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April 2008
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Schwannoma are
slow growing benign nerve sheath tumours. Age: Common in patients between the ages of 20 and 50. Site: These are usually located on the head and neck and flexor surface of upper and lower extremities.The spinal roots, cervical, sympathetic,vagus and ulnar nerves are commonly involved. The deeply located lesions are situated in the retroperitoneum and the posterior mediastinum. Visit: Pancreatic Schwannoma ; Neurogenic Tumours of the Lung Gross:
The tumour is surrounded by true
capsule consisting of the epineurium. Microscopic features:
Schwannomas are usually
solitary, well circumscribed, encapsulated lesions, mostly confined to the
subcutis. Multinodular lesions may be present in the dermis, this is known
as 'plexiform neurilemmoma'. Immunohistochemistry: S100 is strongly expressed by most cells of schwannoma.The cells also express Vimentin and myelin basic protein. Differential diagnosis: Neurofibroma ; Palisaded encapsulated neuroma (more number of axons and Schwann cells in interlacing fascicles together with cleft like spaces.; Cutaneous leiomyoma (smooth muscle actin and desmin positive) ; Palisaded myofibroblastoma ( involve lymph nodes, contain fibroblastic and myofibroblastic cells and are S100 protein negative). (ESCOP) IMAGE LINKS1 ; 2 ; 3 ; 4 ; 5 ; 6 ; 7 ANCIENT SCHWANNOMA
Image
Link1 This is a variant of Schwannoma
displaying prominent degenerative changes. The degenerative changes
include cyst formation, calcification, hemorrhage and hyalinization. (ESCOP) IMAGE LINKS1 ; 2 ; 3 ; 4
CELLULAR SCHWANNOMA This variant is usually found in
the deeper tissues (retroperitoneum or mediastinum). Histologically
,there are compact spindle shaped cells arranged in a fascicular or
whorled growth pattern. Verocay bodies and Antoni B areas are not
conspicuous. Mitotic figures are present (more that 10 per10 high power
fields). The thick fibrous capsule around the tumour shows a dense
lymphocytic infiltrate. (ESCOP) IMAGE LINKS:1 ; 2 ; 3 ; 4
MELANOTIC SCHWANNOMA (ESCOP)IMAGE LINKS:1 ; 2 ; 3 ; 4 This rare variant usually occurs in
middle aged adults and commonly arises from the posterior spinal nerve
roots.
NEUROBLASTOMA-LIKE SCHWANNOMA:
IMAGE
LINKS 1 ;
2
Benign schwannomas may contain rosette-like
structures mimicking neuroblastoma/PNET.
Tumour cells are positive for S100 protein and negative for neuronal
markers synaptophysins and neurofilament protein. MIC2 is negative (rules out PNET type
differentiation).Individual cells were surrounded by type IV collagen.
This is a feature characteristically seen in schwannian but not in
neuronal tumours.
PLEXIFORM SCHWANNOMA: IMAGE LINK(Dr Weems) Plexiform schwannoma may demonstrate conventional, cellular, or mixed appearance. Site:1.Common superficial (dermal and subcutaneous) tumours 2. Deep somatic soft tissue.Worrying histologic features are increased cellularity and mitoses. D/D-Plexiform neurofibromas and malignant peripheral nerve sheath tumour. |
