Photographs demonstrating inferior dystopia (A) and proptosis (B) of the right eye. T1-weighted magnetic resonance imaging demonstrates a 2.6 × 3.5 × 3.3-cm mass (asterisk) that displaces the optic nerve (ON) medially (C), diffusely enhances with gadolinium (D), and encases extraocular muscles (EM) and the ON (E), with no bone destruction seen on a computed tomographic scan (F).
Photomicrographs showing tumor (asterisk) proximal to the optic nerve (ON) (hematoxylin-eosin, original magnification ×25) (A) and infiltrating orbital fat and connective tissue (hematoxylin-eosin, original magnification ×50) (B) containing branching microvascular channels (arrow) and a cracking artifact (CA) (hematoxylin-eosin, original magnification ×100) (C) as well as large glomus cell–lined vascular channels (VC) (hematoxylin-eosin, original magnification ×25) (D). Uniform round eosinophilic glomus cells contain vesiculated nuclei and surround capillary-sized blood vessels (arrows) (hematoxylin-eosin, original magnification ×400) (E) are immunoreactive for cytoplasmic α–smooth muscle actin (immunoperoxidase/hematoxylin counterstain, original magnification ×400) (F), and are immunoreactive for surrounding extracellular type IV collagen (immunoperoxidase/hematoxylin counterstain, original magnification ×400) (G).
Pribila JT, Cornblath WT, Ramocki JM, Marentette LJ, Flint A, Elner VM. Glomus Cell Tumor of the Orbit. Arch Ophthalmol. 2010;128(1):144-146. doi:10.1001/archophthalmol.2009.359
Glomus cell tumors are rare, benign neoplasms of the glomus body, a specialized thermoregulatory arteriovenous structure surrounded by smooth muscle–derived glomus cells and unmyelinated nerves located primarily in the dermis of the digits and palms.1 We describe the unique clinical, radiological, and pathological features of a large orbital glomus cell tumor necessitating exenteration for intractable pain.
A 19-year-old woman developed protrusion and painful burning and throbbing of her right eye in February 2005. Initial biopsy revealed an orbital glomus cell tumor. Visual acuity was 20/30 OU. Pupillary, biomicroscopic, funduscopic, tonometric, and periocular sensory examination results were normal with no identifiable bulbar cause for the pain. There was 3.5 mm of right proptosis (Figure 1A and B) with limited abduction and supraduction. Despite treatment with combinations of clonazepam, nortriptyline hydrochloride, gabapentin, and pregabalin and unchanged results on serial clinical examinations and magnetic resonance imaging, the patient requested tumor removal 24 months after the initial visit owing to nonparoxysmal, intractable pain that limited her daily activities.
A magnetic resonance image prior to exenteration demonstrated a large, irregular, lobulated right orbital mass measuring 2.6 × 3.5 × 3.3 cm isointense to muscle on T1 weighting (Figure 1C) that diffusely enhanced with gadolinium (Figure 1D) and encased the right inferior and lateral rectus muscles anteriorly and all extraocular muscles posteriorly, causing medial deviation of the optic nerve (Figure 1C-E) and proptosis of the right eye
(Figure 1C-E). No bone destruction was evident on computed tomography (Figure 1F).
Transconjunctival biopsy was performed to reconfirm the diagnosis before exenteration. Extensive bleeding was encountered and controlled during the biopsy. Despite good vision, the patient underwent right orbital exenteration using an orbitocranial approach for treatment of intractable pain and to prevent intracranial extension of the tumor given the malignant potential of the tumor, which fell into the category of glomus tumor ofuncertain malignant potential as defined by Folpe et al.2 Since exenteration, she has remained pain-free and without recurrence.
Pathologically, the tumor was composed of sheets and nests of bland cells, nonencapsulated, and diffusely infiltrating. The tumor abutted the optic nerve (Figure 2A) and infiltrated surrounding orbital fat and connective tissue (Figure 2B). In some regions, sheets of cells contained small, branching vascular channels typical of glomus cell tumors (Figure 2C). In other areas, large dilated vascular channels lined by 2 to 3 layers of glomus cells (Figure 2D), typical of glomangiomas, were present. The glomus cells were uniform and round, contained eosinophilic cytoplasm (Figure 2E), and demonstrated prominent nuclear vesiculation, small regular nucleoli, no mitoses, and strong immunoreactivity for cytoplasmic α–smooth muscle actin (Figure 2F) and delicate extracellular matrix rich in type IV collagen (Figure 2G). Numerous artifactual breaks that had occurred during biopsy or processing were visible (Figure 2C).
To our knowledge, only 2 other cases of orbital glomus cell tumors have been reported.3,4 Our case had unique clinical, radiological, histopathological, and management aspects that differed considerably from these other cases.
Unlike previous reports, pain was a critical feature of our patient's symptoms. Numerous substance P–containing, nonmyelinated axons are found within glomus cell tumors, suggesting a potential source for the pain.5 This tumor was considerably larger and more infiltrative than other reported orbital glomus cell tumors. There was significant bleeding during the biopsy, which, while not unexpected given the tumor's vascular nature, differs considerably from a report of an encapsulated orbital glomus cell tumor.3 This suggests that encapsulation or the lack thereof may be an important factor in surgical management.
Histopathologically, this tumor had characteristics of both a glomus cell tumor and glomangioma and contained smooth muscle actin typical of glomus cells. The glomus cells were surrounded by delicate type IV collagen–rich extracellular matrix similar to gastric glomus cell tumors, potentially explaining the tumor's friability.6
Finally, to our knowledge this is the first report documenting magnetic resonance imaging characteristics of an orbital glomus cell tumor: multilobulated, isointense to muscle on T1 weighting, and diffusely enhancing with gadolinium. These features aid in its differentiation from lymphoma, metastatic tumors, and other vascular tumors.
Correspondence: Dr Elner, W. K. Kellogg Eye Center, University of Michigan, 1000 Wall St, Ann Arbor, MI 48105 (email@example.com).
Financial Disclosure: None reported.