Background
Astrocytomas are CNS neoplasms in which the predominant cell type is derived from an immortalized astrocyte. Two classes of astrocytic tumors are recognized—those with narrow zones of infiltration (eg, pilocytic astrocytoma, subependymal giant cell astrocytoma, pleomorphic xanthoastrocytoma) and those with diffuse zones of infiltration (eg, low-grade astrocytoma, anaplastic astrocytoma, glioblastoma). Members of the latter group share various features, including the ability to arise at any site in the CNS, with a preference for the cerebral hemispheres; clinical presentation usually in adults; heterogeneous histopathological properties and biological behavior; diffuse infiltration of contiguous and distant CNS structures, regardless of histological stage; and an intrinsic tendency to progress to more advanced grades.
Numerous grading schemes based on histopathologic characteristics have been devised, including the Bailey and Cushing grading system, Kernohan grades I-IV, World Health Organization (WHO) grades I-IV, and St. Anne/Mayo grades 1-4. Regions of a tumor demonstrating the greatest degree of anaplasia are used to determine the histologic grade of the tumor. This practice is based on the assumption that the areas of greatest anaplasia determine disease progression.
This chapter focuses on the widely accepted WHO grading scheme that relies on assessments of nuclear atypia, mitotic activity, cellularity, vascular proliferation, and necrosis. WHO grade I corresponds to pilocytic astrocytoma, WHO grade II corresponds to low-grade (diffuse) astrocytoma, WHO grade III corresponds to anaplastic astrocytoma, and WHO grade IV corresponds to glioblastoma multiforme (GBM). This article is confined to low-grade and anaplastic astrocytomas. GBM and pilocytic astrocytoma are not discussed in this chapter (for more information, see Glioblastoma Multiforme).
Pathophysiology
Regional effects of astrocytomas include compression, invasion, and destruction of brain parenchyma. Arterial and venous hypoxia, competition for nutrients, release of metabolic end products (eg, free radicals, altered electrolytes, neurotransmitters), and release and recruitment of cellular mediators (eg, cytokines) disrupt normal parenchymal function. Elevated intracranial pressure (ICP) attributable to direct mass effect, increased blood volume, or increased cerebrospinal fluid (CSF) volume may mediate secondary clinical sequelae. Neurological signs and symptoms attributable to astrocytomas result from perturbation of CNS function. Focal neurological deficits (eg, weakness, paralysis, sensory deficits, cranial nerve palsies) and seizures of various characteristics may permit localization of lesions.
Infiltrating low-grade astrocytomas grow slowly compared to their malignant counterparts. Doubling time for low-grade astrocytomas is estimated at 4 times that of anaplastic astrocytomas. Several years often intervene between the initial symptoms and the establishment of a diagnosis of low-grade astrocytoma. One recent series estimated the interval to be approximately 3.5 years. The clinical course is marked by a gradual deterioration in one half of cases, a stepwise decline in one third of cases, and a sudden deterioration in 15% of cases. Seizures, often generalized, are the initial presenting symptom in about one half of patients with low-grade astrocytoma.
For patients with anaplastic astrocytomas, the growth rate and interval between onset of symptoms and diagnosis is intermediate between low-grade astrocytomas and glioblastomas. Although highly variable, a mean interval of approximately 1.5-2 years between onset of symptoms and diagnosis frequently is reported. Compared to low-grade lesions, seizures are less common among patients with anaplastic astrocytomas. Initial presenting symptoms most commonly are headache, depressed mental status, and focal neurological deficits.
Mortality/Morbidity
Morbidity and mortality, as defined by the length of a patient's history and the odds of recurrence-free survival, are correlated most highly with the intrinsic properties of the astrocytoma in question. Typical ranges of survival are approximately 10 years from the time of diagnosis for pilocytic astrocytomas (WHO grade I), more than 5 years for patients with low-grade diffuse astrocytomas (WHO grade II), 2-5 years for those with anaplastic astrocytomas (WHO grade III), and less than 1 year for patients with glioblastoma (WHO grade IV).
Race
Although genetic determinants are recognized in astrocytoma development and progression, astrocytomas do not differ intrinsically in incidence or behavior among racial groups. Demographic and sociological factors, such as population, age, ethnic attitude toward disease, and access to care, have been reported to influence measured distributions.
Sex
No clear sex predominance has been identified in the development of pilocytic astrocytomas. A slight male predominance, with a male-to-female ratio of 1.18:1 for development of low-grade astrocytomas, has been reported. A more significant male predominance, with a male-to-female ratio of 1.87:1 for the development of anaplastic astrocytomas, has been identified.
Age
Most cases of pilocytic astrocytoma present in the first 2 decades of life. In contrast, the peak incidence of low-grade astrocytomas, representing 25% of all cases in adults, occurs in people aged 30-40 years. Ten percent of low-grade astrocytomas occur in people younger than 20 years; 60% of low-grade astrocytomas occur in people aged 20-45 years; and 30% of low-grade astrocytomas occur in people older than 45 years. The mean age of patients undergoing a biopsy of anaplastic astrocytoma is 41 years.
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Showing posts with label cancer. Show all posts
Showing posts with label cancer. Show all posts
Sunday, 5 October 2008
Tuesday, 1 July 2008
Adrenal Carcinoma
Adrenocortical cancers (ACs) are uncommon malignancies that can have protean clinical manifestations. Adrenocortical masses are common; autopsy studies show that approximately 5-15% of the general adult population may have adrenal incidentalomas. Adrenal incidentalomas are biochemically and clinically asymptomatic adrenal masses found incidentally as a result of unrelated imaging investigations such as abdominal CT or MRI scans. Findings from abdominal CT scans suggest that the prevalence rate is 1-5%. Only a small number of adrenal tumors are functional and an even smaller number (approximately 1%) are malignant.
Regardless of size, approximately 1 per 1500 adrenal tumors is malignant. The evaluation of these incidentalomas, therefore, focuses on (1) identifying functional masses and treating them appropriately (including surgical removal); (2) identifying adrenal carcinomas early, with the intent of attempting complete surgical extirpation; and (3) reassuring the patients who do not fit either of these classes and arranging for their subsequent follow-up.
Although the means of identifying ACs from this subpopulation still are controversial, virtually all authorities agree about removing all nonfunctional adrenal tumors larger than or equal to 6 cm because of the significant potential cancer risk. Authorities also generally agree that nonfunctional adrenal tumors (£3 cm) have a very low probability of being adrenal cancer; therefore, they can be removed safely.
The management strategy for adrenal masses larger than 3 cm and less than 6 cm is disputed. Some authorities suggest lowering the threshold for surgical removal of nonfunctional masses from 6 cm to 4-5 cm. Others individualize the follow-up of these patients depending on their clinical status, CT scan characteristics, and age. Particularly important is the fact that these criteria do not apply to children, who generally have smaller ACs. A review of the available data suggests that the incidence rate of malignancy is small Frequency
International
AC tumors are uncommon. The incidence is approximately 0.6-1.67 cases per million persons per year. Some reports suggest an inordinately high frequency (up to 10-fold higher) of cases among children in southern Brazil, for unknown reasons. Overall, AC accounts for 0.02-0.2% of all cancer-related deaths; therefore, it is relatively rare.
Race
AC has no specific racial predilection.
Sex
The female-to-male ratio is approximately 2.5-3:1. Male patients tend to be older and have a worse overall prognosis than female patients. Female patients are more likely than male patients to have an associated endocrine syndrome. Nonfunctional ACs are distributed equally between the sexes.
Age
AC occurs in 2 major peaks: in the first decade of life and again in the fourth to fifth decades. Approximately 75% of the children with AC are younger than 5 years. Functional tumors also are more common in children, while nonfunctional tumors are more common in adults.
Read more HERE
Regardless of size, approximately 1 per 1500 adrenal tumors is malignant. The evaluation of these incidentalomas, therefore, focuses on (1) identifying functional masses and treating them appropriately (including surgical removal); (2) identifying adrenal carcinomas early, with the intent of attempting complete surgical extirpation; and (3) reassuring the patients who do not fit either of these classes and arranging for their subsequent follow-up.
Although the means of identifying ACs from this subpopulation still are controversial, virtually all authorities agree about removing all nonfunctional adrenal tumors larger than or equal to 6 cm because of the significant potential cancer risk. Authorities also generally agree that nonfunctional adrenal tumors (£3 cm) have a very low probability of being adrenal cancer; therefore, they can be removed safely.
The management strategy for adrenal masses larger than 3 cm and less than 6 cm is disputed. Some authorities suggest lowering the threshold for surgical removal of nonfunctional masses from 6 cm to 4-5 cm. Others individualize the follow-up of these patients depending on their clinical status, CT scan characteristics, and age. Particularly important is the fact that these criteria do not apply to children, who generally have smaller ACs. A review of the available data suggests that the incidence rate of malignancy is small Frequency
International
AC tumors are uncommon. The incidence is approximately 0.6-1.67 cases per million persons per year. Some reports suggest an inordinately high frequency (up to 10-fold higher) of cases among children in southern Brazil, for unknown reasons. Overall, AC accounts for 0.02-0.2% of all cancer-related deaths; therefore, it is relatively rare.
Race
AC has no specific racial predilection.
Sex
The female-to-male ratio is approximately 2.5-3:1. Male patients tend to be older and have a worse overall prognosis than female patients. Female patients are more likely than male patients to have an associated endocrine syndrome. Nonfunctional ACs are distributed equally between the sexes.
Age
AC occurs in 2 major peaks: in the first decade of life and again in the fourth to fifth decades. Approximately 75% of the children with AC are younger than 5 years. Functional tumors also are more common in children, while nonfunctional tumors are more common in adults.
Read more HERE
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