Orbital metastasis of pituitary growth hormone secreting carcinoma causing lateral gaze palsy
A 52-year-old male was initially diagnosed with acromegaly and pituitary tumor in 1996 at a local community hospital. He underwent subtotal resection through a transphenoidal approach at that time. He subsequently had radiographic progression of disease and spikes in his IGF1 level, which were resistant to aggressive medical therapy, prompting stereotactic radiosurgery in 1998, 2000, 2006, and 2008 under the guidance of his first neurosurgeon. The patient transferred his care to another medical center, where he underwent endoscopic debulking operations in 12/08, and 6/09, followed by fractionated stereotactic radiosurgery (Cyberknife) in 08/09. All surgeries were performed endonasally, and no violation of the subarachnoid space occurred during these surgeries.\nIn November 2010, he developed severe, intractable epistaxis due to a ruptured Left Cavernous internal carotid artery (ICA) pseudoaneurysm, and was transferred to our hospital for further management. We had extensive discussions with the patient about his treatment options, specifically in regard to our concerns for leaving an exposed metallic stent sheath in close proximity to the tumor. He agreed to undergo Hunterian Ligation of the Left ICA with Superficial Temporal Artery-Middle Cerebral Artery (STA-MCA) bypass on December 2. He unfortunately developed a subgaleal abscess 3 weeks postoperatively, requiring washout and craniectomy. He returned for follow-up 1 month later with left gaze palsy. He underwent a follow-up brain magnetic resonance imaging (MRI), which showed a new lesion in the left orbit and lateral rectus muscle []. The mass was demonstrated clearly to be a distinct lesion, with a significant distance from the parasellar tumor burden, no intradural extension, and with osseous invasion. Initial radiographic review was described as concerning for radiation-induced meningioma or metastasis from a systemic cancer.\nWe chose to combine resection of the left orbital lesion with a cranioplasty procedure. We first performed an incision starting within the left eyebrow []. We came through the frontalis muscle, exposing the roof of the orbit, and laterally removed the periosteum down to the zygoma. The temporalis muscle was then taken down to expose the lateral wall of the orbit, where infiltrative tumor was directly visualized. We carefully removed the lateral wall of the orbit, skeletonizing the tumor. The borders of the tumor were identified, and the tumor was completely removed. The tumor was completely external to the subarachnoid space, and no spinal fluid was encountered during this surgery. We then opened the previous incision to complete the cranioplasty in a separate procedure. The patient tolerated the procedure very well, and was discharged home on excellent condition. Postoperative imaging showed gross total resection of the metastatic lesion. He also had an excellent cosmetic outcome related to the supraorbital incision, and experienced resolution of his lateral gaze palsy. Postoperative pathology showed pituitary adenoma with atypical features, further described below.\nPreoperative laboratory work-up showed pan-hypopituitarism, with marked elevation of growth hormone and IGF1. The prolactin level was 1.28 (with absent Hook effect), Growth hormone was 126.0, insulin-like growth factor 1 (IGF1) was 907, follicle-stimulating hormone (FSH) was 0.4, luteinizing hormone (LH) was 0.1, Cortisol was 0.3, and adrenocorticotropic hormone (ACTH) was <5. He was receiving replacement therapy for thyroid function, testosterone, and cortisol hormone replacement. Postoperatively, growth hormone dropped to 31.6, IGF1 dropped to 499, and prolactin dropped to 0.3.\nMicroscopic examination of the current biopsy showed sheets of monomorphic cells infiltrating bone marrow between bone trabeculae []. The neoplastic cells had chromophobic or mildly acidophilic cytoplasm, coarse chromatin, and prominent nucleoli. There were occasional mitoses up to 2 per 10 high-powered fields (HPFs). Some of the adenoma cells were weakly to moderately immunopositive for GH. Immunostaining was negative in all adenoma cells for prolactin, FSH, LH, TSH, and ACTH. There were scattered p53-immunopositive nuclei. The Ki-67 labeling index approached 30% in the most densely labeled area. Although the original biopsy was not available for review, the unusual features for pituitary adenoma in the current biopsy including high Ki-67 proliferation index, increased mitotic activity, and p53-positivity are consistent with atypical pituitary adenoma proposed in the literature.