PMC8725817_01
MR images previous to first surgery. Sagital (A) and coronal (B) T1-weighted images.
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A subsequent magnetic resonance imaging (MRI) scan of the brain region confirmed a 25-mm pituitary mass lesion extending into both left and right cavernous sinuses (Knosp grade 3) ( Figures 1A, B ).
Pituitary MR images. (A, B) Sagital and coronal T1-weighted postsurgical images. (C, D) Sagital and coronal T1-weighted images, tumor rest growing can be noticed from small capsular rest to 20 mm invasive tumor.
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Postoperative MRI (48 hours after surgery) revealed a tumor remnant (20x7x20 mm) ( Figures 2A, B ). Computed tomography imaging surprisingly showed regrowth of the pituitary mass with a maximum diameter of 36 mm, erosion of the sphenoid bone and invasion of the sinus ( Figures 2C, D ). Nuclear atypia, multinucleation and mitotic figures were frequent (bigger than 2/10 HPF but not specifically quantified in the report).
Histology of the pituitary tumor. (A) Primary tumor showed solid and papillary proliferation of basophilic cells with increased nuclear atypia and mitoses. (B) Ki-67 labeling showed areas with elevated proliferation index. (C) Tumor cells were positive for ACTH. Original magnification x200.
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Histological examination of the previous surgery showed a solid and papillary neoplasm composed of slightly basophilic cells ( Figures 3A-C ).
MR image and histology of the sacral mass. (A) T1-weighted MR image shows a highly invasive sacral metastasis. (B) Tumor metastasis showed solid and papillary proliferation of atypical cells including numerous giant multinucleated cells. (C) Tumor cells were positive for ACTH. Original magnification x200.
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However, the CT scan now showed a mass at S1-S3 level ( Figure 4A ) compatible with metastasis. Histological examination showed a solid and papillary neoplasm positive for ACTH, consistent with metastasis of the primary pituitary tumor ( Figures 4B, C ).
Clinical timeline of case report landmarks in months.
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A clinical timeline is shown in  Figure 5 .