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Orbit Histopathology

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Orbit Bone Structure:

There are 7 bones that form the orbit. These are:

  1. sphenoid
  2. frontal
  3. zygomatic
  4. ethmoid
  5. lacrimal
  6. maxilla
  7. palatine

The orbit is a pear shape, with the optic nerve at the stem, and holds approximately 30 cc volume. The entrance to the globe anteriorly is approximately 35 mm high and 45 mm wide. The depth from orbital rim to the orbital apex measures 40-45 mm in adults. The maximum width is 1 cm behind the anterior orbital margin. The orbital cavity contains the globe, nerves, vessels, lacrimal gland, extraocular muscles, tendons, the trochlea, as well as fat and other connective tissue. An increase in the volume of the extraocular structures within the orbit can cause proptosis, which is protrusion of the globe and/or displacement (deviation) of the globe from its normal position.

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Sagittal section of the globe with surrounding orbital tissues

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Axial cut of the orbit, both eyes

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Axial CT of the right and left orbit

The orbital margin is the anterior opening of the globe and has a quadrilateral spine formed by several of the bones that make up the orbit. The roof of the orbit is formed by the orbital plate of the frontal bone and the lesser wing of the sphenoid.  The fossa of the lacrimal gland lies anterolaterally, behind the zygomatic process of the frontal bone.


The orbit is divided into three areas:

Lacrimal gland

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Normal lacrimal gland tissue with cuboidal epithelium lining acini

The lacrimal gland lies in the anterior, superior, temporal quadrant of the orbit.

Tumors of the Lacrimal Gland

Lacrimal gland neoplasia

Lacrimal gland lymphoma

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External photograph of both eyes, with some increased swelling of the right superotemporal orbit with erythema.

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Coronal CT of both orbits, displaying diffuse fullness of both orbits, rather than a discrete mass.

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Low magnification view of lymphoma, showing a tight conglomeration of lymphocytes.

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Immunoperoxidase staining of lymphoma

Nick’s tips:

Contrary to prior knowledge, studies have shown now that 80% of the tumors of the lacrimal gland are lymphoid in nature. By contrast, when the tumor is epithelial-derived, it is more likely to be benign-mixed tumor.

With benign-mixed tumor (pleomorphic adenoma), the key is to remove the tumor completely, because recurrence may develop into malignant-mixed tumor

Pleomorphic Adenoma (Benign mixed tumor)

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External photograph of both eyes, with subtle fullness of the temporal aspect of the left upper lid

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CT of the orbit showing a coin lesion near the left lacrimal gland, suspicious for pleomorphic adenoma

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Low magnification view of benign-mixed tumor

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Higher magnification view of benign-mixed tumor

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Low magnification view of malignant mixed tumor

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Higher magnification view of malignant mixed tumor

Pleomorphic adenoma is the most common epithelial-derived tumor of lacrimal gland


Adenoid cystic carcinoma

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External photograph showing proptosis and inferior displacement due to fullness of left temporal upper-lid

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CT scan of orbit with lesion in superotemporal portion of the left orbit

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Adenoid cystic carcinoma, cribriform pattern eroding into bone

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Higher magnification view of adenoid cystic carcinoma

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Basaloid variety of adenoid cystic carcinoma

Can develop in a pleomorphic adenoma or may arise from lacrimal gland.

    1. Cribriform (“Swiss cheese”), most common
    2. Comedocarcinoma
    3. Sclerosing
    4. Tubular
    5. Basaloid (solid) (5-year survival is 20%)


Nick’s tips:

These tumors are disarmingly benign, and do not appear to show signs of malignancy on histopathologic examination, but can indeed be malignant. These can metastasize, and the basaloid variety is the most severe type of adenoid cystic carcinoma.

Nonspecific orbital inflammation:

(orbital pseudotumor, or idiopathic orbital inflammatory syndrome)

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External photograph of child displaying erythematous lid and swelling of left eye

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Low magnification view of orbital inflammatory syndrome

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Higher magnification view of orbital inflammatory syndrome

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Orbital inflammatory syndrome with diffuse infiltration

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Sclerosing pseudotumor, which represents a progression of orbital inflammatory syndrome


Treatment: Prompt treatment steroids will produce a prompt response.  The late phase is refractory to treatment.

Nick’s tips:

Inflammatory conditions can be distinguished from proliferative lesions by special stains which will stain for clonality of lymphoproliferative lesions (lymphoma).

Cysts of the Orbit

Cysts may be congenital or acquired. There are several different categories

Dermoid Cyst

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Dermoid cyst, gross specimen

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Cross sectional view of dermoid cyst and contents

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Dermoid with hair follicles and dermal appendages

Embryonic epithelial nests entrapped in embryogenesis

Nick’s tips:

During removal, it is recommended to remove the lesion whole, because keratin that spills from the lesion can cause additional inflammation. These can also spontaneously rupture, causing inflammation.


Inflammation can be idiopathic or from a systemic inflammatory disease, infection, or foreign body.

Thyroid Associated Orbitopathy:

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External photograph of patient with thyroid associated orbitopathy

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CT scan displaying enlargement of extraocular muscles

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Autopsy photo of thyroid ophthalmopathy sparing the tendon

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Myxoid degeneration of thyroid eye disease

Most common cause of unilateral + bilateral proptosis in adults

Nick’s tips:

In thyroid ophthalmopathy, the tendon is spared, versus in myositis, the tendon may be affected.


Bacterial infection



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Mucomycosis on GMS stain


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Hyphae of Aspergillus

Allergic fungal sinusitis

Parasitic infections



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Amyloid deposition on H&E stain

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Amyloid deposition on Congo Red stain


Lymphoproliferative Lesions

Lymphoid hyperplasia

Orbital Lymphoma

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External photograph patient with lymphoma, showing fullness of the orbit

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CT of patient with lymphoma

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Diffuse sheet of lymphocytes, indicative of lymphoma

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Lymphoma, which has been stained with immunoperoxidase for B cells

Nick’s Tips: Lymphoma is on one end of the spectrum of inflammatory/ lymphoproliferative disorders, and on the other is idiopathic orbital inflammatory syndrome/pseudotumor. Atypical lymphoid hyperplasia is somewhere in the middle.


Vascular Tumors


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CT of the orbits with a heterogenous extraconal lesion causing explosive proptosis of the right orbit

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Large lymphatic-like space created by lymphangioma

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Lymphoid tissue interspersed with staghorn spaces which are filled with blood

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Higher magnification of smaller staghorn spaces filled with blood

Nick’s tips:

Proptosis may increase suddenly when the child is sick or when there is spontaneous bleeding into a cyst. These lesions are often called chocolate cysts, due to bleeding in larger cystic areas of the lymphangioma. When they are drained, the blood cells may appear chocolate colored. It can be difficult to remove the entire lymphangioma.


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Choroidal folds seen on retinoscopy, potentially due to hyperopia or an intraconal lesion such as a cavernous hemangioma

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MRI of orbits with lesion arising from the intraconal space of the right eye

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Gross specimen of cavernous hemangioma

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Low magnification view of cavernous hemangioma

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Higher magnification view of cavernous hemangioma, showing separation of RBCs and serum in the cavernous spaces (Indicates low flow)

Cavernous hemangioma in adults

Capillary hemangiomas in children lack a capsule and are more cellular

Nick’s tips:  Cavernous hemangioma usually occurs in people in their 20s-30s and is unilateral.

Solitary fibrous tumors


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External photograph with proptosis due to fullness of orbit of the right eye in patient with hemangiopericytoma

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Hemangiopericytoma showing dense cellular pattern with staghorn lesion

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Hemangiopericytoma with irregular staghorn spaces surrounding by proliferating cells

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Staghorn spaces with vascular channels and proliferating stroma/pericytes in hemangiopericytoma

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Hemangiopericytoma displaying nuclear pleomorphism and clumped chromatin

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Nucleoli, clumped chromatin, and pleomorphism indicating malignant hemangiopericytoma

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Reticulin stain of hemangiopericytoma which is useful to distinguish the collagen reticular network, which is created by the pericyte

Fibrous histiocytoma

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Fibrous histiocytoma with Touton giant cell

Solitary fibrous tumors include hemangiopericytoma, fibrous histiocytoma, and giant cell angiofibromas of the orbit.

Nick’s tips:

Sometimes benign appearing lesions can behave aggressively, and the aggressive appearing lesions can behave benignly. It is important to remove these lesions completely if possible as they can return and undergo malignant transformation.


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Proptosis of the right eye

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CT scan displaying large diffuse lesion obliterating contents of the right orbit

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Embryonal type of Rhabdomyosarcoma, spindle and round shaped nuclei with tadpole-like cytoplasm

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Embryonal type of Rhabdomyosarcoma with tadpole appearing cells

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Tadpole appearing cells with cross striations which are characteristic of embryonal rhabdomyosarcoma

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Trichrome stain which shows cross-striations of embryonal rhabdomyosarcoma

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Rhabdomyosarcoma, alveolar variety, with a characteristic septae filled with cells

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Rhabdomyosarcoma with vimentin staining, which indicates muscle-derived tumor

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Muscle-specific actin immunoperoxidase stain of rhabdomyosarcoma showing muscle-derived lesion

Nerve Tumors


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Low magnification view of plexiform neurofibroma showing bundles of fibroblasts and schwann cells

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Higher magnification view of plexiform neurofibroma

Neurofibroma is the most common nerve sheath tumor


Also known as schwannoma

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Neurilemoma of the optic nerve, shown as an intraconal mass on CT

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Neurilemoma, Antoni A form, which is a noted by the spindle-shaped cells which line up in a palisading pattern.

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Neurilemoma, Antoni B form, which has less organized, myxoid appearance


Adipose Tumors

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Low magnification view of lipoma

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Higher magnification view of lipoma

Bony Lesions

Fibrous dysplasia


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Low magnification view of osteoma

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Higher magnification view of osteoma

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Osteogenic sarcoma

Other bone tumors include osteoblastoma, Ewing sarcoma, giant cell tumor, osteogenic sarcoma, chondroma, chondrosarcoma

Metastatic Tumors:

Secondary tumors may invade via direct extension from surrounding structures of the orbit, such as the sinus, brain, and eye.

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Gross photograph of an exenterated eye due to a conjunctival melanoma from the conjunctiva which extended into the orbit. Note the areas of dark tissue consisent with melanoma.

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Melanocytes cells from a melanoma metastatic to the orbit.

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Squamous cell carcinoma metastatic to the orbit.


Ahmad, S. M., Esmaeli, B., at el. (2009). American Joint Committee on Cancer classification predicts outcome of patients with lacrimal gland adenoid cystic carcinoma. Ophthalmology, 116(6), 1210-1215.

Hawkins, D. S., Gupta, A. A., & Rudzinski, E. (2014). What’s new in the Biology and treatment of pediatric rhabdomyosarcoma?. Current opinion in pediatrics, 26(1), 50.

Liu, K., DeAngelo, P., Mahmet, K., Phytides, P., Osborne, L., & Pletcher, B. A. (2010). Cytogenetics of neurofibromas: two case reports and literature review. Cancer genetics and cytogenetics196(1), 93-95.

Pasmant, E., et al. (2010). Differential Expression of ccn1/cyr61, Ccn3/nov, Ccn4/wisp1, and ccn5/wisp2 in Neurofibromatosis Type 1 Tumorigenesis. Journal of Neuropathology & Experimental Neurology69(1), 60-69.

Shan, S. J., & Douglas, R. S. (2014). The pathophysiology of thyroid eye disease. Journal of Neuro-ophthalmology34(2), 177-185.

von Holstein, S. L., Coupland, S. E., et al. (2013). Epithelial tumours of the lacrimal gland: a clinical, histopathological, surgical and oncological survey. Acta ophthalmologica, 91(3), 195-206.

Wallace, Z. S., Khosroshahi, A., et al. (2012). IgG4-related systemic disease as a cause of “idiopathic” orbital inflammation, including orbital myositis, and trigeminal nerve involvement. Survey of ophthalmology57(1), 26-33.

Weis, E., Rootman, et al. (2009). Epithelial lacrimal gland tumors: pathologic classification and current understanding. Archives of Ophthalmology127(8), 1016-1028.