Ulcerated nodular fasciitis of the finger mimicking soft tissue sarcoma: a case report

Abstract

Nodular fasciitis (NF) is a benign, self-limiting myofibroblastic proliferation that often mimics soft tissue sarcoma because of its rapid growth, hypercellularity, mitotic activity, and local infiltration. NF typically arises in the forearm, trunk, or upper arm, whereas finger involvement is extremely rare, accounting for 0–2% of cases. Ulceration or protrusion is even more unusual and may further resemble aggressive malignancy. We report a rare case of ulcerated NF of the finger, clinically mimicking a fungating sarcoma. A 26-year-old Japanese woman presented with a rapidly enlarging ulcerated mass on the ulnar side of the right middle finger. MRI revealed an isointense lesion on T1-weighted images and hyperintense signal on T2-weighted and T2 fat-suppressed images. Core needle biopsy showed spindle-cell proliferation in a loosely storiform pattern within a fibromyxoid stroma, with vascular fibrinoid necrosis and neutrophilic infiltration. Immunohistochemistry demonstrated smooth muscle actin positivity and negativity for CD34 and S100. Fluorescence in situ hybridization confirmed USP6 gene rearrangement, supporting the diagnosis of NF. Because of progressive growth after biopsy, marginal excision with full-thickness skin grafting was performed under local anesthesia, achieving complete removal and functional preservation. Histopathological findings were identical to those of the biopsy specimen. The postoperative course was uneventful, and there was no recurrence at the final follow-up, with full finger mobility maintained. This case highlights a rare manifestation of NF with ulceration in the finger, an entity that can closely mimic high-grade sarcoma. Awareness of this presentation and the use of molecular confirmation of USP6 gene rearrangement are crucial for accurate diagnosis and avoidance of unnecessary radical surgery, particularly in functionally and cosmetically critical locations such as the hand.

Introduction

Nodular fasciitis (NF) is a benign, self-limiting proliferation of myofibroblasts first described by Konwaler et al. in 1955 [1]. It commonly arises in the subcutaneous tissues of the upper extremities, trunk, and head and neck regions, typically affecting young adults [2, 3]. Despite its benign nature, NF frequently mimics soft tissue sarcoma, both clinically and histologically, because of its rapid growth, hypercellularity, mitotic activity, and infiltrative features [4]. Although NF was initially considered a reactive lesion, recent molecular studies have demonstrated its neoplastic nature, characterized by the rearrangement of the USP6 gene [5–9].

Although NF can be found anywhere on the body, including the forearm (27–29%), back or chest wall (15–18%), and upper arm (12%) [10], those arising from the finger are particularly rare, accounting for only 0–2% of all the NF cases [11, 12]. Moreover, NF rarely causes protrusion or ulceration of the overlying skin, making such presentations highly unusual and difficult to distinguish from soft tissue sarcomas [5].

Here, we report a rare case of ulcerated NF arising in the finger that exhibited locally destructive features closely resembling a fungating soft-tissue sarcoma (Figs. 1, 2 and 3).

Fig. 1.

a–c Magnetic resonance imaging (MRI) obtained at the previous institution. No ulceration was noted at the time. a T1-weighted images. b T2-weighted images. c T2 fat-suppressed images. d, e Physical findings at the time of the initial visit to our hospital. A mass with a protruding ulcer was observed on the ulnar side of the right middle finger

Fig. 2.

a Needle biopsy revealing a loosely storiform proliferation of non-atypical spindled cells in a fibromyxoid background. (hematoxylin and eosin, × 100). b Break-apart FISH for USP6 showing rearrangement with splitting of the green and red signals

Fig. 3.

Marginal excision was performed on the tumor of right middle finger. a A mass was observed on the ulnar side of the middle finger without size change. b Marginal excision was performed. c The resected specimen, which was pathologically diagnosed as nodular fasciitis. d Postoperative appearance of the finger at last follow-up. The skin graft was successfully engrafted, and range of motion was fully preserved

Case report

A 26-year-old Japanese woman presented with a rapidly enlarging ulcerated mass on the ulnar side of her right middle finger. She had initially noticed the lesion one month before the first visit to the local hospital and was referred to our institution because of concern for a malignant soft tissue tumor, as the lesion developed protrusion and ulceration during the interval between her presentation at the local hospital visit and her referral to our hospital. Magnetic resonance imaging (MRI) performed at a previous institution revealed a mass with an isointense signal on T1-weighted images, a hyperintense signal on T2-weighted images, and an uninhibited signal on T2 fat-suppressed images(Fig. 1a-c). No ulcerations were observed. Upon examination at our hospital, the lesion measured approximately 2 cm in diameter and protruded from the ulnar side of the middle finger with ulceration(Fig. 1d, e). Laboratory tests revealed mild inflammatory activity with a white blood cell count of 7300/µL and a C-reactive protein (CRP) level of 0.58 mg/dL.

Given the suspicion of malignancy and the relatively large tumor measuring about 4 cm in diameter, core needle biopsy was performed. Histological evaluation revealed proliferation of spindled cells in a loosely storiform pattern, embedded within a fibromyxoid stroma (Fig. 2a). The lesion exhibited vascular fibrinoid necrosis and neutrophilic infiltration, likely reflective of an overlying ulceration. Immunohistochemical staining showed that the spindle cells were positive for smooth muscle actin (SMA) but negative for CD34 and S100. Fluorescence in situ hybridization (FISH) revealed the rearrangement of the USP6 gene (Fig. 2b). Based on these results, the lesion was diagnosed as NF.

As the lesion continued to enlarge after biopsy, marginal excision with full-thickness skin grafting was performed under digital block as local anesthesia (Fig. 3a-c). Reconstruction was achieved with skin grafting using the medial ankle skin as the donor site, because a small portion of the surrounding skin was excised together with the tumor, and the lesion was located near the PIP joint. Histopathological findings from the excised specimen were identical to those obtained from the biopsy, confirming the diagnosis of NF.

The skin graft successfully adhered to the wound bed and the postoperative course was uneventful (Fig. 3d). At the final follow-up visit, no evidence of recurrence was observed. The patient had no pain or functional impairment of the finger and achieved full range of motion of the finger.

Discussion

This case represents a rare manifestation of NF in the finger, associated with protrusion and ulceration, mimicking a fungating aggressive soft-tissue sarcoma.

Prior to performing the needle biopsy in the present case, our differential diagnoses included pyogenic granuloma, soft tissue sarcomas including epithelioid sarcoma, synovial sarcoma, clear cell sarcoma, etc., and cutaneous or adnexal malignancies. Soft tissue tumors of the digits present a diagnostic challenge because both benign and malignant lesions may appear clinically similar. For example, pyogenic granuloma often grows rapidly with ulceration and bleeding, thereby mimicking malignant tumors [13]. Among sarcomas, epithelioid sarcoma is the most characteristic in the hand. Synovial sarcoma and clear cell sarcoma, though less common, must also be considered [14]. In addition, skin and adnexal cancers may present as protruding or ulcerated digital lesions. Therefore, we performed the core needle biopsy for accurate diagnosis, which revealed nodular fasciitis.

Although NF can be found anywhere on the body, the most common sites of involvement are reported to be the forearm (27–29%), back or chest wall (15–18%), and upper arm (12%) [10]; those arising from the finger are particularly exceptional, accounting for only 0–2% of cases of NF [11, 12].

Clinically, most patients with NF have a history of a rapidly growing mass that has been present for only a few weeks [15], and the current case showed a rapid growth in a month. However, despite rapid growth during the initial stages of the disease, protrusion from the body surface is extremely rare. To the best of our knowledge, only a limited number of NF cases with skin perforations have been reported (Table 1) [16–22]. Of these, five occurred in the upper extremities and three appeared to be triggered by mechanical irritation. In three of the seven reported cases, USP6 FISH analysis was performed, and one case of finger NF was negative for USP6 rearrangement. On the other hand, it has been reported that ulceration occurred in 11 out of 24 cases of intradermal NF; however, no cases occurring in the fingers have been reported in this series [23]. The case described here is unique because the lesion protruded and ulcerated without identifiable external mechanical stimuli.

Table 1.

Reported cases of NF with skin perforation

Reference	Age/Sex	Location	Mechanical irritation	USP6 gene split	Treatment	Recurrence
Sevilla et al. [14]	21/F	hand	+	NA	wide resection	–
Bracey et al. [15]	8/F	arm	+	NA	resection	–
Majidi et al. [16]	25/F	ear	NA	NA	resection	–
Celentano et al. [17]	67/M	tongue	–	NA	resection	–
Kinoshita et al. [18]	15/M	shoulder	–	+	wide resection	–
Sawamura et al. [19]	76/F	hand	–	+	marginal resection	–
Arakawa et al. [20]	16/M	finger	+	−	resection	–
Our case	26/F	finger	–	+	marginal resection	–

Although NF is a benign lesion that typically regresses spontaneously, its clinical features, including rapid growth and local invasiveness, and histological features, including high cellularity and mitotic activity, can pose a major diagnostic challenge, such as tumor location or ulceration, especially in patients with atypical clinical manifestations.

In our case, the histology was consistent with classic NF morphology, showing spindle-shaped cells with loosely storiform growth and hemorrhage, and immunohistochemistry supported myofibroblastic differentiation. Notably, FISH analysis revealed USP6 rearrangement, supporting the diagnosis of NF. USP6 fusion is considered a useful molecular marker for NF, with a sensitivity reported between 83 and 93% and a specificity reaching 100% [7–9] in an appropriate histological context. This molecular finding can help avoid overtreatment such as wide or radical excision, which would otherwise be indicated for suspected high-grade sarcomas[3]. Importantly, USP6 gene rearrangement is not specific to NF. Other lesions, including fibro-osseous pseudotumor of the digits, myositis ossificans, and aneurysmal bone cyst, have also been reported to USP6 rearrangement [24–26]. In the present case, these entities were excluded based on both clinical and histological findings. Taken together, the clinical setting and histology strongly supported a diagnosis of NF rather than other USP6-rearranged tumors.

Considering the continuous growth of the lesion, surgical excision was performed. The patient’s postoperative course was uneventful, with no local recurrence at the final observation and complete preservation of function. This case underscores the importance of accurate preoperative diagnosis in the evaluation of rapidly growing soft-tissue lesions, especially those with sarcoma-like clinical features, to ensure accurate diagnosis and appropriate management.

Here, we present a rare case of ulcerated NF in the finger that clinically mimicked a high-grade sarcoma. Accurate diagnosis was achieved through a combination of histopathology and molecular confirmation of USP6 gene rearrangement. This case highlights the diagnostic challenges posed by atypical NF presentations and emphasizes the importance of accurate preoperative diagnosis in guiding appropriate treatment strategies, thereby avoiding unnecessary radical procedures.

Author contributions

All listed authors contributed to the original manuscript. SS and KO: were the main musculoskeletal oncologists of this case and wrote the manuscript draft. AK: coordinated and completed the manuscript. TT: supported orthopaedic surgical management. TK: supported the management of the plastic surgery. AY: supported histopathological and molecular analyses. All authors have read and approved the manuscript of this case report.

Funding

This study was funded by the National Cancer Center Research and Development Fund (2022-A-15).

Data availability

The data used to support the findings of this study are available from the corresponding author upon request.

Declarations

Conflict of interest

The authors declare that they have no conflicts of interest.

Ethical approval and consent to participate

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee. For this type of study, formal consent is not required.

Consent for publication

Written informed consent was obtained from the patient for the publication of this case report and the accompanying images. No identifiable information was included in this report.