Sero – prevalence of hepatitis b surface antigen among individuals with hiv – related cutaneous disorders at a tertiary referral dermatology clinic in dar es salaam
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MORPHOLOGICAL PATTERN AND FREQUENCY OF INTRACRANIAL MENINGIOMA IN TANZANIA HA Mwakyoma1 and JF Kahamba2 Summary Objective: The objective of the study was to study the histological pattern of intracranial meningiomas, provide a comprehensive data about its frequency in both adults and children and to correlate the site of the tumour with histological diagnosis. Design: A descriptive study. Place and duration of study: The study was carried out at the departments of Histopathology and Morbid Anatomy, Muhimbili National Hospital and Neurosurgery, Muhimbili Orthopaedic Institute in Tanzania, over a period of seven years (1998 to October 2004). Patients and methods: The histopathological data of 54 intracranial meningiomas of adults and children was evaluated on H & E stained sections of paraffin embedded tissue. Results: The ages ranged from 6 to 87 years with mean of 36.6 years. The male to female ratio was 1:1. All histological subtypes of meningiomas were in WHO grade I category and meningotheliomatous type comprised the largest subtype (37%). Others were transitional (25.9%), fibroblastic (22.2%), angiomatous (7.4%), psamommatous (5.6%) and microcystic (1.9%). Out of 54 meningiomas, 43 (79.6%) were supratentorial and 11 (20.4%) were infratentorial in location. Meningotheliomatous meningioma was the commonest histological subtype in supratentorial region (41.9%) while in infratentorial region fibroblastic and transitional subtypes were the commonest (36.4% each). Conclusion: All meningioma were in WHO grade I category and meningotheliomatous was the commonest overall and also the most predominant in the supratentorial region while in infratentorial location transitional and fibroblastic subtypes were the commonest with equal frequency. Meningioma gave an equal gender ratio in our study. Keywords: Brain tumours, meningioma, location, Gender. Correspondence to: Mwakyoma HK, Box 65002, Muhimbili University College of Health Sciences, Dar es Salaam, Tanzania. 1Dept. of Histopathology and Morbid Anatomy, MUCHS, 2Dept. of Neurosurgery, Muhimbili Orthopaedic Institute. Introduction Meningiomas arise from arachnoid cells in the meninges. Overall they are the most common type of benign brain tumour. They occur twice as often in women as in men(1). Meningiomas (WHO grades I - I I I) are typically slow-growing, benign, tumours attached to the dura matter and composed of neoplastic meningothelial (arachnoid) cells.(3,15) Meningiomas are estimated to comprise between 13% and 26% of primary brain tumours.(3) Meningiomas usually occur in adults, with a peak occurrence during the sixth and seventh decades of life. Women are affected more than men, with a female: male ratio as high as 2:11,3 and occur between 30 and 50 years of age. Atypical meningiomas (WHO grade II) constitute 4.7% to 7.2% of meningiomas, while anaplastic (malignant) meningiomas (WHO grade III) account for 1.0% to 2.8% of meningiomas(3), these higher grade meningiomas may show a conspicuous predominance in males. Most meningiomas are extra-axial dural based lesions. Ninety percent are supratentorial. They typically grow along intradural venous sinuses, at the confluence of dura septa (falcotentorial junction) or at the confluence of cranial sutures (pterion). Ten percent are infratentorial and arise from petrous bone in the cerebropontine angle, the clivus, the tentorium and the tentorial incisura.(3) Meningiomas have a wide range of histologic appearances15. These include: (1) Meningiothelial, fibrous (fibroblastic) transitional (mixed), psammomatous, angiomatous, microcysti2, secretory, lymphoplasmacyte-rich, metaplastic (WHO grade I). (2) Atypical, chordoid, clear cell (WHO grade I I) and (3). Anaplastic (malignant), rhabdoid, papillary. (WHO grade lll). Malignant behaviour, including brain invasion may occur in grades II and III of meningioma. Some of these tumours are known to be induced by ionizing radiation, with an average of time interval to tumour appearance of 19 to 35 years, depending on the dose of radiation.(3,4) Most patients with radiation induced meningiomas have a history of low-dose radiation to the scalp for tinea capitis; the second largest number of radiation-induced meningiomas often occurs inpatients who have received high-dose radiation for primary brain tumours.(4,9,10) In general, radiation-induced meningiomas occur more frequently over the convexities; in about 80% of cases, they have a more frequent recurrence and exhibit malignant behaviour, as indicated histologically by hypercellularity and pleomorphism.(9,10) Hormonal factors (e.g. estrogen, progesterone) have been studied extensively as risk factors for meningiomas because of the striking predominance of meningiomas in women.(6,7,8) The progesterone receptor is the best candidate as an aetiology for meningiomas.(6,7) Progesterone receptors have been shown to be expressed in 81% of women and in 40% of men with meningiomas.(7) Other evidence to substantiate the implication of gender –specific hormones comes from data showing increased growth of meningiomas during pregnancy and size changes with menses.(11) Race variability has been shown in the prevalence of maningiomas among Caucasians, Africans, African Americans, and Asian.(12) A greater incidence exists among Africans than Caucasians. Among Caucasians, 75% of meningiomas occur in women, and 25% occur in men. African show equal gender ratio. Multiple meningiomas often occur in patients with neurofibromatosis 2 (NF2) and in other, non-NF2 families with a hereditary predisposition to meningioma.(13) Approximately 75% of all meningiomas display some cytogenetic abnormalities.(5) The most cytogenetic alteration in meningioma involves a deletion of chromosome 22. Genetic and cytogenetic alterations accumulate with progression from WHO grade I to WHO grade III lesions.(2,5) Mutations in the NF2 gene have been detected in up to 60% of sporadic meningioma. The major evolution of meningioma is reccurence. The tumour grade provides the most useful predictor of recurrence.(14) Benign meningiomas have a recurrence rate of about 7-20% while atypical meningiomas recur in 29-38% of cases, and anaplastic neningiomas in 50-78% of cases. So, proliferation indices have been used to predict recurrence and survival.(14) Broad Objective To study the histological pattern of intracranial meningiomas and provide a comprehensive data about its frequency inpatients and to correlate the site of lesion with the histological diagnosis. Specific Objectives To determine the histological pattern of intracranial meningioma. To determine the age and sex distribution of intracranial meningioma To provide a comprehensive data about the frequency of meningioma in patients. To correlate the site of meningiomas with the histological diagnosis. Patients and methods A study covering period of seven years (January 1998 to October 2004) was conducted in the department of Histopathology and Morbid Anatomy, Muhimbili National Hospital (MNH) and department of Neurosurgery, Muhimbili Orthopaedic Institute (MOI) in Dar es Salaam. Records of all biopsies of intracranial meningiomas performed at the above mentioned hospitals along with the clinical history of patients were reviewed. Biopsies received in 10% buffered formalin were processed and embedded in paraffin. Histological sections 5 µm thick were prepared and stained by haematoxylin and Eosin (H&E). The histological characterization of meningiomas was done according to the WHO histological typing of tumours of CNS15. Results: The age of patients with intracranial meningioma ranged from 6 to 87 years with a mean age of 36.6 years. There were 27 males and 27 females with a male to female (M:F) ratio of 1:1 (Table 1). A total of 54 intracranial meningiomas were diagnosed during the study period. All histological subtypes of meningiomas were in WHO grade I and comprised of menigotheliamatous (37%) transitional (25.9%), fibroblastic (22.2%), angiomatous (7.4%), psamommatous (5.6%) and microcytic meningioma (1.9%) (table 2). Out of 54 cases of intracranial meningiomas, 43 (79.6%) were supratentorial and 11(20.4%) were infratentorial in location. Meningotheliomatous subtype was the commonest category among the meningiomas in the supratentorial region and comprised of 41.9% of all meningiomas at this location. However, Fibroblastic and Transitional Subtypes were the commonest types of meningioma in infratentorial region and comprised of (36.4% each) at this site (table 2). As regards to location and grading of meningiomas, it was found that their grading (WHO grading) was that of grade I in all cases in the two locations and thus statistically there was no difference. Discussion: Meningiomas are estimated to comprise between 13% and 26% of primary brain tumours. Information retrieved from cancer registry and files at Muhimbili National Hospital showed that meningiomas comprised of 52% of primary brain tumours in our study. Other studies(6,12) show a lower incidence of meningioma than ours among the primary brain tumours. It was not known for reasons of higher incidence of meningioma among the primary brain tumours in our study. Further studies are needed to elucidate the reasons for this increased incidence. Meningiomas usually occur in adults between 30 and 50 years of age with peak during the sixth and seventh decade.(1,3) In our study the mean age of occurrence was 36.6 years with a peak age of occurrence between 30 – 60 years. Our series show a relatively lower age of occurrence of meningioma compared to other studies in Western countries.(1,3,6,12) Some environmental, hormonal or genetic factors may be responsible for the lower age of occurrence of meningioma in Tanzania. This needs further studies. In some studies variability have been shown in the prevalence of meningiomas among different races as well as in gender.(6) Among Caucasians, 75% of meningiomas occur in women, and 25% in men while Africans show equal gender ratio6,12. This is in agreement with findings in our study whereby the study subjects were predominantly Africans and the male to female (M:F) ratio was 1:1. Other studies in Western Countries show a marked high frequency in females. The strong female predilection of meningiomas over males has been linked to sex hormone influence in many studies 5,7. Reasons as to why in Africans there is an equal gender ratio could not be elucidated in this study and we can only extrapolate that some genetic predisposition and environmental factors may be responsible and this needs further studies to confirm. In our series, the histological classification of meningioma (WHO 2000)(15) fell in the WHO grade I category (Typical meningioma). Meningiomas in this category are benign and slow growing. In other studies WHO grade I comprised of 90% of mangiomas. However, WHO grade II, III and IV were not encountered in our study. Among the histological types in WHO grade I meningiomas, meningotheliomatous type was the commonest and accounted for 37% of all meningiomas. This is in agreement with some studies.(15) In our study, supratentorial region was the most frequent site of meningiomas and meningotheliomatous type constituted the commonest histological type and accounted for 41.9% of all histological types of meningiomas. Eleven (20.4%) meningiomas occurred in infrantentorial region and transional and fibroblastic meningiomas were the most frequent histological types and accounted for 72.7% (36.3% each) at this site. Studies have shown that the major evolution of meningioma is recurrence, and tumour grade provides the most useful predictor of recurrence14. So, proliferation indices have been used to predict recurrence and survival14. Due to the fact that in our series all meningiomas were in WHO grade I category, it is expected that the recurrence rate would be lower with a better survival than if the grades were higher.
It is hoped that this study will provide baseline data concerning meningiomas in Tanzania. It is concluded that meningiomas were more frequent in the supratentorial region and meningotheliomatous was the commonest histological type. However, fibroblastic and transitional were the most common histological types in the infratentorial location. Meningiomas gave an equal gender ratio in our study. Table 1: Histological types of meningioma by age and sex distribution (n=54)
MT: Meningotheliomatous M= 27 FIB: Fibroblastic F= 27 T: Transitional PS: Psamommatous A: Angiomatous MIC: Microcystic M: Male F: Female Table 2. Histological types and site distribution of meningioma (n=54)
References
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