Orbital granular cell tumours: clinical and pathologic characteristics of six cases and literature review

Objective To retrospectively assess the clinicopathological characteristics of orbital granular cell tumours (GCTs). Methods A non-comparative review of the clinical characteristics, imaging, histopathological features, management, and prognosis of five cases of benign GCT and one case of malignant GCT (MGCT) was conducted, along with a review of the English language literature. Results Among the six cases, four tumours were adherent to the extraocular muscle (EOM), and three tumours to the optic nerve (ON). Morphologic examinations revealed polygonal cells containing periodic-acid-Schiff-positive eosinophilic granules. All tumours (100%) were positive for VIM and NSE, five (83.3%) tumours were positive for S-100, and three (50%) tumours were positive for CD68. The follow-up examination of the MGCT witnessed recurrence and brain metastasis despite several thorough resections, but the patient remained alive; the follow-up examination of the four benign GCTs that had received incomplete excision revealed recurrence in one patient and dramatic shrinkage of the residual tumour in another; there was no recurrence in the other two patients. Conclusions GCT should be considered in the differential diagnosis of orbital tumours, which may affect EOMs and ON. The natural course of GCT can include tumour progression, stability, or spontaneous regression. To avoid recurrence, complete resection is recommended for orbital GCT. To the best of our knowledge, primary orbital MGCT is reported for the first time.