Acral Myxoinflammatory Fibroblastic Sarcoma, inflammatory myxohyaline tumour of distal extremities with Reed-Sternberg like cells
Definition
The tumour is found across a wide adult age range with an equal gender frequency. Presentation is usually with a slow-growing ill-defined painless mass. The clinical diagnosis is often of a ganglion cysts, tenosynovitis, or giant cell tumors of tendon sheath. The most common site is the hand, particularly the digits or metacarpophalangeal joints followed by the foot, ankle and wrist.
The tumour is typically multinodular and poorly circumscribed. It is often adjacent to or within the joints, or extends along tendon sheaths.
There is usually infiltration of the subcutaneous fat or dermis. The epidermis remains intact. Invasion of skeletal muscle may occur but is limited. There is a marked infiltration of plasma cells, lymphocytes, polymorphonuclear leukocytes and eosinophils. There is frequently focal haemosiderin deposition. Fibrosis varies from granulation tissue to sclerosis. There are myxoid zones or pools of mucin with abrupt transitions from areas of solid tumours. Variable numbers of large atypical cells are seen, some ganglion-like, some multi-vacuolated resembling lipoblasts within the myxoid areas, some resembling Reed-Sternberg cells or virocytes2.
| large pleomorphic lesional cells | |||||||||
| Vimentin | 25/251 | ||||||||
| CD68 | 17/251 | ||||||||
| CD34 | 7/251 | ||||||||
| SMA | 2/251 | ||||||||
| MIB-1 |
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| p53 |
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| S-100 | 0/251 | ||||||||
| HMB45 | 0/251 | ||||||||
| EMA | 0/251 | ||||||||
| AE1/AE3 | 0/251 | ||||||||
The large, pleomorphic lesional cells occur in a background of reactive fibroblasts, myofibroblasts, lymphocytes, plasma cells, and granulocytes: characteristically they have a single, often clefted, nucleus with evenly or irregularly distributed chromatin and one or more very large central or marginal nucleoli. Some have prominent pseudo-inclusions formed by cytoplasmic invaginations. The cytoplasm is richly endowed with rough endoplasmic reticulum, mitochondria, and intermediate filaments, forming a complex network or densely packed perinuclear whorls. Thin filaments of actin type or filament condensations are not seen. Scattered lysosomes, small lipid droplets, and glycogen deposits are observed. SOME bizarre lesional cells reveal numerous intracytoplasmic inflammatory cells, including granulocytes and lymphocytes, some of which showed signs of pyknosis or apoptosis.
There may be overlap with haemosiderotic fibrolipomatous tumour and pleomorphic hyalinizing angiectatic tumour3
Treatment is primarily by surgical excision.
Local recurrence is common. Rarely there may be regional lymph node or lung metastases.
©SMUHT/PW Bishop