Fibroma of Tendon Sheath: A Tumor of Myofibroblasts

Abstract

A clinicopathologic study of 18 cases of fibroma of tendon sheath included an immunohistochemical survey of 7 cases and an electron‐microscopic examination of one. The age of the patients ranged from 1 to 77 years, with a median of 34 years. The most common site of the tumors was the finger (7 cases), followed by the knee (3), the hand (2), and the foot (2). The median greatest diameter of the tumor was 2 cm. The tumors were attached or closely related to the tendon or tendon sheath, and usually well circumscribed, and multinodular or tabulated. Microscopically, spindle or stellate tumor cells with fuchsinophilic cytoplasm were embedded in a dense fibrous stroma with scattered small blood vessels. Most tumor cells have immunoreaction products for actin in the cytoplasm with accentuation along the cell membrane. Ultrastructurally, many of the tumor cells proved to be myofibroblasts.

USP6 genetic rearrangements in cellular fibroma of tendon sheath

“…2 Subsequently, a handful of small series of fibroma of tendon sheath have confirmed the benign behavior of these lesions and the (myo)fibroblastic nature of the constituent cells, both by ultrastructural and immunohistochemical analysis. [15][16][17][18][19][20] Although cases of cellular variants have been reported in almost all series, Pulitzer et al 21 and Smith et al 16 excluded nodular fasciitis-like examples from their respective series, arguing that such cases should be considered examples of tenosynovial nodular fasciitis rather than variants of fibroma of tendon sheath.…”

Fibroma of tendon sheath of the hand: Clinical and pathological study

“…Ultrastructurally, the tumour cells show a cytoplasm containing prominent rough endoplasmic reticulum with dilated cisternae (7,15,19). Also observed were large numbers of free ribosomes, but only occasional mitochondria (15,19).…”

“…Factor VIII antibody staining outlines the endothelium of the tumour's vasculature (16). Unlike schwannomas, in which schwann cells stain with S100 protein antibody, FTS stains negative with S100 protein; therefore, FTS can be differentiated immunohistochemically from a schwannoma (7). It may also be differentiated from malignant sarcomas by a lack of marked cellularity, pleomorphism and abnormal mitotic figures (21).…”

“…The present series shows a similar distribution of cases, from the fingertips to the wrist (Table 1). FTS has been reported in the feet (6), especially on the plantar aspect, and in the lateral aspect of the knee (7).…”

“…Also observed were large numbers of free ribosomes, but only occasional mitochondria (15,19). An electron microscopic study showed the cells of FTS to be identical to myofibroblasts, containing characteristic microfilament bundles with focal, dense bodies (7).…”