Spindle cell oncocytoma, a misdiagnosed rare entity of the pituitary – A case report with review of literature and special emphasis on the morphological differentials

Spindle cell oncocytoma (SCO) of the pituitary is a rare tumor of the adenohypophysis occurring in the sellar/suprasellar region. This tumor has been recognized as a distinct entity by the WHO Classification of CNS tumor in 2007. Spindle cell oncocytoma of the pituitary gland accounts for 0.1–0.4% of all sellar region tumors and is predominantly seen in the older adult population. This rare entity simulates clinical and radiological features of pituitary adenoma and is often misdiagnosed. Though WHO grade 1, the tumor can recur and have invasive properties. Herein, we report a 61-year-old woman with panhypopituitarism and temporal field cut, clinically and radiologically diagnosed as pituitary macroadenoma, while the histomorphological and immunohistochemistry features helped in arriving at a diagnosis of Spindle Cell Oncocytoma. The clinicopathological, histomorphological, immunohistochemical, and molecular properties of the tumor are further discussed.

SURG-15. PITUITARY SPINDLE CELL ONCOCYTOMA: A CASE REPORT AND LITERATURE REVIEW

BACKGROUND Spindle cell oncocytoma (SCO) of the pituitary gland is an extremely rare non-functional WHO grade 1 tumor. SCO are often misdiagnosed as nonfunctional pituitary adenomas on pre-operative imaging. They are often hypervascular and locally adherent, which increases hemorrhage risk and limits surgical resection, leading to increased risk of recurrence. We report a case of SCO treated at our institution and provide a review of the current literature. METHODS A 75-year-old male with a history of hypertension, left thalamic stroke, Parkinson’s disease, and normal pressure hypertension presented to neurosurgery clinic with bitemporal hemianopsia, hyponatremia, and abnormal gait and mobility. Imaging showed an enhancing intra- and suprasellar, hyperdense tumor mass measuring 3.0 cm in diameter. We performed a systemic literature search in the PubMed database to identify previous reports of spindle cell oncocytoma. After exclusion of studies that did not meet criteria, 32 publications were selected for critical reading. RESULTS The patient underwent an endoscopic transsphenoidal resection of the tumor via a multi-disciplinary team. The tumor was fibrous and adherent to the intrasellar dura, with gross invasion of the diaphragm sella, necessitating partial resection of the diaphragm. The defect was repaired, and the patient made an uncomplicated recovery. Post-operatively, the patient experienced improved vision. Upon literature review, SCO present in older adults with an average age of 56.2 ± 14.7 with visual deficits (67.9%), headache (33.3%), hypopituitarism (24.7%), and nausea (11.1%). Full resection was achieved in 38.6% of cases leading to recurrence rate of 23.5% with an average time until recurrence of 32.5 months (range 1-120 months). CONCLUSION Careful surgical technique is needed due to SCO hypervascularity and strong adherence to minimize risk of injury to surrounding neurovascular structures. Long-term follow up is recommended due risk of recurrence.

Pituitary spindle cell oncocytoma: illustrative case

BACKGROUND Spindle cell oncocytoma (SCO) of the pituitary gland is an extremely rare nonfunctional World Health Organization grade I tumor. SCOs are often misdiagnosed as nonfunctional pituitary adenomas on the basis of preoperative imaging. They are often hypervascular and locally adherent, which increases hemorrhage risk and limits resection, leading to increased risk of recurrence. The authors report a case of SCO treated at their institution and provide a review of the current literature. OBSERVATIONS SCO of the pituitary gland can be a rare cause of progressively growing pituitary tumors that presents similarly to nonfunctional pituitary adenoma. Endoscopic transsphenoidal resection of the tumor by a multidisciplinary team allowed total resection despite local adherence of the tumor. Postoperatively, the patient’s visual symptoms improved with persistence of secondary adrenal insufficiency and secondary hypothyroidism. LESSONS Careful resection is needed due to SCO’s characteristic hypervascularity and strong adherence to minimize local structure damage. Long-term follow-up is recommended due to the tendency for recurrence.

RARE-21. A RARE CASE OF PEDIATRIC SPINDLE CELL ONCOCYTOMA WITH EML4-ALK FUSION

A 12 year-old male presented with a 2-month history of intermittent headaches, nausea, and vomiting. Magnetic resonance imaging (MRI) of the brain revealed a 2.2 x 3.5 x 2.6 cm lobulated, sellar/suprasellar mass, mildly T1/T2 hyperintense, with mild homogeneous enhancement and diffusion restriction. He underwent transsphenoidal and right craniotomies for gross total resection of the mass. Pathology demonstrated a hypercellular neoplasm with spindled to ovoid tumor cells arranged in fascicles and tight whirls, consistent with a spindle cell oncocytoma. OncoKids, a DNA- and RNA-based next generation sequencing panel, demonstrated an in-frame EML4 exon 2-ALK exon 19 fusion with a total of 179,872 supporting reads. The EML4-ALK fusion gene is predicted to encode a chimeric tyrosine kinase that facilitates multimerization and autophosphorylation of ALK, and activates its downstream targets, such as RAS/ERK, PI3K/AKT, and JAK/STAT pathways. This fusion is found in approximately 5% of patients with non-small cell lung cancer, a subset of inflammatory myofibroblastic tumors, as well as single cases of pulmonary atypical carcinoid, cholangiocarcinoma, and high-grade glioma. However, it has not been previously described in oncocytoma. Chromosomal microarray analysis demonstrated two interstitial non-contiguous deletions in 2p, and an interstitial deletion in 18q that does not include any known cancer-related genes. The deleted segment in 2p23.3p23.2 includes DNMT3A, which mediates DNA methylation and functions in modification of gene expression. DNMT3A mutations are frequent in hematological malignancies, however their role in oncocytoma is currently unknown. The proximal breakpoint of the deletion in 2p23.3p23.2 is in close proximity to but does not reside within ALK. Spindle cell oncocytoma is rarely reported in the pediatric population, with only one case described in the literature. This is the first case report of an oncocytoma with an EML4-ALK fusion. Additional studies are warranted to confirm its functional effect.