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Only patients with measurable disease at baseline should be included in protocols where objective tumor response is the primary endpoint. Measurable disease – the presence of at least one measurable lesion. If the measurable disease is restricted to a solitary lesion, its neoplastic nature should be confirmed by cytology/histology.
The 5th WHO classification delineates distinct types of tumors, some of them being further divided into subtypes, rendering the former terms entity and variant obsolete. When molecular diagnostics are not complete enough to allow precise classification, diagnosis should be designated by appending not otherwise specified (NOS).
The critical step in treatment planning is to determine the correct histology of the tumor. Misidentification of the tumor histology can lead to errors in treatment and prognosis. [24] Atypical teratoid/rhaboid tumor closely resembles medulloblastoma, [25] primitive neuroectodermal tumor, choroid plexus carcinoma, and some kinds of germ cell tumor.
Grading in cancer is distinguished from staging, which is a measure of the extent to which the cancer has spread. Pathology grading systems classify the microscopic cell appearance abnormality and deviations in their rate of growth with the goal of predicting developments at tissue level (see also the 4 major histological changes in dysplasia ).
Cytopathology is commonly used to investigate diseases involving a wide range of body sites, often to aid in the diagnosis of cancer but also in the diagnosis of some infectious diseases and other inflammatory conditions. [3]
Pilocytic astrocytoma (and its variant pilomyxoid astrocytoma) is a brain tumor that occurs most commonly in children and young adults (in the first 20 years of life). They usually arise in the cerebellum, near the brainstem, in the hypothalamic region, or the optic chiasm, but they may occur in any area where astrocytes are present, including the cerebral hemispheres and the spinal cord.
Brain biopsy. HPS stain. The current standard for diagnosis typically includes positive CSF cytology, vitreous biopsy, or brain/leptomeningeal biopsy. [10] Histopathological confirmation is essential for definitive diagnosis. [11] MRI or contrast enhanced CT classically shows multiple ring-enhancing lesions in the deep white matter.
Micrograph of psammoma body in the centre of the field in a meningioma of brain. H&E stain. A psammoma body is a round collection of calcium, seen microscopically. The term is derived from Greek άμμος (ámmos) ' sand '.