Lacrimal Sac Tumor: Hemangiopericytoma
ABSTRACT
Purpose:To describe the clinical features and management of a patient with a lacrimal sac hemangiopericytoma .
Methods: Case report .
Results :A sixty nine – years old male presented with right – sided epiphora and swelling in the region of the lacrimal sac.In the lacrimal sac region , there was a solid , palpable mass , not reducible with pressure.In dacryocystography , the sac lumen was normal in size and there was an obstruction at the proximal side of the nasolacrimal duct.Orbital computerized tomography revealed a mass originating from the nasal wall of the lacrimal sac without bony destruction.On surgery , the mass was excised completly and the patency of the lacrimal passage was ensured .The pathologic examination of the mass revealed hemangiopericytoma.
Conclusion:Althoug rare, the diagnosis of a lacrimal sac tumor should always be considered in case of epiphora and swelling in the region of the lacrimal sac.
Key Words: Hemangiopericytoma, lacrimal sac, mesenchymal tumor.
Abstract
A sixty nine-years-old male patient presented to our clinic with right-sided epiphora and swelling in the region of the lacrimal sac. On slit-lamp examination, the size of the tear meniscus was increased and the lacrimal irrigation was negative. In the lacrimal sac region, there was a solid, palpable mass, not reducible with pressure. In dacryocystography, the sac lumen was normal in size and there was an obstruction at the proximal side of the nasolacrimal sac. Orbital computerized tomography revealed a mass originating from the nasal wall of the lacrimal sac without bony destruction. On surgery, the mass was excised completely and the patency of the lacrimal passage was ensured. The pathologic examination of the mass revealed hemangiopericytoma.
Although rare, the diagnosis of a lacrimal sac tumor should always be considered in case of epiphora and swelling in the region of the lacrimal sac.
Key Words: Hemangiopericytoma, lacrimal sac, mesenchymal tumor.
Introducrion
Lacrimal sac tumors are rare tumors of the ocular adnexa characterized by swelling in the region of the lacrimal sac, epiphora, and attacks of acute dacryocystitis (1). In a previous study, only 2 out of 1705 eye and ocular adnexal tumors was found to originate from the lacrimal sac (2). In the ophthalmic literature, lacrimal sac tumors are usually presented as case reports. Lacrimal sac tumors are mainly of epithelial origin and mesenchymal tumors of the lacrimal sac are relatively scarce. Lymphoid and metastatic tumors may also involve the lacrimal sac (1, 3-8). In Table 1, the classification of the tumors of the lacrimal sac is shown.
Case Report
Sixty nine-years-old male patient applied to our clinic with right-sided persistent epiphora and swelling in the lacrimal sac region for a year. The eyelids were in normal positions. In the lacrimal sac region, there was a 10x12 mm mass of rubbery consistency. The mass was not reduced with pressure. The size of the tear meniscus stained with fluorescein was increased. The lacrimal puncta were patent and in normal positions. Fluid irrigated through the puncta revealed patent canaliculi but it did not pass into the nose.
The water soluble non-ionic contrast material was injected through the right upper punctum. The posteroanterior and lateral x-ray films showed a normal sac lumen but a concave contour of the posterior wall of the sac which should normally appear convex. The contrast material did not pass distally beyond the sac-nasolacrimal canal junction.
An orbital computed tomography (CT) was performed for the suspicion of a lacrimal sac tumor. The CT showed a localized, round-shaped mass originating from the nasal wall of the lacrimal sac, growing toward the lumen, without invasion to the nasolacrimal canal, and without bony destruction.
The tumor was assumed to be benign based on the ophthalmic examination and radiologic findings. An external dacryocystorhinostomy with tumor excision was planned. A vertical skin incision of 15 mm, starting 2 mm above the medial canthal ligament and 10 mm nasal to the inner canthus, was performed under local infiltration anesthesia. The lacrimal sac was visualized after dissection of the subcutaneous tissue, orbicularis oculi, and the periosteum. The anterior bundle of the medial canthal ligament was cut. A tamponade soaked in local anesthetic agent and adrenalin was placed in the middle meatus of the nose. A 12x12 mm area of bone was removed with the dental burr. The localization of the lacrimal sac was confirmed with a prob inserted through the upper punctum. The sac lumen was entered with a vertical incision. The mass was easily dissected from the wall of the sac with blunt dissection and en bloc excision of the tumor was performed. The inferior and superior flaps were prepared from the sac and the nasal mucosa and they were anastomosed with 6/0 polyglactin (vicryl) sutures. The wound was closed after the inner canthal ligament was reattached to the periosteum.
The mass was sent for pathologic examination. Grossly, it was a 2 cc mass in dirty white color, with a medium/hard consistency. The mass was stained with hematoxylen-eosin and examined with light microscopy. The tissue was of fibroangiomatous origin, consisting of multiple vessels of various sizes. The thin vessel lumens were filled with erythtrocytes and the vessel walls were hyalinized in some sections. Around the vessels, there were fusiform, poorly delineated cells with oval nuclei, lined in a palisading configuration. In the lumen, there was an inflammatory infiltrate rich in mononuclear cells. The hyalinization was negative with crystal violet amyloid stain. The S-100 protein was also negative showing that the tumor was not of neurologic origin. The pathologic examination was consistent with chronic nonspesific dacryocystitis and hemangiopericytoma.
Discussion
The tumors of the lacrimal sac are relatively rare and two thirds of these tumors are malignant. The clinical symptoms are epiphora, bloody discharge from the puncta and the nose, swelling in the region of the lacrimal sac, and acute dacryocystitis. The benign tumors are not life-threatening as they are not invasive and do not metastize. However, malignant tumors have lethal potential as they metastize and invade the adjacent tissues. Therefore, early diagnosis and treatment is important (1,9).
In reviewing the literature prior to 1994, 375 tumors of the lacrimal sac were reported. Of these cases, 75.6% (232 cases) were of epithelial origin. Of the 75 (24.4%) nonepithelial tumors, 38 (12.3%) were mesenchymal, 16 (5.2%) were melanoma, 18 (5.9%) were reticulosis and malignant melanoma, and 3 (1%) were of neural origin. Of the mesenchymal tumors reported, there were 7 lacrimal sac hemangiopericytomas (10).
The age at onset of hemangiopericytoma is about 45 years. It usually takes origin from the lower extremities, pelvis, and the retroperitoneum. There is no sex predilection. In a case series with 106 patients, the tumor was originating from the lower extremity in 37 cases, and from the retroperitoneum in 26 cases. Although it is a rare occasion, the tumor may also originate from the meninges, nose, paranasal sinuses, and the orbit.(11)
Clinically, the hemangipericytoma is a slow-growing and painless mass. The symptoms depend on the location of the tumor. Orbital hemangiopericytomas cause unilateral-progressive proptosis, decrease in visual acuity, and double vision. The tumors located in the pelvis and the retroperitoneum cause urinary retention, hydroureter, hydronephrosis, abdominal distension, and vomiting. Hypoglycemia has been associated with hemangiopericytomas in the pelvis and the retroperitoneum mediated through production of insulin-like growth factor by the tumor. Hemangiopericytomas usually have insulin-like growth factor receptors even in the absence of clinical hypoglycemia. In our case, the blood glucose levels were normal.(11)
Hemangipericytomas do not have a specific radiologic appearance. In CT, they appear as a radiopaque soft tissue mass. In Figure 1, the CT of our case is shown. Cystic changes in hemangiopericytomas are common. Calcification is rare and is confined to large tumors of long duration. Calcification in small tumors should arise the suspicion of malignancy. Angiograms are more specific as these tumors are rich in blood vessels. Because of the dilated arteries, circulation at the arterial phase is fast. The capillary phase reveals a dense and uniform structure and the venous phase shows dilated outflow channels around the tumor.(11)
The tumor diameter varies from 1 to 23 cm. The tumor has a typical vasculature with tightly packed spindle cells with indistinct cytoplasmic borders around the vessels. The vessels are of various dimensions and typically, the dividing sinusoidal vessels have a ‘staghorn’ configuration. There is hyalinization especially around large vessels. Sometimes there are localized spindle cell areas but these cells are never arranged in long bundles or fascicles as in sarcomas. Pericytic cells are arranged in palisades as in neural tumors (Figures 2,3,4).
Hemangiopericytomas have the potential for malignant transformation in 10% to 60% of cases. In a large series, metastases were reported in 17.2% of the cases. In this series, tumor size larger than 5 cm, increased mitotic activity (at least 4 mitoses in each higher magnification area), cellularity, immaturity or pleomorphism, hemorrhage, and necrosis were described as malignancy criteria (11). In our case, the cells did not show atypia or mitosis or any other criterion for malignancy. Therefore, we treated the case as it is benign.
The treatment in benign cases is with local excision. Radiotherapy may be necessary in tumors fullfilling the malignancy criteria. In large tumors, ligation of the feeder artery before surgery, embolization, or preoperative radiotherapy may be considered (11). In our case, only local excision was performed because the size of the tumor was small and there was not any sign of malignancy .
The follow-up period in our patient after the surgery is 2 years. During the follow-up period, there was no tumor recurrence and the lacrimal passages remained patent. However, hemangiopericytomas may recur even after 15 years.(12)
In clinical practice, swelling in the lacrimal sac region and epiphora are usually due to a mucocele. If the canaliculi are patent and the sac content is not very viscous, the sac will reduce with pressure due to discharge of the secretions. The lacrimal sac tumors should be suspected if there is no reflux with pressure and the sac is relatively hard. In this case, the lacrimal system should be evaluated with advanced imaging techniques.
Table 1. The classification of the tumors of the lacrimal sac.
Non-neoplastic masses
Neoplastic masses
Stone
Diverticule
Mucocele of the lacrimal sac
Anterior elongation of the etmoidal mucocele
Dermoid cyst
Granuloma
Pyogenic
Sarcoidosis
Wegener’s granulomatosis
İdiopathic inflammatory pseudotumor
Tuberculosis
Leprosy, etc.
Epithelial tumors
Benign
Papilloma
Adenoma
Pleomorphic adenoma
Oncocytoma
Malignant
Epidermoid carcinoma
Adenocarcinoma
Mucoepidermoid carcinoma
Mesenchymal tumors
Benign
Capillary and cavernous hemangioma
Hemangiopericytoma
Melanoma
Neurilemmoma
Plexiform neurom
Others (Osteoma, fibroma, etc.)
Malignant (Sarcomas)
Lymphoid tumors (Lymphoma, leukemia, etc.)
Metastatic tumors (Eyelids, uvea, paranasal sinuses, etc.)
LEGENDS
Figure 1. The CT appearance of the case. The mass is originating from the lacrimal sac (arrow).
Figure 2. Fusiform cell areas in a palisading configuration among hyalinized small vessels (x100, Hematoxylen eosin).
Figure 3. Section of an unhyalinized, staghorn-like vessel with a flat endothelial lining. There are hyalinized vessels and pericytic cells arranged in palisades around this unhyalinized vessel (x400, Hematoxylen eosin).
Figure 4. The section of the vessel lumens filled with erythrocytes and hyalinized vessel walls. There are spindle cells among the vessels (x400, Hematoxylen eosin).
References
1. Sutula FC. Tumors of the lacrimal gland and sac. In: Townsend DJ, Jacobiec FA, editors. Principles and Practice of Ophthalmology. Philadelphia: WB Saunders Company, 1994: 1952-67.
2. Scat Y, Loitet S, Carre F. Epidemiological study of 1705 malignant tumors of the eye and adnexa. J Fr Ophthalmol 1996; 19: 83-8.
3. Ryan SJ, Font RL. Primary epithelial neoplasms of the lacrimal sac. Am J Ophthalmol 1973; 76: 73-88.
4. Ni C, Wagoner MD, Wang WJ, et al. Mucoepidermoid carcinomas of the lacrimal sac. Arch Ophthalmol 1983; 101: 1572 - 4.
5. Benger RS, Frueh BR. Lacrimal drainage obstruction from lacrimal sac infiltration by lymphocytic neoplasia. Am J Ophthalmol 1986; 101: 242 - 5.
6. Knowles DM, Jacobiec FA. Orbital lymphoid neoplasma. A clinicopathologic study of 60 patients. Cancer 1980; 46: 576 -89.
7. Duguid IM. Malignant melanoma of the lacrimal sac. Br J Ophthalmol 1964; 48: 394 -8.
8. Economides NG, Page RC. Metastatic melanoma of the lacrimal sac. Ann Plast Surg 1985; 15: 244 -6.
9. Pe’er JJ, Stefanyszyn M, Hidayet AA. Nonepithelial tumors of the lacrimal sac. Am J Ophthalmol 1994; 15: 118: 650-8.
10. Charles NC, Palu RN, Jagirdar JS. Hemangiopericytoma of the lacrimal sac. Arch Ophthalmol 1998; 116(12): 1677-80.
11. Weiss SW, Goldblum JR. Perivascular tumors. In: Strauss M, Gery L, editors. Soft tissue tumors. 4th ed, St. Louis, Mosby, 2001; 1001-36.
12. Roth SI, August CZ, Lissner GS, O’Grady RB. Hemangiopericytoma of the lacrimal sac. Ophthalmology 1991; 98: 925-7.
Purpose:To describe the clinical features and management of a patient with a lacrimal sac hemangiopericytoma .
Methods: Case report .
Results :A sixty nine – years old male presented with right – sided epiphora and swelling in the region of the lacrimal sac.In the lacrimal sac region , there was a solid , palpable mass , not reducible with pressure.In dacryocystography , the sac lumen was normal in size and there was an obstruction at the proximal side of the nasolacrimal duct.Orbital computerized tomography revealed a mass originating from the nasal wall of the lacrimal sac without bony destruction.On surgery , the mass was excised completly and the patency of the lacrimal passage was ensured .The pathologic examination of the mass revealed hemangiopericytoma.
Conclusion:Althoug rare, the diagnosis of a lacrimal sac tumor should always be considered in case of epiphora and swelling in the region of the lacrimal sac.
Key Words: Hemangiopericytoma, lacrimal sac, mesenchymal tumor.
Abstract
A sixty nine-years-old male patient presented to our clinic with right-sided epiphora and swelling in the region of the lacrimal sac. On slit-lamp examination, the size of the tear meniscus was increased and the lacrimal irrigation was negative. In the lacrimal sac region, there was a solid, palpable mass, not reducible with pressure. In dacryocystography, the sac lumen was normal in size and there was an obstruction at the proximal side of the nasolacrimal sac. Orbital computerized tomography revealed a mass originating from the nasal wall of the lacrimal sac without bony destruction. On surgery, the mass was excised completely and the patency of the lacrimal passage was ensured. The pathologic examination of the mass revealed hemangiopericytoma.
Although rare, the diagnosis of a lacrimal sac tumor should always be considered in case of epiphora and swelling in the region of the lacrimal sac.
Key Words: Hemangiopericytoma, lacrimal sac, mesenchymal tumor.
Introducrion
Lacrimal sac tumors are rare tumors of the ocular adnexa characterized by swelling in the region of the lacrimal sac, epiphora, and attacks of acute dacryocystitis (1). In a previous study, only 2 out of 1705 eye and ocular adnexal tumors was found to originate from the lacrimal sac (2). In the ophthalmic literature, lacrimal sac tumors are usually presented as case reports. Lacrimal sac tumors are mainly of epithelial origin and mesenchymal tumors of the lacrimal sac are relatively scarce. Lymphoid and metastatic tumors may also involve the lacrimal sac (1, 3-8). In Table 1, the classification of the tumors of the lacrimal sac is shown.
Case Report
Sixty nine-years-old male patient applied to our clinic with right-sided persistent epiphora and swelling in the lacrimal sac region for a year. The eyelids were in normal positions. In the lacrimal sac region, there was a 10x12 mm mass of rubbery consistency. The mass was not reduced with pressure. The size of the tear meniscus stained with fluorescein was increased. The lacrimal puncta were patent and in normal positions. Fluid irrigated through the puncta revealed patent canaliculi but it did not pass into the nose.
The water soluble non-ionic contrast material was injected through the right upper punctum. The posteroanterior and lateral x-ray films showed a normal sac lumen but a concave contour of the posterior wall of the sac which should normally appear convex. The contrast material did not pass distally beyond the sac-nasolacrimal canal junction.
An orbital computed tomography (CT) was performed for the suspicion of a lacrimal sac tumor. The CT showed a localized, round-shaped mass originating from the nasal wall of the lacrimal sac, growing toward the lumen, without invasion to the nasolacrimal canal, and without bony destruction.
The tumor was assumed to be benign based on the ophthalmic examination and radiologic findings. An external dacryocystorhinostomy with tumor excision was planned. A vertical skin incision of 15 mm, starting 2 mm above the medial canthal ligament and 10 mm nasal to the inner canthus, was performed under local infiltration anesthesia. The lacrimal sac was visualized after dissection of the subcutaneous tissue, orbicularis oculi, and the periosteum. The anterior bundle of the medial canthal ligament was cut. A tamponade soaked in local anesthetic agent and adrenalin was placed in the middle meatus of the nose. A 12x12 mm area of bone was removed with the dental burr. The localization of the lacrimal sac was confirmed with a prob inserted through the upper punctum. The sac lumen was entered with a vertical incision. The mass was easily dissected from the wall of the sac with blunt dissection and en bloc excision of the tumor was performed. The inferior and superior flaps were prepared from the sac and the nasal mucosa and they were anastomosed with 6/0 polyglactin (vicryl) sutures. The wound was closed after the inner canthal ligament was reattached to the periosteum.
The mass was sent for pathologic examination. Grossly, it was a 2 cc mass in dirty white color, with a medium/hard consistency. The mass was stained with hematoxylen-eosin and examined with light microscopy. The tissue was of fibroangiomatous origin, consisting of multiple vessels of various sizes. The thin vessel lumens were filled with erythtrocytes and the vessel walls were hyalinized in some sections. Around the vessels, there were fusiform, poorly delineated cells with oval nuclei, lined in a palisading configuration. In the lumen, there was an inflammatory infiltrate rich in mononuclear cells. The hyalinization was negative with crystal violet amyloid stain. The S-100 protein was also negative showing that the tumor was not of neurologic origin. The pathologic examination was consistent with chronic nonspesific dacryocystitis and hemangiopericytoma.
Discussion
The tumors of the lacrimal sac are relatively rare and two thirds of these tumors are malignant. The clinical symptoms are epiphora, bloody discharge from the puncta and the nose, swelling in the region of the lacrimal sac, and acute dacryocystitis. The benign tumors are not life-threatening as they are not invasive and do not metastize. However, malignant tumors have lethal potential as they metastize and invade the adjacent tissues. Therefore, early diagnosis and treatment is important (1,9).
In reviewing the literature prior to 1994, 375 tumors of the lacrimal sac were reported. Of these cases, 75.6% (232 cases) were of epithelial origin. Of the 75 (24.4%) nonepithelial tumors, 38 (12.3%) were mesenchymal, 16 (5.2%) were melanoma, 18 (5.9%) were reticulosis and malignant melanoma, and 3 (1%) were of neural origin. Of the mesenchymal tumors reported, there were 7 lacrimal sac hemangiopericytomas (10).
The age at onset of hemangiopericytoma is about 45 years. It usually takes origin from the lower extremities, pelvis, and the retroperitoneum. There is no sex predilection. In a case series with 106 patients, the tumor was originating from the lower extremity in 37 cases, and from the retroperitoneum in 26 cases. Although it is a rare occasion, the tumor may also originate from the meninges, nose, paranasal sinuses, and the orbit.(11)
Clinically, the hemangipericytoma is a slow-growing and painless mass. The symptoms depend on the location of the tumor. Orbital hemangiopericytomas cause unilateral-progressive proptosis, decrease in visual acuity, and double vision. The tumors located in the pelvis and the retroperitoneum cause urinary retention, hydroureter, hydronephrosis, abdominal distension, and vomiting. Hypoglycemia has been associated with hemangiopericytomas in the pelvis and the retroperitoneum mediated through production of insulin-like growth factor by the tumor. Hemangiopericytomas usually have insulin-like growth factor receptors even in the absence of clinical hypoglycemia. In our case, the blood glucose levels were normal.(11)
Hemangipericytomas do not have a specific radiologic appearance. In CT, they appear as a radiopaque soft tissue mass. In Figure 1, the CT of our case is shown. Cystic changes in hemangiopericytomas are common. Calcification is rare and is confined to large tumors of long duration. Calcification in small tumors should arise the suspicion of malignancy. Angiograms are more specific as these tumors are rich in blood vessels. Because of the dilated arteries, circulation at the arterial phase is fast. The capillary phase reveals a dense and uniform structure and the venous phase shows dilated outflow channels around the tumor.(11)
The tumor diameter varies from 1 to 23 cm. The tumor has a typical vasculature with tightly packed spindle cells with indistinct cytoplasmic borders around the vessels. The vessels are of various dimensions and typically, the dividing sinusoidal vessels have a ‘staghorn’ configuration. There is hyalinization especially around large vessels. Sometimes there are localized spindle cell areas but these cells are never arranged in long bundles or fascicles as in sarcomas. Pericytic cells are arranged in palisades as in neural tumors (Figures 2,3,4).
Hemangiopericytomas have the potential for malignant transformation in 10% to 60% of cases. In a large series, metastases were reported in 17.2% of the cases. In this series, tumor size larger than 5 cm, increased mitotic activity (at least 4 mitoses in each higher magnification area), cellularity, immaturity or pleomorphism, hemorrhage, and necrosis were described as malignancy criteria (11). In our case, the cells did not show atypia or mitosis or any other criterion for malignancy. Therefore, we treated the case as it is benign.
The treatment in benign cases is with local excision. Radiotherapy may be necessary in tumors fullfilling the malignancy criteria. In large tumors, ligation of the feeder artery before surgery, embolization, or preoperative radiotherapy may be considered (11). In our case, only local excision was performed because the size of the tumor was small and there was not any sign of malignancy .
The follow-up period in our patient after the surgery is 2 years. During the follow-up period, there was no tumor recurrence and the lacrimal passages remained patent. However, hemangiopericytomas may recur even after 15 years.(12)
In clinical practice, swelling in the lacrimal sac region and epiphora are usually due to a mucocele. If the canaliculi are patent and the sac content is not very viscous, the sac will reduce with pressure due to discharge of the secretions. The lacrimal sac tumors should be suspected if there is no reflux with pressure and the sac is relatively hard. In this case, the lacrimal system should be evaluated with advanced imaging techniques.
Table 1. The classification of the tumors of the lacrimal sac.
Non-neoplastic masses
Neoplastic masses
Stone
Diverticule
Mucocele of the lacrimal sac
Anterior elongation of the etmoidal mucocele
Dermoid cyst
Granuloma
Pyogenic
Sarcoidosis
Wegener’s granulomatosis
İdiopathic inflammatory pseudotumor
Tuberculosis
Leprosy, etc.
Epithelial tumors
Benign
Papilloma
Adenoma
Pleomorphic adenoma
Oncocytoma
Malignant
Epidermoid carcinoma
Adenocarcinoma
Mucoepidermoid carcinoma
Mesenchymal tumors
Benign
Capillary and cavernous hemangioma
Hemangiopericytoma
Melanoma
Neurilemmoma
Plexiform neurom
Others (Osteoma, fibroma, etc.)
Malignant (Sarcomas)
Lymphoid tumors (Lymphoma, leukemia, etc.)
Metastatic tumors (Eyelids, uvea, paranasal sinuses, etc.)
LEGENDS
Figure 1. The CT appearance of the case. The mass is originating from the lacrimal sac (arrow).
Figure 2. Fusiform cell areas in a palisading configuration among hyalinized small vessels (x100, Hematoxylen eosin).
Figure 3. Section of an unhyalinized, staghorn-like vessel with a flat endothelial lining. There are hyalinized vessels and pericytic cells arranged in palisades around this unhyalinized vessel (x400, Hematoxylen eosin).
Figure 4. The section of the vessel lumens filled with erythrocytes and hyalinized vessel walls. There are spindle cells among the vessels (x400, Hematoxylen eosin).
References
1. Sutula FC. Tumors of the lacrimal gland and sac. In: Townsend DJ, Jacobiec FA, editors. Principles and Practice of Ophthalmology. Philadelphia: WB Saunders Company, 1994: 1952-67.
2. Scat Y, Loitet S, Carre F. Epidemiological study of 1705 malignant tumors of the eye and adnexa. J Fr Ophthalmol 1996; 19: 83-8.
3. Ryan SJ, Font RL. Primary epithelial neoplasms of the lacrimal sac. Am J Ophthalmol 1973; 76: 73-88.
4. Ni C, Wagoner MD, Wang WJ, et al. Mucoepidermoid carcinomas of the lacrimal sac. Arch Ophthalmol 1983; 101: 1572 - 4.
5. Benger RS, Frueh BR. Lacrimal drainage obstruction from lacrimal sac infiltration by lymphocytic neoplasia. Am J Ophthalmol 1986; 101: 242 - 5.
6. Knowles DM, Jacobiec FA. Orbital lymphoid neoplasma. A clinicopathologic study of 60 patients. Cancer 1980; 46: 576 -89.
7. Duguid IM. Malignant melanoma of the lacrimal sac. Br J Ophthalmol 1964; 48: 394 -8.
8. Economides NG, Page RC. Metastatic melanoma of the lacrimal sac. Ann Plast Surg 1985; 15: 244 -6.
9. Pe’er JJ, Stefanyszyn M, Hidayet AA. Nonepithelial tumors of the lacrimal sac. Am J Ophthalmol 1994; 15: 118: 650-8.
10. Charles NC, Palu RN, Jagirdar JS. Hemangiopericytoma of the lacrimal sac. Arch Ophthalmol 1998; 116(12): 1677-80.
11. Weiss SW, Goldblum JR. Perivascular tumors. In: Strauss M, Gery L, editors. Soft tissue tumors. 4th ed, St. Louis, Mosby, 2001; 1001-36.
12. Roth SI, August CZ, Lissner GS, O’Grady RB. Hemangiopericytoma of the lacrimal sac. Ophthalmology 1991; 98: 925-7.
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