Primary carcinoid tumor of the orbit. A clinicopathologic study with histochemical and electron microscopic observations

Diagnostic and Therapeutic Management of Primary Orbital Neuroendocrine Tumors (NETs): Systematic Literature Review and Clinical Case Presentation

BACKGROUND

The ocular involvement of neuroendocrine neoplasms (NENs) is uncommon and mainly represented by metastases from gastrointestinal and lung neuroendocrine tumors. Primary orbital NENs are even less common and their diagnostic and therapeutic management is a challenge.

METHODS

A systematic review of the literature was conducted from 1966 to September 2023 on PubMed to identify articles on orbital NENs and to summarize their clinical-pathological features, diagnosis and therapeutic management. Furthermore, we presented a case of a locally advanced retro-orbital primary neuroendocrine tumor that was referred to the certified Center of Excellence of Sant'Andrea Hospital, La Sapienza University of Rome, Italy.

RESULTS

The final analysis included 63 records on orbital NENs and 11 records focused on primary orbital NENs. The localization was mostly unilateral and in the right orbit; proptosis or exophthalmos represented the initial symptoms. The diagnostic work-up and therapeutic management was discussed and a diagnostic algorithm for the suspicion of primary orbital NENs was proposed.

CONCLUSIONS

A multidisciplinary approach is required for the management of primary orbital NENs, emphasizing the importance of early referral to dedicated centers for prompt differential diagnosis, tailored treatment, and an improved quality of life and survival.

Neuroendocrine neoplasms of the orbit: report of three cases and a literature review

Neuroendocrine neoplasms (NENs) originate from neuroendocrine cells, and mainly occur in the gastrointestinal tract and lungs, rarely occurring in the orbit. Here, the clinicopathologic factors, treatments and prognosis of three cases of orbital NENs are described. The mean age of the three patients (two females and one male) was 59 years. Two cases exhibited ocular symptoms, including unilateral proptosis and eyelid mass, while the third case presented systemic symptoms exhibited as Cushing's syndrome. The tumours were surgically resected in all three patients. Immunohistochemistry assays revealed positive expression for pan cytokeratin and epithelial membrane antigen in all cases. Additionally, neural cell adhesion molecule 1 (also known as CD56) and synaptophysin were positive in two cases. The pathological diagnosis for case 1 and 2 was 'neuroendocrine carcinoma' and both patients died three months after diagnosis. Case 3 was diagnosed with a neuroendocrine tumour and the symptoms of Cushing's syndrome gradually improved following surgery. In addition, no recurrence was observed during the four-year follow-up period. These cases demonstrate that orbital neuroendocrine tumours show different clinical manifestations due to the different types. Pathology may clarify the diagnosis, classification and grading, and provide a reference value for treatment and prognosis.

Ocular adnexal manifestations of neuroendocrine neoplasms: a case report and a major review

PURPOSE

To describe a patient with orbital neuroendocrine neoplasm (NEN)/carcinoid tumor and to review the clinical presentation, systemic work-up, histopathologic features, and outcome of all previously reported ocular adnexal (OA) NENs.

METHODS

A systematic literature review. PubMed/MEDLINE and Google Scholar databases were searched for all well-documented cases of OA NENs.

RESULTS

Final analysis yielded 94 patients with OA NENs, 50 females (53%) and 44 (47%) males with an average age of 63 years (range 14-86). Of 91 patients with known information, the most common presenting signs were proptosis (56/91, 61%) and visual disturbances (42/91, 47%), induced by a mass most commonly associated with an extraocular muscle (49/63, 78%). The majority of tumors (88/94, 94%) were metastases, most commonly from the gastrointestinal tract (52/88, 59%). OA NEN metastasis presented following detection of primary tumor in 73/94 (78%) patients (median time to metastasis 36 months, range 0-288 months) and as an initial manifestation of disease in 15/94 (16%) patients (median time to primary detection 18 months, range 1-108 months). Systemic work-up included extra-OA NEN biopsy (37/54, 69%), multimodal imaging (42/54, 78%), and other laboratory studies (32/54, 59%). Resection with or without adjuvant chemotherapy, radiotherapy, and biologics was the most common intervention for OA NENs (36/82, 44%). Of 67 patients with available follow-up, the median survival was 108 months (95% CI 55-161 months) and the absolute 5-year survival rate was 68%.

CONCLUSIONS

OA NENs are almost exclusively metastases and can precede detection of primary tumor by many months, requiring appropriate diagnostic work-up.

Orbital metastasis from neuroendocrine tumour: Case report and literature review

Orbital metastases from neuroendocrine tumour are rare entities. An incidental finding of orbital metastasis originating from neuroendocrine tumour is presented in the context of a comprehensive review of all case reports and series published to date. Demographics, clinical features, diagnostic work-up, treatment and prognostic data from the published literature are discussed. Ninety-five patients with orbital metastases from neuroendocrine tumours have been reported so far. Average age at presentation is 63.8 years (range 25-86), with no significant gender predominance. Gastrointestinal tract is the most common site of primary neuroendocrine tumours (62-85%). Typical presentation includes proptosis (80-85%) and diplopia (27-62%) in patients with known primary neuroendocrine tumour elsewhere. Histological subtype and presence of metastases seem to be important prognostic factors. Incidental finding of neuroendocrine tumour mestastases in asymptomatic patients with unknown primary disease is uncommon. In such cases, orbital biopsy and structural and functional imaging are essential to establish a diagnosis and stage the disease.

Carcinoid Tumors of the Orbit and Ocular Adnexa

PURPOSE

Well-differentiated neuroendocrine or carcinoid tumors are found most commonly in the gastrointestinal tract. When metastatic to the orbit, they tend to have a propensity for the extraocular muscles. The purpose of this study was to better understand the diversity in presentation of orbital carcinoid disease and to determine predictors for survival.

METHODS

In this observational cross-sectional cohort study, data from 8 tertiary orbital practices were compiled. Demographic, clinical, pathologic, American Joint Committee on Cancer stage and grade, imaging, and management data were extracted for all the patients. Descriptive statistics were calculated. Subgroups were compared utilizing analysis of variance analyses and Kaplan-Meier curves. Time to progression and disease-specific and overall mortality were calculated. Comparisons were performed for the following a priori pairs: unknown versus known primary tumor, single versus multiple extraocular muscle involvement, unilateral versus bilateral orbital disease, extraocular muscle versus other orbital involvement, and excisional versus incisional surgery.

RESULTS

A total of 28 patients with carcinoid tumors of the orbit were identified. Of these, 57.1% of patients were female, the mean age at diagnosis of the primary tumor was 58.8 years and the mean age at diagnosis of orbital disease was 62.6 years. At primary presentation, all patients were American Joint Committee on Cancer stage III or IV and 21.4% demonstrated carcinoid syndrome. Muscle involvement was noted in 78.6% of patients, and of these, 72% were noted to have single muscle disease. Eight patients had no primary tumor identified; 3 of these 8 demonstrated disseminated disease at the time of diagnosis. The overall 5-year survival rate was 81.8% from diagnosis of primary tumor and 50% from diagnosis of orbital disease. Subgroup analysis revealed that patients with unilateral orbital disease when compared with bilateral orbital disease had a longer progression-free survival and time to death from all causes (p = 0.025). Patients with disease localized to the orbit at presentation had longer time to death than those with disseminated disease. Treatment with surgery, radiation, or octreotide did not appear to affect survival. Patients managed with systemic chemotherapy had a shorter time of survival than the rest of the group. All other subgroup comparisons were not found to be statistically significant.

CONCLUSIONS

Neuroendocrine tumors of the orbit represent a wide spectrum of disease, with some cases being part of disseminated disease, while others being localized presentations. This heterogeneity may be responsible for the slightly higher overall survival in these patients than others with metastatic carcinoid tumors in other locations.

Clinico-radiological findings of neuroendocrine tumour metastases to the orbit

Purpose: We present the clinico-radiological findings of neuroendocrine tumour metastases to the orbit.Methods: This was a multicentre, retrospective study of patients with neuroendocrine tumour metastases to the orbit. Data was collected from medical records across five different sites within Australia and the United Kingdom.Results: Nine patients (eleven lesions) were identified. The most common presenting complaint was diplopia (5/9, 56%). Disease occurred bilaterally in two patients. Seven patients (78%) had extraocular muscle involvement. The lateral recti (4/9, 44%) and superior recti (2/9, 22%) were the most commonly affected. Ocular presentation preceded primary tumour diagnosis in three patients (33%). On orbital imaging, metastases were most commonly reported as well circumscribed, ovoid or round, heterogeneous, contrast-enhancing masses. Features of intralesional haemorrhage and bony invasion are uncommonly reported.Conclusions: Neuroendocrine tumour metastasis to the orbit is uncommon. Metastases have a propensity for the extraocular muscles, commonly presenting as heterogeneous, well circumscribed, contrast-enhancing lesions on neuroimaging. New ocular symptoms, a history of neuroendocrine tumours, and these radiological findings, should lead to high clinical suspicion of metastatic disease. Atypical findings warrant biopsy to exclude other causes of orbital lesions.

Neuroendocrine tumor metastatic to the orbit treated with radiotherapy

Neuroendocrine tumors are rare neoplasms that infrequently metastasize to the orbit. Given that patients with these tumors may have prolonged survival despite dissemination, maintaining quality of life by providing early diagnosis and effective treatment to preserve vision and comfort is a fundamental issue. We report the case of a 79-year old woman who presented with well-differentiated metastatic neuroendocrine tumor to the liver with no carcinoid syndrome and was started on intramuscular long-acting octreotide with disease stabilization. Two years later she developed right-sided diplopia associated with mild eye discomfort, proptosis and reddening. An magnetic resonance imaging showed a 2.1 cm mass in the right orbit and further biopsy confirmed a neuroendocrine tumor metastasis. The patient was treated with a four-week course of stereotactic radiotherapy to the right orbital metastasis (4000 cGy in 20 fractions) with minor conjunctivitis as the only side effect. Eighteen months later, she remains well with no visual loss.

Orbital carcinoid metastasis: diverse presentations and value of indium-octreotide imaging

PURPOSE

To report two cases of orbital carcinoid metastasis (OCM) with diverse presentations and the role of Indium-Octreotide scan in management of these patients.

METHODS

Clinical, histological and radiological findings and management of the two patients are described. Results are presented.

CONCLUSIONS

We wish to highlight the diversity of presentations in orbital carcinoid. One patient presented with headache, while the other presented with recurrent transient ptosis. To the best of our knowledge, there have been no previous reports of OCM presenting as transient ptosis. The value of Indium-Octreotide scan in detecting the true extent of systemic disease and reducing the need for biopsy in carcinoid tumour is discussed.

A case series of neuroendocrine (carcinoid) tumor metastasis to the orbit

Purpose/Background:

To report the clinical and radiographic features and treatment outcome of neuroendocrine tumor (carcinoid) metastasis to the orbit.

Materials and Methods:

Retrospective chart review of four cases.

Results:

Mean patient age at the time of diagnosis of the primary neuroendocrine tumor and orbital metastasis was 58 and 66 years, respectively, with a mean duration of 8 years between diagnosis of primary tumor and orbital metastasis. Primary neuroendocrine tumor sites were gastrointestinal tract (n = 2), lung (n = 1), and testicle (n = 1). The most common presenting symptom was diplopia (three cases). Magnetic resonance imaging revealed orbital tumor in all cases. Octreotide scan was positive in one case. Treatment was tumor excision in three cases followed by external beam radiotherapy in two cases and one patient was followed without treatment. Tumor cells showed immunoreactivity to chromogranin, synaptophysin, and neuron-specific enolase in all cases. Mean follow-up after orbital tumor diagnosis was 39 months. Three patients had known systemic extraorbital metastasis before orbital involvement (mean interval of 5.9 years) and one case had immediately after development of orbital metastasis. One patient had multiple recurrences of orbital metastasis and eventually underwent exenteration. Two patients died of disseminated metastasis between 2 and 3 years after diagnosis of orbital metastasis.

Conclusion:

All four patients with orbital metastasis from neuroendocine tumor had evidence of systemic extraorbital metastasis. Aggressive metastatic neuroendocine tumors of orbit can lead to local recurrence even after surgical excision and radiation. Imaging tests were helpful in allowing early diagnosis and for monitoring after treatment.

Neuroendocrine tumors of the orbit--clinicopathological findings in 3 more cases of this rare entity and review of the literature

INTRODUCTION

Neuroendocrine orbital tumors are rare occurrences. They are poorly characterized histologically and a spectrum of different cell types exists. This short case series studies the various tumor morphologies as well as the patients' clinical profiles.

METHODS AND MATERIALS

Patients treated and followed up at the Singapore National Eye Centre over a period of 8 years from 1(st) January 2002 to 31(st) December 2009 were identified from the orbital tumor board results. The case notes of patients with the diagnosis of neuroendocrine tumors were analysed, and a review of the literature performed.

RESULTS

Three patients are described in this series. The history, clinical examination findings, imaging findings as well as tumor histology were described. The mean age was 63 years, and 2 patients were male. All presented with proptosis. Only one patient had systemic symptoms on presentation. All patients had surgical excision of the tumor and two had adjuvant radiotherapy of the orbit. Median follow-up period was 3.5 years.

DISCUSSION

Patients with a biopsy-proven diagnosis of orbital neuroendocrine tumors should be monitored even when systemic examination fails to identify peripheral disease. Such examination should always include a full endoscopic gastrointestinal review.

Rare orbitocranial tumour in an adult

A 35-year-old lady presented with recurrent episodes of painful right upper lid swelling and ptosis of 6 months' duration. The symptoms would subside with oral antibiotics and painkillers. She had also been undergoing treatment for 1 year for multiple painful osteolytic lesions in the long bones and axial skeleton for which no definite diagnosis had been made, despite several radiological and serological investigations having been performed. Computed tomographic scan showed a soft tissue lesion in the superolateral part of the right orbit with erosion of the adjacent bone. Lacrimal gland biopsy showed non-specific inflammatory changes. She was referred for full work-up to exclude lymphoma and metastasis. Magnetic resonance imaging revealed an enhancing soft tissue mass in the right anterior cranial fossa eroding the lateral orbital wall and extending into the orbit. Another mass encased the superior sagittal sinus. Bone marrow biopsy showed near total replacement of marrow cells by a round cell tumour. Immunohistochemical studies revealed that the tumour cells expressed neuron specific enolase and chromogranin. The pathological findings suggested a diagnosis of neuroendocrine tumour though neuroblastoma could not be unequivocally ruled out. A(131) I-metaiodobenzylguanidine scan showed no uptake. Radiologic studies suggested multiple bony metastases. No other site of primary tumour was found so there was a strong possibility of it being a primary orbito-cranial neurogenic tumour. Neuroblastomas and neuroendocrine tumours are very rare in adults. The orbit is an unusual site for a primary of this nature. In addition, it is quite difficult to make a specific diagnosis in a less differentiated tumour.

Rare orbitocranial tumour in an adult

A 35-year-old lady presented with recurrent episodes of painful right upper lid swelling and ptosis of 6 months' duration. The symptoms would subside with oral antibiotics and painkillers. She had also been undergoing treatment for one year for multiple painful osteolytic lesions in the long bones and axial skeleton for which no definite diagnosis had been made, despite several radiological and serological investigations having been performed. Computed tomographic scan showed a soft tissue lesion in the superolateral part of the right orbit with erosion of the adjacent bone. Lacrimal gland biopsy showed non-specific inflammatory changes. She was referred for full work-up to exclude lymphoma and metastasis. Magnetic resonance imaging revealed an enhancing soft tissue mass in the right anterior cranial fossa eroding the lateral orbital wall and extending into the orbit. Another mass encased the superior sagittal sinus. Bone marrow biopsy showed near total replacement of marrow cells by a round cell tumour. Immunohistochemical studies revealed that the tumour cells expressed neuron specific enolase and chromogranin. The pathological findings suggested a diagnosis of neuroendocrine tumour though neuroblastoma could not be unequivocally ruled out. (131) I-metaiodobenzylguanidine scan showed no uptake. Radiologic studies suggested multiple bony metastases. No other site of primary tumour was found so there was a strong possibility of it being a primary orbito-cranial neurogenic tumour. Neuroblastomas and neuroendocrine tumours are very rare in adults. The orbit is an unusual site for a primary of this nature. In addition, it is quite difficult to make a specific diagnosis in a less differentiated tumour.

Orbital carcinoid metastases

OBJECTIVE

To describe a series of patients with metastatic orbital carcinoid tumors.

DESIGN

Retrospective case series and literature review.

PARTICIPANTS AND METHODS

Patients were identified from the orbital database and pathology records at Moorfields Eye Hospital. Records were evaluated for age at presentation, race, gender, laterality, visual function and clinical features, site of orbital metastasis, treatment, and outcome. The site of the primary tumor, presence of systemic symptoms, diagnosis and treatment of the primary tumor, and current survival status were also noted.

MAIN OUTCOME MEASURES

Time from tumor to death.

RESULTS

Thirteen patients (9 male) had an average age at biopsy-proven diagnosis of 65.3 years. The primary tumor was ileal in 7, colonic in 4, and from bronchus and breast (1 each); in 9 patients, the primary tumor was already known. Eleven of the 13 patients had noted a mass, 8 had diplopia, 3 had reduced vision, and only 2 had orbital pain. One patient presented with visual hallucinations. Imaging showed single muscle enlargement in 7 patients, a discrete mass in 5, and diffuse fat infiltration in 1 patient. Six patients underwent a meta-iodobenzyl guanidine/octreotide scan and metastatic disease was found in 4. Four patients underwent exenteration, 5 had radiotherapy after tumor debulking, 2 had radiotherapy alone, and 2 patients had local radiotherapy with receptor-targeted chemotherapy. Seven patients died from metastatic tumor. Kaplan-Meier analysis showed a 5-year survival rate of 72% and a 10-year survival rate of 38%. Comparison of the current series with other published series shows a significant difference (improvement) in survival at 5 years (P = 0.027) but not at 10 years (P = 0.08).

CONCLUSIONS

The largest published series of orbital carcinoid tumors is presented, there being a recent trend towards less aggressive surgical management and probably a greater survival rate.

Carcinoid tumour metastatic to the orbit with infiltration to the extraocular orbital muscle. Case report

Ninety-three percent of symptomatic patients with small intestinal carcinoid tumours have metastases. The most common sites of metastases are lymph nodes and liver. Orbital metastases have rarely been described and the majority of them involve the choroid rather than extraocular orbital structures. We report a patient who developed proptosis, impairment of vision and reduced ocular motility on the left side, eighteen months after operation for primary intestinal carcinoid tumour with hepatic metastases. CT and MR studies revealed the tumour mass infiltrating the inferior rectus muscle. Biopsy examined by imprint and frozen section showed tumour consistent with metastatic carcinoid. The tumour was removed. HE and staining for cytokeratin, chromogranin, NSE, serotonin, somatostatin and gastrin showed that the tumour tissue corresponded to that of the primary intestinal carcinoid tumour. Intramuscular orbital metastasis from a carcinoid tumour is a rare occurrence. Diagnosis may be difficult, especially where no evidence of primary carcinoid tumour is present. Metastatic orbital carcinoid should be suspected in patients with a clinical history of carcinoid tumour and who develop ocular complaints and mass lesion in the orbit. Complete surgical removal of the tumour is important for optimal restitution of vision and eye movements.

Ocular metastases secondary to carcinoid tumors: the utility of imaging with [(123)I]meta-iodobenzylguanidine and [(111)In]DTPA pentetreotide

Ocular metastases from carcinoid tumors are considered rare. They can be the primary presentation of a carcinoid tumor or develop during the course of the disease. The extent of distant metastases from carcinoid tumors correlates with poor prognosis and survival; early detection of metastasis may change the overall management. Radiopharmaceutical-labeled imaging techniques have been widely applied for the detection and localization of such lesions based on isotope uptake by neuroendocrine tumors. Routine application of these imaging modalities may reveal previously unsuspected lesions and may also be used to help stage the disease and to identify patients who may be treated with radiopharmaceuticals. Of 40 patients with carcinoid tumors reviewed in our department since we started routine scanning, we identified 6 (15%) who demonstrated ocular metastases: 5 with obvious lesions and 1 with presumed metastasis according to the results of nucleotide scanning. All 6 were negative on screening with [(123)I]meta-iodobenzylguanidine, whereas 3 of 4 who were screened with [(111)In]octreotide showed positive uptake. All patients responded well to radiotherapy and chemotherapy and did not require surgical treatment. The orbit and its contents appear to be a common site for carcinoid metastasis, and radiopharmaceutical imaging with labeled octreotide is useful in identifying many of these lesions.

Uveal metastasis from carcinoid tumor. Clinical observations in nine cases

BACKGROUND

Carcinoid tumor is a low-grade malignancy that usually arises in the gastrointestinal tract or bronchus and rarely metastasizes to the eye. Metastasis of carcinoid tumor to the uvea can be confused clinically with other primary and metastatic uveal tumors.

METHODS

The authors reviewed the records of 410 consecutive patients with uveal metastases referred to the Ocular Oncology Service at Wills Eye Hospital to identify those in whom carcinoid tumor was the primary neoplasm. The authors evaluated the clinical features of these metastases.

RESULTS

Of 410 consecutive patients with uveal metastases, the primary neoplasm was a carcinoid tumor in 9 (2.2%). There were four men and five women. The mean age at ocular diagnosis was 50 years. In five patients (56%), the primary tumor was undiagnosed at ocular presentation. In the other four patients, the mean time interval from diagnosis of the primary carcinoid tumor to uveal metastasis was 89 months (range, 55-180 months). The site of the primary carcinoid tumor was the bronchus in seven patients, the esophagus in one, and the thymus in one. The site of intraocular metastasis was the choroid in six patients, the ciliary body in two, and the iris in one. All choroidal tumors had a characteristic orange color. Initial ocular treatment included external beam radiotherapy in five patients, plaque radiotherapy in two, argon laser photocoagulation in one, and local resection in one. Ocular tumor control was achieved in each patient. After a mean follow-up of 34 months, four patients (44%) are still alive. Five patients have died, with a mean survival of 34 months (range, 2-104 months) after the diagnosis of uveal metastasis.

CONCLUSIONS

Uveal metastasis from carcinoid tumor is rare and tends to arise from the bronchus. Clinically, it has a distinctive orange color and may be associated with a longer systemic survival, compared with uveal metastasis from other primary sites.

A clinicopathologic study of three carcinoid tumors metastatic to the orbit. Immunohistochemical, ultrastructural, and DNA flow cytometric studies

Three patients with histopathologically proven orbital metastatic lesions from a carcinoid tumor are reported. Computed tomography (CT) disclosed a well-circumscribed orbital mass in two of three cases. Each tumor was studied by both light and electron microscopy as well as immunohistochemistry and DNA flow cytometry. A review of the literature discloses the relatively rare occurrence of carcinoid tumors metastasizing to the eye and orbit. With the exception of one case, the reported metastatic carcinoid tumors to the uvea all developed from primary bronchial carcinoids. In contrast, the vast majority of the reported orbital metastases arose from ileal carcinoids. Immunohistochemical markers such as chromogranin A, synaptophysin, and serotonin have proven to be useful diagnostic tools in evaluating carcinoid tumors. Furthermore, DNA flow cytometry may be of prognostic value in patients with metastatic carcinoid tumor.

Orbital nonchromaffin paraganglioma. A case report and review of the literature

Nonchromaffin paraganglioma (NCP), also called glomus body tumor or chemodectoma, is rarely found in the orbit. The behavior of orbital nonchromaffin paraganglioma may potentially be more aggressive than in other head and neck locations. Diagnosis depends on electron microscopic demonstration of membrane-bound neurosecretory granules. Results of histopathologic study show a well-circumscribed lesion without a true capsule with alveolar or organoid arrangements of epithelioid cells within a reticulin framework with thin-walled blood vessels. Cells are polygonal with round or oval nuclei containing rare mitotic figures and pale-staining cytoplasm. Differential diagnosis includes alveolar soft-part sarcoma, alveolar rhabdomyosarcoma, neuroblastoma, carcinoid, and granular cell tumor. Of 29 previously reported cases of orbital NCP, 16 have been reclassified as alveolar soft-part sarcoma. The authors report a patient with an electron microscopically established orbital NCP, with the history of a contralateral glomus jugulare tumor irradiated 14 years previously.

Primary differentiated neuroblastoma of the orbit

A 49-year-old woman had a 12-year history of a localized left orbital tumor that required five subtotal excisions, orbital radiotherapy, and finally an exenteration. The last procedure was performed after visual function had deteriorated and in order to prevent spread of the tumor into a surrounding compartment. The biopsy specimens from the first four surgeries showed a stroma-free spindle cell tumor with benign cytologic features and no mitotic activity, which exhibited palisading of nuclei, imbrication of delicate cytoplasmic processes (neuropil), true perivascular rosettes with cytoplasmic processes oriented perpendicular to vessel walls, and Wright rosettes. The biopsy after radiotherapy and the exenteration specimen contained more polyhedral (gemistocytoid) tumor cells with abundant eosinophilic cytoplasm and tapering cell processes; nuclear pleomorphism without mitotic activity was also seen. Electron microscopy showed the presence of neurosecretory dense-core granules in the perikaryon region of the tumor cells and in the myriad interweaving cytoplasmic processes (neurites); neither Nissl substance nor synapses were identified. Immunohistochemical staining for neuron-specific enolase was positive, but glial fibrillary acidic protein stained negative. This previously undescribed orbital tumor is interpreted as a primary differentiated neuroblastoma without evidence of ganglion cell differentiation that exhibited locally aggressive behavior. The distinctions between neuroblastic and neuroendocrine tumors are discussed.