Tissue Pathology Online
Reactive Fibrous Proliferation
Pathology of Proliferative Fasciitis and Proliferative Myositis
These benign lesions affect older patient than nodular fasciitis (rarely occurs in children).
The lesions may occur either in superficial soft tissue (proliferative fasciitis) or in skeletal muscle (proliferative myositis).
Proliferative fasciitis is common in the extremities, specially in the
lower limb. Proliferative myositis is common in shoulder girdle and upper
Proliferative myositis is a poorly defined scar-like lesion involving muscle and overlying fascia.
In both conditions, there are clusters of rounded basophilic fibroblasts with prominent nuclei and nucleoli (ganglion-like) which blend with areas showing usual features of nodular fasciitis.
However, the stroma is more myxoid and fibrinoid areas may be present.
In proliferatiive myositis an additional feature is poorly demarcated fibroblastic proliferation involving the epimysium, perimysium and endomysium in a checkerboard-like fashion.
Immunohistochemistry reveals that the ganglion- like cells express vimentin and lack actin or desmin.
Immunohistochemistry and electron microscopy confirm the mixed fibroblastic and myofibroblastic nature of these lesions.
Images of Proliferative Myositis:
Carcinoma, melanoma or large cell lymphoma in adults .
Rhabdomyosarcoma and even ganglioneuroblastoma in children.
These entities are separated by clinical appearance and by immunohistochemistry.
Acral myxoinflammatory fibroblastic sarcoma is a low grade sarcoma of extremities which can involve joints and tendon sheaths.
This multinodular tumour consists of fibrous areas with marked inflammation, vacuolated cells and mononuclear or binucleated Reed-Sternberg-like cells.
Fasciitis (Atypical Decubital Fibroplasia)
Ischemic fasciitis was first
described by Montgomery et al (abstract
) in 1992 as atypical
decubital fibroplasia and was subsequently termed ischemic fasciitis by
Perosio and Weiss (abstract)
The patient usually has a short history of 3 weeks to six months.
Lesions are located
in the deep subcuti and occasionally extended into the muscle. Extensive
epidermal epidermal ulceration is absent.
The spindle cells are focally atypical with large hyperchromatic nuclei, prominent nucleoli and basophilic cytoplasm resembling those of proliferative fasciitis.
Fat necrosis is seen at the periphery.
Immunohistochemistry: Two thirds are actin positive, and half are CD34 positive. Desmin is negative.
1. Decubitus ulcer has more extensive ulceration overlying granulation tissue without zones of necrosis, a myxoid stroma or atypia.
2. Proliferative fasciitis lacks the zonal architecture , vascular features and peripheral granulation tissue.
3. Epithelioid sarcoma is subcutaneous with central necrosis but in more discrete nodules and cytologically bland and epithelial markers are positive.
4. Myxoid malignant fibrous histiocytoma lacks the zones and is more pleomorphic and cellular with a typical vascular pattern.
5. Acral myxoinflammatory fibroblastic sarcoma has inflammation, large polygonal cells with prominent nucleoli and myxoid nodules with vacuolated fibroblasts.
6. Myxoid chondrosarcoma is multilobular and has more uniform bland cells , often in a lace-like pattern, a hyaluronidase-resistant, more myxoid and less necrotic stroma with haemorrhage, glycogen in cells and S100 protein positivity.
7. Myxoid liposarcoma has a striking vascular pattern with lipoblasts and is extremely rare in the subcutis.
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