Brain tumors of childhood: nosological and diagnostic problems

Incidence of childhood brain tumors in Syria (1993-2002)

OBJECTIVE

To determine whether the incidence and location of childhood CNS tumors in Syria follows the same pattern described in Western and Far Eastern countries.

PATIENTS AND METHODS

We analyzed the data compiled from 367 children with brain tumors operated on in our Department of Neurosurgery between 1993 and mid-2002. We excluded all vascular and metastatic lesions and adopted the latest WHO classification in grouping all glial tumors.

RESULTS

We found that 47% of brain tumors were located in the supratentorial, and 53% in the infratentorial region. The ratio of male to female occurrence was 1:1.2 (52% males, 48% females). For lesions in the supratentorial space, the distribution was 56% males and 44% females, while in the posterior fossa, the distribution was 61% males and 39% females. Low-grade tumors (WHO I/II) constituted 53.5% of all lesions, and the rest were high grade tumors (WHO III/IV) 46.5%. The most common tumor found in our childhood population was medulloblastoma (27.5%), followed by astrocytoma (25.8%), then craniopharyngioma (14.1%). The most common tumor in the posterior fossa was medulloblastoma (53.5%), followed by astrocytoma (22.5%), then ependymoma (17%). The most common tumors in the supratentorial space were astrocytoma and craniopharyngioma.

CONCLUSIONS

In our patient population, the incidence and distribution of CNS tumors were somehow different than those reported by authors from the Western and Far Eastern countries. Whether these results are unique to Syria, or reflect a regional difference in the disease distribution between the Middle East region and the rest of the world, remains to be determined.

Brain tumors in childhood and adolescence

Brain tumors are the second most common neoplasm in childhood and adolescence. With the recent advances in technology, changes in tumor incidence have been reported. This study examines this statement. A 19-year retrospective case review of primary brain tumors in persons younger than 18 years of age at time of diagnosis, who had permanent residence in our catchment area, was performed. Data were examined for changes in presenting symptoms and signs and incidence rates for tumors on the basis of anatomic location and histologic tumor type. An incidence rate of 2.76 per 100,000 people younger than 18 years of age was found. During the period of this study a small, but significant, trend toward increasing incidence was evident. No changes in patterns of presentation or duration of symptoms before diagnosis was observed. The incidence rate based on histologic tumor diagnosis remained fairly constant during the study period.

Tumor cell proliferation and apoptosis in medulloblastoma

The distribution of proliferating cell nuclear antigen (PCNA)-(clone PC 10)- and Ki-67-(clone MIB-1)-positive nuclei was investigated in 60 medulloblastomas of childhood. Although the labeling index of the two markers did not coincide, both showed a wide range of parallel variations. The percentage of positive nuclei was similar in both classic and desmoplastic tumors. A variable proliferation capacity was found in the different tumor structures. Areas with neuronal and glial differentiation showed very few positive nuclei; these were very abundant in the infiltration areas, and along penetrating vessels from subarachnoidal growths. Pale islands were negative or positive only in their peripheral part. Large-cell areas were richer in positive nuclei than classic ones, accounting for their more malignant character. Hyperchromatic round nuclei, not belonging to necrotic foci and called lymphocyte-like nuclei, differently interpreted in the past, were variably found in every case. They are known, from previous experience, to stain orange with Acridine Orange fluorochroming, like single-stranded DNA. They were not easily distinguishable from mitoses and were stained by in situ end-labeling of DNA strand breaks, as demonstrated by incorporation of labeled nucleotides. They were regarded as possible apoptotic nuclei, representing either a peculiar type of cell death or the preservation of the cell deletion capacity, typical of the embryonal tissue of origin.

Central nervous system tumors in Mexican children

Five hundred and seventy primary central nervous system (CNS) tumors from the Department of Pathology at the National Institute of Pediatrics in Mexico City, collected from 1970 to 1989, were histologically reclassified in order to find out their relative incidence as well as their outstanding features. With this, we could establish a frame of reference for our local population, contributing to the epidemiological analysis of these entities. All the tumors were examined independently by two pathologists (C.R. and M.R.), using the classification of Rorke et al. Histological type, patient age and sex, and tumor location were analyzed. CNS tumors were the secondmost frequently encountered solid tumors, after lymphomas, and were increasing in incidence at a rate of 2.2 annually. Children in the age group 0-9 years were most often affected, and there was a predominance of male patients. Astrocytoma and medulloblastoma were the most common tumor types. The infratentorial region was the most frequent tumor location in the 2- to 9-year age group. By contrast, in the under 2-year-olds a supratentorial location was more frequent, and the incidence of germ cell tumors was proportionally high. In general, some histological types seemed to be associated with particular age groups. Although we found primitive neuroectodermal tumors to be the fifth most common at all ages (except for medulloblastoma), many other authors do not report a similar finding.

Age-related immunoreactivity pattern in medulloblastoma

Thirty-five paraffin-embedded medulloblastomas (19 from children and 16 from adults; 24 classic medulloblastomas, 10 desmoplastic medulloblastomas, 1 tumor with neuronal differentiation) were examined for reactions with antibodies against glial fibrillary acidic protein (GFAP), cytokeratins KL1 and MNF116, desmin, and vimentin. Only the tumor from the youngest patient, a 152-day-old boy, showed a positive immunoreaction for cytokeratins. Because of this age-related expression of cytokeratins in medulloblastomas primarily in very young children, cytokeratin positivity was interpreted as a sign of tumor immaturity. Five medulloblastomas showed scattered GFAP-positive reactive astrocytes and/or other positive, probably neoplastic, cells. Only two tumors showed GFAP immunoreactivity in unequivocally neoplastic cells. Of six tumors that reacted with vimentin, three showed strong reactivity throughout, one being the tumor from the 152-day-old boy. The remaining three demonstrated nests of vimentin-positive cells with weak or intense somatic immunoreactivity for vimentin. None of the 35 cases showed positivity for desmin; indicating that mesenchymal differentiation is restricted to the rare so-called medullomyoblastomas.