Soft tissue Tumors - Fibroma of tendon sheath

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Soft tissue Tumors

Fibroblastic / myofibroblastic tumors

Fibroma of tendon sheath

Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 20 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Well circumscribed, lobulated fibrous tumor attached to tendon or tendon sheath
● Also called tenosynovial fibroma
● Benign, uncommon
● May overlap with nodular fasciitis (Am J Surg Pathol 1989;13:472) or giant cell tumor of tendon sheath (Mod Pathol 1995;8:155, Histopathology 1992;20:213)

Epidemiology
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● 60% men, ages 30-50 years old with nodule on fingers, hands or wrist

Case reports
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● Tumors of palmar flexor sheath (Internet Journal of Hand Surgery 2008;2(1))
● Medial canthus of eye (Ophthal Plast Reconstr Surg 2007;23:341)
● Multiple fibromas of tendon sheath (Ann Dermatol 2011;23:S45)

Treatment
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● Excise to relieve symptoms but preserve function, may be difficult to remove from adherent tendons
● Benign, but up to 24% recur; does not metastasize

Clinical images
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Multiple non-movable deep seated nodules on palm

Gross description
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● Well circumscribed, small fibrous multinodular mass < 3 cm, cut surface is pale, solid and homogeneous

Micro description
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● Well circumscribed nodules of dense fibrous tissue with occasional spindle or stellate mesenchymal cells in S or C shaped patterns
● Cells have scant cytoplasm and elongate nuclei with evenly distributed fine chromatin
● Often dilated or slit-like channels / clefts resembling tenosynovial spaces
● Varies from cellular to paucicellular
● May have bizarre tumor cells, extravasated red blood cells, but no atypical mitotic figures, no necrosis, no hyperchromasia

Micro images
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Multinodular proliferation

Extensive collagenization of nodules produces this typical, eosinophilic, paucicellular
appearance, incomplete separation of the nodules produces cleft-like spaces

Most cases are paucicellular with scattered spindled fibroblasts in a densely collagenized matrix and scattered small vessels

Transition from collagenous to cellular area

Cellular area resembles leiomyosarcoma or fibrosarcoma, but these tumors are rare in hands and feet

Fibroblasts are bland (ruling out sarcoma) and separated by collagen

Predominately acellular fibrous tissue with areas of hyalinization and characteristic slit-like vascular channels

Spindle shaped fibroblasts in collagenous stroma with slit like vascular channels

Cytology images
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Loose cohesive clusters of bland appearing spindle shaped cells with variable cytoplasm and oval/elongated nuclei and hyalinized collagenous fragments

Electron microscopy description
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● Resembles myofibroblasts and fibroblasts

Electron microscopy images
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Spindle cells in collagenous matrix (M) have oval and convoluted nuclei (N),
clefts (C) are present between cells and nuclei

Spindle cell has a convoluted nucleus (N), rough endoplasmic reticulum (RER),
vacuoles (V) and thin band of myofilaments just beneath the plasma membrane (arrows)

Myofilament bundles (M) show periodic densities (arrows)

Spindle cell has rough endoplasmic reticulum (RER), myofilaments (M) and pinocytotic vesicles (arrows)

Positive stains
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● Smooth muscle actin, vimentin

Molecular
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● May have t(2;11)(q31-32;q12) (Histopathology 1998;32:433)

Differential diagnosis
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● Sarcoma: rare in hands and feet, usually large masses with cellularity, marked chromatin abnormalities and abnormal mitotic figures
● Benign fibrous histiocytoma: usually not hands or feet, prominent histiocyte-like cells, foam cells, giant cells and hemosiderin, CD68+
● Giant cell tumor of tendon sheath: more cellular, cells have histiocyte-like nuclei, also prominent giant cells, foam cells, hemosiderin; no slit-like vascular spaces, no extensive hyalinized stroma

Additional references
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● Stanford University

End of Soft Tissue Tumors > Fibroblastic / myofibroblastic tumors > Fibroma of tendon sheath

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