General Approach and Differential Diagnosis



General Approach and Differential Diagnosis





Clinical and Neuroimaging Variables

The interpretation of routine H&E-stained sections and immunohistochemistry from CNS lesions can be difficult and risky when performed outside of the context of clinical and neuroimaging data. Indeed, many difficulties may arise from attempts to establish a diagnosis based on morphology alone. As detailed in the preceding chapters, the differential diagnosis for surgical neuropathology specimens varies widely depending on the lesion location, imaging characteristics, and patient age. Together, these variables should guide the establishment of pretest probabilities of diagnoses and streamline the interpretation of histologic findings, winnowing numerous distinct entities to a manageable few. Outside of the context of these clues, some CNS lesions with vastly divergent outcomes may differ only very subtly from one another histologically. Simply put, surgical neuropathology cannot be practiced in a vacuum, and the most appropriate diagnosis will only be reached consistently with a disciplined approach that includes input from as much clinical and neuroimaging information as is available.

The following series of tables lists differential diagnoses based on clinical/imaging information (Tables 20-1 to 20-8) and covers most surgical neuropathology specimens but is not intended to be exhaustive.


Approach to Histologic Diagnosis

After establishing a differential diagnosis based on age and neuroimaging, microscopic examination in surgical neuropathology progresses in an algorithmic fashion, starting with a determination of whether the tissue is normal. This can be a daunting task in some cases where the histologic findings are minimal, as in some lower-grade infiltrating gliomas. Abnormal tissue can then be categorized into one of several general pathophysiologic processes, such as reactive/inflammatory, infectious, or neoplastic, from which more specific diagnoses are developed. Another approach is to separate lesions by overall low-magnification pattern, such as circumscribed, infiltrative, perivascular, and leptomeningeal, which to some
extent recapitulates neuroimaging data. Regardless of approach, systematic histologic evaluation for all entities consistent with a particular lesion’s clinical/imaging features is encouraged and will help to prevent inadvertent omission of the correct diagnosis from consideration.








TABLE 20-1 Tumors of the Posterior Fossa








Pediatric
   Pilocytic astrocytoma
   Medulloblastoma
   Ependymoma
   Infiltrating astrocytoma (brainstem)
   Atypical teratoid/rhabdoid tumor
   Dermoid cyst
   Hemangioblastoma
   Embryonal tumor with multilayered rosettes
   Rosette-forming glioneuronal tumor
   Ganglioglioma
Adult
   Metastasis
   Meningioma
   Hemangioblastoma
   Subependymoma
   Infiltrating astrocytoma
   Dysplastic cerebellar gangliocytoma (Lhermitte–Duclos disease) (rare)
   Rosette-forming glioneuronal tumor (rare)
Cerebellopontine angle
   Schwannoma
   Meningioma
   Epidermoid cyst
   Choroid plexus papilloma
   Endolymphatic sac tumor








TABLE 20-2 Lesions of the Spine










Intramedullary spinal cord
   Poorly-circumscribed
     Infiltrating astrocytoma
     Sarcoidosis or other inflammatory process
     Reactive changes around syrinx or kyphosis
   Well-circumscribed
     Ependymoma
     Hemangioblastoma (typically dorsal)
     Pilocytic astrocytoma (often cystic)
     Metastasis
     Demyelinating lesion
     Abscess
     Germinoma (rare, can also be infiltrative)
Intradural, extramedullary
   Meningioma
   Schwannoma
   Neurofibroma
   Malignant peripheral nerve sheath tumor
   Solitary fibrous tumor/hemangiopericytoma
   Calcifying pseudoneoplasm of the neuraxis
   Ependymoma (rare)
   Melanocytoma (rare)
Epidural
   Metastasis
   Herniated intervertebral disc
   Plasmacytoma
   Abscess
   Calcifying pseudoneoplasm of the neuraxis
   Bone and soft tissue tumors
Cauda equina, filum terminale
   Myxopapillary ependymoma
   Schwannoma
   Neurofibroma
   Meningioma (sometimes clear cell)
   Malignant peripheral nerve sheath tumor
   Paraganglioma of the filum terminale
   Metastasis

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Oct 22, 2018 | Posted by in NEUROLOGY | Comments Off on General Approach and Differential Diagnosis
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