case_images: PMC11089941_01
case_images: (a) Mucosal melanoma in left maxillary sinus. Tumor cells show epithelioid morphology, with high nuclear-cytoplasmic ratio, round and hyperchromatic nuclei, and brisk mitoses. (b) Prasad's microstage: level III. Tumor cell infiltration in trabecular bone.
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case_images: Therefore, we performed endoscopic left maxillary sinus tumor biopsy, and the pathology revealed that it was malignant melanoma (Figure 1(a)). Prasad's microstage is level III (Figure 1(b)).  
case_images: (a) Magnetic resonance imaging (MRI) before tumor resection. (b) MRI showing rapid tumor regrowth. (c) MRI showing complete tumor remission. (d) Positron emission tomography (PET) scan confirmed tumor remission. (e)-(g) demonstrate the progression and improvement of left orbital protrusion. (h) The tumor can be seen through the left nostril.
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case_images: Next, magnetic resonance imaging (MRI) was performed, which further identified tumor invasion of the adjacent soft tissue and bone (Figure 2(a)). Figure 2 presents the gradual alterations in both imaging and facial appearance before and after treatment. Unfortunately, left orbital swelling and blurred vision were noted gradually (Figure 2(e)). The tumor was approximately 7 cm in size and involved the maxillary sinus, maxilla bone, nasal cavity, orbital floor, cheek region, and masticator space (Figure 2(b)). Before IMRT, apparent progressive left orbital protrusion was observed in 4 weeks (Figure 2(f)), which was now considered pseudoprogression after two cycles of pembrolizumab immunotherapy. At this time, the colossal regrowth tumor could be directly seen through the left nostril (Figure 2(h)). After regular immunotherapy treatment, MRI on the 294th day after radical tumor resection revealed a widening left osteomeatal complex without an apparent mass lesion (Figure 2(c)). Also, the swollen left orbital has improved in appearance (Figure 2(g)). In the latest follow-up examination, a positron emission tomography scan demonstrated no tumor recurrence or metastasis (Figure 2(d) and 3(c)).
case_images: (a) and (b) Bilateral lung metastases. (c) PET scan confirmed tumor remission. (d) and (e) Bilateral lung metastases were ablated.
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case_images: Subsequent cancer workup with chest CT scans demonstrated bilateral lung metastases (Figure 3(a) and (b)). Figure 3 compares the imaging of lung metastasis before and after immunotherapy. Additionally, chest CT showed that the bilateral upper lung metastases were ablated by immunotherapy (Figure 3(d) and (e)).
case_images: Imaging series of tumor pseudoprogression to complete remission.
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case_images: Figure 4 depicts an imaging series showing tumor pseudoprogression to complete remission.