|Year : 2013 | Volume
| Issue : 1 | Page : 9-13
Morphologic patterns of vascular tumors in Benin City, Nigeria: A 12 year retrospective review
DE Obaseki, WO Akhiwu, JU Aligbe, AP Igbe, GI Eze, Gerald D Forae
Department of Morbid Anatomy, University of Benin Teaching Hospital, Benin City, Edo State, Nigeria
|Date of Acceptance||23-Sep-2013|
|Date of Web Publication||14-Feb-2014|
Gerald D Forae
Department of Morbid Anatomy, University of Benin Teaching Hospital, Benin City, Edo State
Source of Support: None, Conflict of Interest: None
Objective: The objective of this study was to determine the frequency, morphological patterns, age and sex and site distribution of vascular tumor in Benin-City, Nigeria. Materials and Methods: The study was a 12 year retrospective analysis of all histologically confirmed vascular tumors seen over a 12 year period at the Pathology Department, University of Benin Teaching Hospital, Benin-City, Nigeria. Results: A total of 162 vascular tumors representing 18.6% of all soft-tissue tumors were analyzed. 136 (83.9%) were benign, 24 (14.7%) were malignant while 2 (1.3%) cases were of borderline malignancy. Hemangioma was the most frequently encountered tumor in this series constituting 71% of all vascular tumors and 84.6% of the benign tumors. Kaposi's sarcoma (KS) was the most common malignant vascular tumor comprising 14.8% of these lesions. The majority of these tumors were located in the head and neck region (39.5%) followed by the upper and lower extremities accounting for 16.7% and 14.2% respectively. Conclusion: This study has shown that hemangioma is the most predominant vascular tumor and that KS is the most common malignant vascular tumor in this setting. This is similar to previous reports from other researchers locally and internationally.
Keywords: Benign, hemangioma, Kaposi′s sarcoma, malignant, vascular tumors
|How to cite this article:|
Obaseki D E, Akhiwu W O, Aligbe J U, Igbe A P, Eze G I, Forae GD. Morphologic patterns of vascular tumors in Benin City, Nigeria: A 12 year retrospective review. Niger J Surg Sci 2013;23:9-13
|How to cite this URL:|
Obaseki D E, Akhiwu W O, Aligbe J U, Igbe A P, Eze G I, Forae GD. Morphologic patterns of vascular tumors in Benin City, Nigeria: A 12 year retrospective review. Niger J Surg Sci [serial online] 2013 [cited 2021 Apr 12];23:9-13. Available from: https://www.njssjournal.org/text.asp?2013/23/1/9/127099
| Introduction|| |
Tumors of blood vessels form one of the most difficult nomenclatures of oncology as substantiated by the bewildering variety of classifications, which are encountered in the literatures. These varieties of vascular tumors range from benign forms (hemangiomas, lymphangiomas); to borderline forms of unpredictable behavior (hemangiopericytoma and hemangioendothelioma); to malignant forms (angiosarcoma and Kaposi's sarcoma [KS]).  These tumors ranked high in the series of soft-tissue constituting 25% of all soft-tissue tumors in the work done by Coffin and Dehner  in the United States and 27.3% of all soft-tissue tumors in infants and children in Lagos, Nigeria. 
It can thus be acknowledged that vascular tumors form an important group of lesions that deserve extensive study especially with their association in the midst of environmental predisposing factors such as acquired immunodeficiency syndrome (AIDS), post-mastectomy lymph-edema and chronic filarial lymph-edema. Despite this, there are very few reports on vascular tumors in Nigeria. Apart from the work done by Rafindadi  in Zaria, Northern Nigeria, there are invariably scarcity of reports on the comprehensive overview of vascular tumors in other parts of Nigeria. However, the series of few reports of vascular tumors were restricted to the nasal cavity and uterus.
The present study therefore, is aimed at determining the relative frequency and histopathological patterns of these neoplasms as seen in University of Benin Teaching Hospital (UBTH), Benin-City, Nigeria. We hope to bring to the awareness of clinicians how common these entities are and what types to expect in our environment especially where many Hospitals lack histopathology facilities.
| Materials and Methods|| |
Study setting and design
The study is a 12 year retrospective analysis of all histologically confirmed benign and malignant vascular neoplasms in the Department of Pathology, UBTH, Benin-City between January 1994 and December 2005. The pathology request cards were retrieved in order to obtain data on age, sex, clinical features, type of biopsy and diagnosis. In addition, description of the gross morphology and location of individual neoplasms was also recorded.
Specimen sampling and laboratory procedures
The routine hematoxylin and eosin (H and E) stained slides of specimens were retrieved from the records of the pathology department and histologically examined. Where the glass slides are missing or broken, fresh sections were prepared and stained from stored original tissue blocks. Special histochemical stains such as Masson's trichrome were applied to delineate the basic architectural frame work of the lesions. Periodic acid Schiff and reticulin stains were used to outline vascular basement membrane, endothelial cells and to differentiate endothelial tumors from peri-vascular tumors and to aid the diagnosis of these vascular tumors where necessary. The tumors were classified into benign, intermediate and malignant categories according to World Health Organization's guidelines. 
All cases of missing H and E stained slides and paraffin-embedded tissue blocks and all previously diagnosed cases in which a vascular origin could not be substantiated on microscopic review were excluded from this study. All cases of incomplete bio-data of the patients were also excluded from the study.
The data were analyzed using the statistical Package for the Social Sciences version 16 Incorporated, Chicago, Illinois, USA.
| Results|| |
During the 12 year period, a total of 14,438 surgical specimens were received in the department of pathology, UBTH Benin-City, out of which 870 were soft-tissue tumors. 162 vascular tumors met the criteria for inclusion in this study while 18 were excluded for reasons of incomplete clinical data or unavailable blocks and slides. These 162 vascular tumors represent 1.1% of all lesions and 18.6% of all soft-tissue tumors diagnosed during the period. The breakdown shows that there were 136 (83.9%) benign tumors, 24 (14.8%) malignant tumors and 2 (1.3%) borderline tumors.
[Table 1] shows the overall prevalence and sex distribution of all the histological subtypes of vascular tumors seen in this study. The most common group of tumors is the hemangiomas which accounted for 115 (71%) cases of all vascular tumors and 84.6% of the benign tumors. Lymphangiomas constituted (n = 15) 9.3% of all vascular tumors and 11% of the benign group. Among the perivascular tumors, hemangiopericytoma and glomus tumor constituted 3.1% and 0.6% of all vascular tumors respectively while hemangioendothelioma constituted 1.2% of all tumors. The overwhelming majority of malignant vascular tumors were KS constituting 91.7% of the malignant category and overall 13.6% of all vascular neoplasms. Angiosarcomas made up the rest of the malignant neoplasms and constituted 1.2% of all tumors in this study. The overall male:female ratio (M:F) is 1:1.2 with a slight tilt toward the female population. This again is maintained in both benign and malignant categories constituting an M:F ratio of 1:1.1 and 1:1.2 respectively.
[Table 2] and [Table 3] show the age distribution of vascular tumors. The overall age range was 22 days-95 years. The peak age bracket of occurrence of benign and malignant vascular tumors was 0-10 years and 31-40 years respectively. For the individual lesions, the hemangiomas and lymphangiomas show similar peak incidence in the 1 st and 2 nd decades. In contrast, KS had a peak incidence in the 3 rd and 4 th decades.
|Table 3: The age distribution of the various histological types of tumors|
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[Table 4] shows that the predominant sites of occurrence of vascular tumors in this study were head and neck (39.5%), upper limbs (16.7%) and lower limbs (14.2%), which collectively accounted for 73.5% of all cases. The trunk was a relatively less frequent site of occurrence with only 8% of tumors being sited there.
| Discussion|| |
A total of 162 histologically confirmed vascular tumors received at the UBTH, Benin-City over a 12-year period were reviewed in this study. This gives an average of approximately 11 cases/year. This figure though low is in keeping with those reported from other centers in Nigeria. Malami and Banjo  had an average 19 cases/year in Lagos western Nigeria while Rafindadi  had an average of 13 cases/year in Zaria northern Nigeria. However, these data are not in tandem with those from outside Nigeria where the relative frequency of vascular tumors are higher. , Under-reporting and the absence of cancer registry in this center contributes to this low frequency. Again high patronage for alternative medication as well as indolent nature of majority of these vascular tumors and poverty contribute to this apparently lower frequency of vascular tumors in this environment.
Benign vascular tumors constituted the overwhelming proportion of vascular tumors in this study. Benign vascular tumors constituted 83.9% while 14.8% were malignant and 1.2% was of intermediate or borderline malignancy. These figures are similar to those obtained from Zaria and Lagos in Nigeria and the United States of America. ,, The mean age at diagnosis of vascular tumors in this study is 27.9 years with a peak age bracket of 0-10 years. 98 (60.5%) of these vascular lesions occurred in the first 3 decades and this predilection for the young is even more prominent for the benign tumors in which 65% occurred in the first 3 decades. This is not an unexpected finding as many vascular tumors are congenital (principally hemangiomas and lymphangiomas) and present first in childhood. , All the three cases of benign vascular tumors occurring after the 7 th decade in this study are pyogenic granulomas, which may develop at any age. 
The M:F ratio in this study was 1:1.2 showing a slight female bias study. Noteworthy however pyogenic granuloma shows a strong female predilection (M:F = 1:1.7) accounted almost entirely for tilting the overall M:F ratio in favor of females. This is in similar to the documented higher incidence in women of the childbearing age, pregnancy and the use of oral contraceptives. , This finding however is comparable to reports from the USA nevertheless it is at variance with earlier reports from Lagos and Zaria in Nigeria. , The M:F ratio of hemangiomas of 1:1.1 in this study is in conformity with most other reports which show a slight female predilection. ,,
The various histological subtypes of hemangioma (capillary and cavernous hemangioma and pyogenic granuloma) constituted 71% of all vascular tumors and 84.6% of the benign tumors in this study. These constitutes the most common tumor in infancy and childhood. ,,,, The well-documented predilection of hemangiomas accounting for 43.5% in the head and neck region is also seen in this study. Lymphangiomas constituted 11% of the benign vascular tumors and thus are the second most common benign vascular tumors in this study. This relative rarity is in consonance with the findings of Andersen  in New York, where only 6.3% of lymphangiomas occurred as benign tumors and Rafindadi  in Zaria, Nigeria which documented 17.2% of lymphangiomas. 73% of the lymphangiomas in this review presented within the first 2 decades of life. This is in line with the concept that they are developmental abnormalities arising from sequestered lymphatic channels that have failed to link up with the rest of the lymphatic system or with the venous system during embryological development. ,, 53% of the lymphangiomas were located in the head and neck region of the body. This is in line with the well-documented fact that though they can affect almost any part of the body they show a predilection for the head, neck and axilla which together accounts for more than half of all lymphangiomas. 
The perivascular tumors found in this study were glomus tumor and hemangiopericytoma. This is in keeping with the well-documented rarity of these tumors in literatures. Similarly only one case of glomus tumor was diagnosed during the 12 years study. In a review of five hundred consecutive soft-tissue tumors at the Mayo clinic, only 1.6% was glomus tumors. , Hemangiopericytoma accounted for 3% of all vascular tumors in this review. It is primarily a tumor of adult life; a fact that is well borne out in this study where four of the five hemangiopericytoma occurs in subjects that are 40 years and above. 
Hemangioendothelioma is vascular tumors of intermediate malignancy with ambiguous histological features. , They are uncommon in this series constituting 1.2% of all vascular tumors. The two cases in this study were both in females, thus correlating with other series, which shows a propensity for female bias. ,,
KS constituted the overwhelming majority of malignant vascular tumors in this study for 91% of the cases and 13.6% of all vascular tumors. It was the appearance of aggressive forms of KS in the United States that heralded the onset of AIDS epidemic in western countries. In the absence of AIDS, KS occurs rarely in three distinct epidemiologic forms: The classic form, the endemic form and transplant related forms.  Before the human immunodeficiency virus (HIV) epidemic, KS showed a greater geographic variation in incidence than almost any other cancer. It was as common in parts of sub-Saharan Africa, such as Uganda and eastern Zaire as colon cancer is in Europe and the United States. In all these areas, KS was considerably more common in men than in women.  However, parts of Africa with a high prevalence of HIV and where KS was relatively common even before the era of AIDS have seen an explosion in the incidence of the disease. In the past decade, the incidence of KS has increased about 20-fold in Uganda and Zimbabwe, such that it is now the most common cancer in men and the second most common in women. , Similarly, between 1988 and 1996, the incidence of KS has risen at least threefold in South Africa and continues to increase as the HIV epidemic grows.  The M:F ratio of 1:1.2 of KS in this study correlates with more recent epidemiological data showing a trend toward a reversal of the previously overwhelming preference for the male gender by this tumor in the pre-AIDS era. For example, data from the South African National Cancer Registry show that between 1992 and 1996, the incidence rates of KS have doubled in men, but have increased about seven-fold in women, such that the sex ratio of 7:1 in males versus females in 1988 has now declined drastically to 2 males to 1 female. 
There are two cases of KS in the pediatric age group in this study - one case in a 6-month-old infant and the other in a 4-year-old child with both cases reported in lymph nodes. This is not a new finding as endemic (lymphadenopathic) KS has been known to affect infants and children and run a more rapid and aggressive course. 
Angiosarcomas are malignant endothelial neoplasms that occur most commonly in the skin, soft-tissue, breast and liver with an equal male to female distribution. They are collectively one of the rarest forms of soft-tissue neoplasms accounting for only 1% of all sarcomas as estimated by a 20-year study at the MD Anderson Hospital  and they constitute 1.2% of all vascular neoplasms in the present study. The two cases of angiosarcoma in this review are both located in the skin of the scalp, which is in keeping with their known preference for skin and superficial soft-tissue in sharp contrast to the deep location of most soft-tissue sarcomas.  Chronic lymph-edema is a well-recognized predisposing factor in angiosarcomas of the skin and soft-tissue. This occurs typically in women with post-mastectomy radiotherapy for breast cancer. Furthermore, chronic lymph-edema occurring on a congenital, idiopathic, traumatic or infectious basis also predisposes to angiosarcoma. , None of these etiological associations could be established in this study due to a paucity of adequate clinical information.
| Conclusion|| |
This study has shown that vascular tumors constitute a significant proportion of soft-tissue tumors seen in our environment and that the vast majority of these tumors are benign. The various diagnostic subtypes of hemangiomas collectively accounts for an overwhelming proportion of these tumors and that KS constituted the majority of the malignant vascular tumors. Although vascular tumors occur in any part of the body, they are however most common in the head and neck region.
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[Table 1], [Table 2], [Table 3], [Table 4]