1 Introduction

Soft tissue masses are often benign, appearing 100 times more frequently than malignant soft tissue sarcomas.¹ According to the 2020 World Health Organization classification, soft tissue tumors are divided into eleven categories: adipocytic, fibroblastic and myofibroblastic, so-called fibrohistiocytic tumors, vascular tumors, pericytic tumors, smooth muscle tumors, skeletal muscle tumors, gastrointestinal stromal tumors, chondro-osseous tumors, peripheral nerve sheath tumors, and tumors of uncertain differentiation.² Among these eleven categories, soft tissue masses are further subdivided as benign, intermediate, or malignant based on their biological behavior.^2,3 Only 14 % of all soft tissue sarcomas present in the upper limb (except epithelioid sarcomas), and 40–50 % of them originate from the forearm and finger.^4–6 Soft tissue sarcomas of the hand are aggressive and associated with high rates of local recurrence and poor overall survival.⁷ Therefore, research studies have largely focused on their predictors, outcomes, and management. Still, benign soft tissue masses are much more prevalent and can impose significant complications, especially if their size becomes large enough to cause compression of nearby neurovascular structures. Aside from potentially impacting limb functioning, soft tissue tumors residing on an exposed, high-contact surface of the upper extremity may be vulnerable to repetitive injury or trauma that can increase the risk of bleeding, rupture and infection.

Determining which soft tissue masses warrant further work-up and initial surgical intervention via excisional biopsy can be difficult. Many soft tissue tumors go unrecognized as they are asymptomatic. They do not get proper medical evaluation because patients and clinicians alike may be unconcerned by them. Criteria that should increase clinical suspicion of soft tissue sarcoma include: masses that are golf ball size or larger (>5 cm), rapid increase in size, deep location, difficulty mobilizing the mass, and lump recurrence after previous excisional biopsy.⁸ MRI can delineate the etiology of a soft tissue mass and extent of the primary tumor in relation to other anatomical structures. However, biopsy of the mass is the only reliable method to pinpoint the exact tissue of origin and the presence or absence of any malignant cells. Establishing the histopathological diagnosis is critical for treatment planning, as unplanned and inappropriate soft tissue mass excisions can alter prognosis. The aim of this retrospective study is to highlight outcome predictors of hand and upper limb soft tissue swellings. Additionally, we seek to increase awareness among treating physicians and to establish a management strategy for upper extremity (UE) soft tissue masses with predictors that worsen the outcome.

2 Methods

Ethical approval for this study (Ethical Committee N° UKM PPI/111/8/JEP-2023-926) was provided by the Research Ethics Committee of Universiti Kebangsaan in Malaysia on 22 February 2024 with the need for written informed consent waived. All surgically biopsied upper limb soft tissue masses in two tertiary hospitals in Malaysia from 2020 to 2021 were thoroughly evaluated. Bone tumors, arthritic deformities, osteophytes, highly suspicious tumors suggestive of malignancy, and swelling on other parts of the body such as the neck or upper chest were excluded from the review. Data were gathered from the patients’ admission charts, hospital paper and digital archives, as well as Department of Pathology archives after ethics committee approval from Hospital Universiti Kebangsaan Malaysia. A total of 70 patients were included in the study.

The demographic and clinical characteristics of all patients were compiled. Data such as the size and site of the tumor, diagnosis, and complications were recorded. Complication was defined as mass rupture, recurrence, infection, and/or impaired limb function at presentation or following surgery or misdiagnosis affecting the treatment plan. If no significant complication was noted, the outcome was considered satisfactory.

The collected data were analyzed using R 4.2.3 (R Core Team, 2023), RStudio (R studio Team, 2023), and the tidyverse and dplyr packages (Wickham, 2023). Fisher's Exact Test was used to identify association of the outcomes (complication or malignancy) with certain tumor characteristics such as painful or painless swelling, size of the tumor, site of the tumor, and histological diagnosis. A p-value of <0.05 was considered significant.

3 Results

Patient demographics and characteristics of the UE soft tissue masses analyzed are listed in Tables 1 and 2, respectively. In our study, UE soft tissue masses were most prevalent in the 19–40 years age group. The overall male:female ratio was 2:3. Among the cases, 17 % presented with pain and swelling and the remaining 83 % cases presented with only swelling. Most soft tissue masses (90 %) were <5 cm in size and over an exposed surface (91 %) of the upper limb with the majority (64 %) located on the digits. Of all the UE soft tissue masses, 97 % were benign in origin and 84 % presented with a satisfactory outcome. The top three most common histological diagnoses were granuloma (20 %), followed by ganglion cyst (16 %), and giant cell tumor of the tendon sheath (14 %) (Fig. 1). Of the eight patients presenting with complications, none had malignancies (0 %), two had tumors <5 cm (25 %), and seven (88 %) were located on an exposed surface (Table 3). The most common benign soft tissue mass associated with complications was granuloma (33 %). There were only two (3 %) malignant UE soft tissue tumors noted in this series: a rhabdomyosarcoma and a malignant schwannoma, also known as a malignant melanotic nerve sheath tumor (Table 4). Both patients were female and presented with painless swelling. Neither experienced short-term post-operative complications. Incisional biopsy was performed to diagnose the rhabdomyosarcoma. Due to its size and invasion into surrounding neurovascular structures, a complete excision was not possible. Excisional biopsy confirmed the diagnosis of malignant schwannoma, which was originally thought to be an epidermoid inclusion cyst. Both patients were referred to oncology for further management. On Fisher's Exact test, tumor size≥5 cm was a statistically significant predictor of complications (p-value = 1.00e-07) but not malignancy (Table 5). Confirmed tumor diagnosis was also another predictor for complication and malignancy (p-value <0.05). However, tumor site on an exposed surface, type of complaint (swelling vs. pain and swelling), and location on the UE (arm/forearm, hand/wrist, or finger) were not statistically significant predictors for complication or malignancy.

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Fig. 1 Distribution of the histopathological diagnoses of upper extremity soft tissue masses in this study. The top three diagnoses were granuloma, ganglion cyst, and giant cell tumor.

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4 Discussion

Primary malignancies of the upper extremity are rare. One retrospective study spanning 11 years analyzed patients diagnosed with one or more suspected benign upper extremity tumors and evaluated by a hand surgeon. The authors identified three confirmed malignancies among 1606 UE tumors.⁹ Of these, 1593 (99 %) were suspected benign tumors.⁹ Zyluk et al. performed a statistical and histological analysis of 246 upper extremity soft tissue or bony tumors, excluding suspected ganglion cysts, foreign bodies, arthritic deformities, osteophytes, and highly suspicious tumors suggestive of malignancy. Only two malignancies, both fibrosarcomas (0.8 %), were identified post-operatively.¹⁰ In their series, approximately half of the lesions were localized to the digits, and the most common histological diagnoses were giant cell tumor of the tendon sheath (23 %), lipoma (16 %), and epidermoid cyst (9 %).¹⁰ In our study, ganglion cysts and giant cell tumors were the second and third most highly encountered soft tissue swellings, respectively. This is consistent with observations reported in the literature that ganglion cysts are the most common UE tumor, followed by giant cell tumors of the tendon sheath.^9,11–15 One possible explanation as to why granuloma was the most common diagnosis in our series analysis is that many of our patients were manual laborers and were more likely to have trauma and/or foreign body related reactions.^7,14,16 Similarly, epidermoid cyst was the fourth most prevalent soft tissue tumor diagnosis in our study, and these cysts are often caused by traumatic implantation of epidermal cells into the dermis. It has been reported that epidermoid cysts comprise 4 %–14 % of all hand tumors, with carpenters, tailors, and other manual laborers at possible increased risk of developing them.^12,17 Overall, our histologic frequency distribution was most similar to that of Irmak et al., who performed a retrospective analysis of 426 benign, surgically excised soft tissue tumors in Turkish patients and found that pyogenic granuloma (25 %), ganglion cysts (15 %), and giant cell tumors of the tendon sheath (15 %) were the three most common diagnoses.¹⁸

Pain was assessed as a potential predictive variable because some UE soft tissue masses may only present with pain due to non-visible, deep-seated swelling. Benign masses such as hamartomas and glomus tumors can present without swelling, and up to 15 % of soft tissue sarcomas develop within the subcutaneous tissue.^19,20 In general, upper extremity tumors, benign and malignant, tend to be painless.^{9,12,19,21–24} An exception is malignant peripheral nerve sheath tumors in neurofibromatosis type 1 patients which can cause radicular pain.^19,25 Interestingly, in a retrospective review of 101 patients, ganglion cysts accounted for 54 % of the soft tissue tumors but 66 % of these ganglion cysts were painful despite the fact that ganglion cysts are generally accepted to be asymptomatic.^14,15,26 In our cohort of patients, the presence or absence of pain was a poor predictor of both complications and malignancy.

Presence on an exposed surface was a variable studied to understand whether tumors located laterally (arm), dorsally (forearm and hand), or in other high-contact locations (palmar hand, ulnar border of small finger, radial border of index finger and thumb) would be more likely to encounter environmental trauma and therefore become prone to complications. In their retrospective review of 186 patients surgically treated for hand tumors, Fujibuchi et al. found that benign soft tissue tumors arose almost equally among the digits versus the hand/wrist. The thumb was the most common location of soft tissue tumors among the fingers (30 %) while more lesions were identified on the palmar (73 %) versus the dorsal (22 %) aspect of the hand.²¹ Although not statistically significantly predictive in our retrospective analysis, soft tissue swellings over an exposed surface do affect treatment and management, as they can be cosmetically concerning to the patient and can increase the risk of infection, rupture, or bleeding from repetitive injury.

Worrisome features concerning for malignancy include rapid enlargement of a soft tissue swelling, deep location, rest or night pain, and size exceeding 4 or 5 cm in greatest dimension.^19,27–29 In a study of 108 adult patients with UE soft tissue sarcoma, the median tumor size was 6 cm, however, 55 % of the malignant UE soft tissue tumors were <5 cm.³⁰ Collin et al. found that the size of operable, nonmetastatic soft tissue sarcomas was not significantly associated with complications such as local recurrence.²² Our results demonstrated that UE soft tissue tumor size≥5 cm is predictive of complication(s) but not malignancy. Given our small sample size, exclusion of highly suspicious malignancies from the cohort, and overall low prevalence of UE soft tissue sarcomas in the general population, tumor dimension was not statistically significantly associated with malignancy.

The location of soft tissue sarcomas in the upper extremity varies, with 50 % occurring in the shoulder/upper-arm, 30–40 % in the elbow or forearm and 10–20 % in the wrist or hand.^28,30,31 Fujibuchi et al. identified 11 malignant soft tissue tumors in 186 patients and observed that 82 % occurred on the palm or dorsal hand while only two cases occurred in the fingers.²¹ Our results indicated that most of the soft tissue tumors were located on the digits (64 %), however, tumor location was not a predictor of complication or malignancy.

Rhabdomyosarcoma and malignant schwannoma were the only two malignancies identified in our analysis. Another one patient was diagnosed radiologically as liposarcoma, however, histopathology confirmed lipoma. That tumor was >5 cm is size and located on the arm. The most commonly reported UE sarcoma histological subtypes in the literature include malignant fibrous histiocytoma, synovial sarcoma, leiyomyosarcoma, liposarcoma, myxofibrosarcoma, and rhabdomyosarcoma.^21,30,32 In general, epithelioid and synovial sarcomas are the most common soft tissue sarcomas found in the hand.²⁷

No consensus exists on the treatment of benign UE soft tissue tumors.⁹ However, surgical intervention can be considered according to the Enneking staging system used to assess benign soft tissue neoplasms. Non-malignant UE tumors are classified as latent, active, or aggressive based on radiographic interpretation of the tumor margins.^32,33 Well-demarcated lesions are considered latent while UE tumors with indistinct borders are aggressive.^32,33 Latent tumors often do not require surgical management because they remain unchanged or heal spontaneously.³⁴ Benign, active soft tissue tumors continue to grow but are constrained by anatomic boundaries and can be managed by surgical intralesional or marginal excision. Because benign but locally aggressive tumors grow progressively beyond their natural anatomic boundaries, complete surgical excision may be required to prevent local invasion and destruction of nearby structures.

Malignant soft tissue sarcomas can also be staged according to the Enneking system using a combination of surgical grade (low or high), local extent (intracompartmental or extracompartmental), and presence or absence of metastasis. Compared to the TGNM (primary tumor, histologic grade, regional lymph node involvement, presence of metastasis) staging system proposed by the American Joint Committee on Cancer Staging (AJCC), Enneking staging considers anatomic planes and compartments, making it suitable for surgical planning. However, it does not account for primary tumor size, which is considered in the AJCC staging as an important prognostic factor.³³

From our series analysis, it appears that benign UE soft tissue masses≥5 cm are statistically significantly associated with complications including rupture, recurrence, infection, impaired limb function, and misdiagnosis affecting definitive treatment. Therefore, a reasonable approach toward managing large, benign UE soft tissue masses is to surgically excise them sooner rather than later, not only for the purpose of post-excision histopathology, but also to prevent further complications.^3,35,36 A complete surgical excision is important, as the risk of recurrence increases without it. Giant cell tumors of the tendon sheath have a local recurrence rate of 4–50 %.^10,11,27,37 Ganglion cyst recurrence is as high as 40 %^27,38 and is greater than 50 % if only punctured and aspirated.^17,39 Pyogenic granuloma is also prone to recurrence if any residual tissue is left.¹⁸ Complete excision of tophaceous gout is difficult and often unfeasible due to lack of encapsulation.³⁴ However, tophi can be surgically debulked for improved function, enhanced cosmesis, pain relief, impending skin breakdown, and control of drainage or infection.³⁴ Other indications for surgical excision of a benign soft tissue swelling include pain, compression to neurovascular structures, interference with daily activities of living, and aesthetic concerns.¹⁷

5 Conclusion

Upper extremity soft tissue masses are often benign in origin. The most common diagnoses for UE soft tissue masses include ganglion cysts, granulomas, and giant cell tumors of the tendon sheath. UE soft tissue tumor size≥5 cm is a significant predictor of complications such as rupture, recurrence, infection, impaired limb function, and misdiagnosis affecting treatment (p-value <0.05). However, tumor size is not predictive of malignancy. Given the increased risk for complications, suspected benign tumors≥5 cm in greatest dimension should be managed with complete, surgical excision for both diagnostic and therapeutic purposes whenever possible. Other indications for surgical excision of a benign soft tissue mass include locally aggressive growth, cosmetic concerns, and impaired limb function. A suspicion of soft tissue sarcoma warrants further evaluation with MRI, diagnostic core needle biopsy, and early referral to a specialized center with a multidisciplinary sarcoma team that can perform adequate initial resection.

CRediT authorship contribution statement

Lauren Fang: Data curation, Formal analysis, Methodology, Visualization, Writing – original draft, Writing – review & editing. Shalimar Abdullah: Data curation, Writing – review & editing. Kirollos Tadrousse: Data curation, Writing – original draft, Writing – review & editing. Jamari Sapuan: Data curation, Writing – review & editing. Ahmed Suparno Bahar Moni: Conceptualization, Project administration, Supervision, Writing – review & editing.

Ethical statement

Ethical approval for this study (Ethical Committee N° UKM PPI/111/8/JEP-2023-926) was provided by the Research Ethics Committee of Universiti Kebangsaan in Malaysia on 22 February 2024 with the need for written informed consent waived.

Guardian patient statement

Ethical approval for this study (Ethical Committee N° UKM PPI/111/8/JEP-2023-926) was provided by the Research Ethics Committee of Universiti Kebangsaan in Malaysia on 22 February 2024 with the need for written informed consent waived.

Funding sources

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.