G ). Not until the last follow-up in August 2022, the patients obtained a CR in August 2022 (disappearance of all target lesions) ( Figures 3D ,  4D, H ).