Introduction

Within the tendon sheath tumours of the upper extremity, the most frequent benign neoplasms are Schwannomas.

Schwannomas are slow-growing tumours that originate from Schwann cells along the nerve sheath. This lesion develops eccentrically to the nerve fibers, being encapsulated by the perineurium. It is usually detected as a solitary lesion, within the age range of 20 to 50 years. Due to its insidious development, diversity of location, and involvement of structures, the definitive diagnosis is often delayed or even misdiagnosed. Different initial diagnostic methods such as magnetic resonance imaging and Doppler ultrasound have been proposed. Although they may share some clinical characteristics, certain specific symptoms of schwannomas suggest their diagnosis and allow for appropriate treatment. The objective is to discuss the clinical, imaging, histological, and immunohistochemical factors to identify nerve tumours of the hand sheath and upper extremities and differentiate them from their malignant counterparts. The literature and the most current recommended surgical techniques for tumour removal are also reviewed.

Case Report

A 32-year-old male with no significant history is presented and comes for evaluation due to a current condition of 24 months of evolution, it begins with an increase in volume, initially asymptomatic and with slow and progressive growth; without clinical follow-up due to the SARS COV2 pandemic. At the time of the examination, a tumour located in the 4th finger of the left hand was evident on the palmar side of the palpable proximal phalanx, solid, firm consistency, with adherence to deep planes, approximately 5x3 cm, capillary refill of fewer than 3 seconds with preserved strength 5/5, paresthesias on the ulnar edge of the same finger. Extension 35 degrees, limitation of metacarpophalangeal flexion function with 120 degrees and proximal interphalangeal 110 degrees of the 4th finger, abduction and adduction of 20 degrees. The study protocol began requesting radiography, USG Doppler, and magnetic resonance imaging of the left hand, as well as preoperative laboratories. In the X-ray of the left hand, in the palmar region of the proximal phalanx of the 4th finger, a radiolucent image with a nodular appearance, with irregular edges, which causes irregularity in the bone cortex, with areas of thinning and deformity due to bone destruction, showing a predominance of affection in its volar aspect. As a final statement, a lytic and expansive tumour is reported in the proximal phalanx of the fourth finger (Figure 1).

Figure 1: X-ray of the left hand, a radiolucent image with a nodular appearance in the phalanx of the 4^th finger.

USG Doppler reports a nodular-looking image in the proximal phalanx of the fourth finger of the left hand, dependent on deep soft tissues, with lobulated but defined edges, heterogeneous content, predominantly hypo-echogenic with dimensions of 30 x 19 x 20 mm, in its longitudinal, anterosuperior, and transverse axes, respectively with an approximate volume of 6.3 CC. The color Doppler application showed predominantly peripheral mixed vascularity dependent on the radial interdigital artery, spectrum was taken in peripheral vessels with systolic velocity up to 45 cm/s and 5 cm/s in the centre. The lesion caused bone remodelling and ulnar displacement of the flexor tendons, recovering their alignment at the level of the middle and distal phalanx. The fibrillar pattern and diameter were preserved within the parameters without evidence of solutions of continuity. The flexor and extensor tendons of normal sonographic characteristics. As a final state, it is reported: A deep soft tissue tumour on the palmar side of the proximal phalanx which, due to its characteristics, suggests hemangioma; intact superficial and deep flexor tendons with ulnar displacement at the level of the proximal phalanx (Figure 2).