“A very unusual case of recurrence of desmoplastic fibroblastoma”: a case report

Abstract

Introduction:

Desmoplastic fibroblastoma is a rare benign soft-tissue tumor which is typically painless and slow-growing, commonly found in the extremities. Despite its benign nature, recurrence is rare, and it generally shows favorable outcomes.

Case Summary:

A 34-year-old male first noticed a painless, slow-growing mass on his left lower back 4 years ago. Two years ago, he underwent a wide local excision of the mass, which was diagnosed as desmoplastic fibroblastoma. However, the mass recurred and progressively enlarged over time. He presented again with the recurrent mass, which was excised a second time. Histopathological examination confirmed the recurrence of desmoplastic fibroblastoma.

Discussion:

Desmoplastic fibroblastoma usually has an excellent prognosis, with no reported recurrences. However, in this case, recurrence was observed, which is uncommon. The recurrence may be attributed to factors such as incomplete excision due to the tumor’s difficult location or inherent biological characteristics of the tumor cells. This rare occurrence warrants further investigation into potential contributing factors for recurrence.

Conclusion:

This case highlights the rare recurrence of desmoplastic fibroblastoma following initial excision. While the tumor generally has an excellent prognosis, this recurrence emphasizes the importance of long-term follow-up.

Introduction

Desmoplastic fibroblastoma (DF), also known as collagenous fibroma, is a rare, benign soft-tissue tumor that was first described by Evans in 1995. In 1996, it was renamed to better reflect its histopathological characteristics, particularly the dense collagenous stroma and the predominant fibroblastic proliferation observed upon microscopic examination^[1]. Typically presenting as a painless, slow-growing mass, it mostly occurs in the extremities^[2]. It has a benign nature with no reported case of recurrence in the literature.

Method

This work has been reported in line with SCARE 2025 criteria^[3].

Case Summary: A 40-year-old man with no known comorbidities presented to the surgery OPD with a painless swelling over the left lumbar region for 4 years. The swelling was not associated with color changes or discharge. It gradually increased in size and restricted movement in the lumbar region. There was no history of trauma, cough impulse, or similar swellings in other body parts. He mentioned a previous similar swelling of around 4 cm × 4 cm for which he underwent marginal excision at a local hospital without histopathological examination. The patient stated that there were no complications at the previous surgery, and the mass was excised completely, as evidenced by the complete disappearance of the visible swelling. However, within 6 months, a small swelling appeared at the surgical site, which grew to approximately 15 cm × 15 cm.

HIGHLIGHTS

• Desmoplastic fibroblastoma (DF) is a rare, benign tumor commonly affecting males, typically in the upper extremities.

• DF usually presents as a painless, slow-growing, non-tender mass, and although it exhibits benign behavior, its slow growth may lead to delayed detection.

• Although DF generally has an excellent prognosis, recurrence in this case highlights the importance of long-term follow-up.

• MRI and histopathology are essential for diagnosis, differentiating DF from other soft tissue tumors.

• This recurrence underscores the need for careful surgical excision and continued monitoring.

On physical examination, the mass was firm, located in the left lumbar region, non-tender, and appeared fixed subcutaneously (Fig. 1). No lymphadenopathy or additional swellings were found. Ultrasonography revealed heterogeneous echogenicity at the left lumbar region, suggestive of a soft tissue mass, prompting a Contrast-enhanced computed tomography (CECT). The CECT showed a well-defined, predominantly soft tissue-density lesion with fat density and calcifications, likely a liposarcoma (Fig. 2). A core needle biopsy confirmed a hypocellular proliferation of stellate fibroblasts infiltrating skeletal muscles and adipose tissue.

Figure 1.

Clinical image showing ill-defined swelling in left lumbar region (white circle).

Figure 2.

CECT abdomen and pelvis showing well-defined, encapsulated (white arrow), predominantly soft tissue density lesion with hypodense area of fat density and multiple foci of coarse calcification anteriorly abutting transversus abdominis and erector spinae muscle and posteriorly abutting left latissimus dorsi muscle.

Surgery was planned for tumor recurrence, and a wide local excision was performed, keeping in mind to prevent further recurrences. Complete removal was assumed intraoperatively as the mass was well circumscribed and lobulated (Fig. 3). The healthy-appearing tissue was removed along with the suspected tumor. The tumor had also invaded the fascia of the latissimus dorsi muscle, so the fascia was also removed along with a thin layer of latissimus dorsi muscle. Hemostasis was maintained, and a drain was placed. The cut surface revealed a large, variegated mass with bony areas and a gritty texture, without hemorrhage or necrosis (Fig. 4).

Figure 3.

Excised mass.

Figure 4.

Excised mass after surgery showing cut section of mass.

Histopathological examination showed a collagenous stroma with dilated blood vessels, no nuclear atypia, or mitotic figures (Fig. 5-8).The patient recovered well postoperatively and was discharged on the 6th day. He was followed up on the 8th day for drain removal. He is regularly kept under follow-up on an OPD basis. No local recurrence was observed during a 10-month follow-up.

Figure 6.

Histopathology image showing collagenous stroma (black arrow) with entrapment of congested blood vessels.

Figure 7.

Histopathology image showing entrapment skeletal muscle (broad arrow).

Figure 5.

Histopathology image showing entrapment of adipose tissue (black arrow).

Figure 8.

Histopathology image showing entrapment of congested and dilated blood vessels (green arrow).

Discussion

Desmoplastic fibroblastoma predominantly affects males, with a male-to-female ratio of approximately 2.5:1. The tumor typically presents between the ages of 16 and 83 years, with a median age of diagnosis around 50 years. DF is most commonly found in the upper extremities, including the arm, shoulder, forearm, and hand, though it can also be present in the lower limbs and back. It has been occasionally observed in the feet. However, the tumor’s occurrence in the tongue, palate, or neck is extremely rare, making these presentations atypical^[1].

Clinically, desmoplastic fibroblastoma typically presents as a painless, slow-growing mass that may persist for an extended period. The tumor is often described as a firm, mobile, and non-tender subcutaneous lesion. Although it can arise in various anatomical locations, DF most frequently affects the upper arm, shoulder, and upper back. In some cases, it may involve deeper structures such as fascial and skeletal muscle tissue. Despite its benign nature, the tumor’s slow growth and non-tender nature can lead to delayed detection. DF exhibits a benign behavior, with no reported cases of recurrence or metastasis in the literature, which reinforces its generally favorable prognosis^[2,4,5].

Analysis of desmoplastic fibroblastoma imaging revealed that radiography, ultrasound, and CT lack specificity, while MRI provides more characteristic findings. Magnetic resonance imaging (MRI) was advised, but the patient denied it due to financial issues.

On MRI, the tumor typically appears as a well-defined, lobulated, ovoid, or spindle-shaped mass closely associated with dense connective tissue. T1-weighted images show low to intermediate signal intensity, becoming more heterogeneous on fluid-sensitive sequences, with lower intensity corresponding to T1 findings. Contrast-enhanced imaging is particularly valuable, frequently showing peripheral and septal enhancement with variable homogeneous enhancement, aiding in diagnosis. The primary differential diagnoses for desmoplastic fibroblastoma include desmoid-type fibromatosis and low-grade fibromyxoid sarcoma, both requiring more aggressive treatment. Key distinguishing features include well-circumscribed margins and peripheral and septal enhancement on imaging, unlike the infiltrative growth and collagenous bands of fibromatosis or the fluid-like signal of myxoid sarcoma^[6].

The recommended treatment approach is a conservative surgical excision^[5]. Grossly, Desmoplastic fibroblastomas of soft tissue are well-circumscribed, rounded, or oval lesions, characterized by a smooth external surface^[1]. Microscopically, desmoplastic fibroblastomas are well-circumscribed, hypocellular tumors with dense fibrosis and fibromyxoid areas, containing sparsely arranged spindle or stellate fibroblasts. Nuclear atypia, necrosis, mitoses, and prominent vasculature are absent^[7]. Stellate-shaped fibroblasts are the key histological feature of this tumor^[8]. The differential diagnosis for desmoplastic fibroblastoma includes various fibrous proliferations and spindle cell neoplasms, such as nodular fasciitis, fibromatosis, low-grade fibromyxoid sarcoma, and benign fibrous tumors. Nodular fasciitis is more cellular, with a loose, myxomatous stroma, and typically affects younger individuals. The hypocellular regions and haphazardly arranged stellate fibroblasts distinguish desmoplastic fibroblastoma from fibromatosis, while dermatofibromas exhibit more organized fibrous proliferation^[7]. The immunohistochemical findings suggest that the tumors are of fibroblastic origin. The diffuse positivity for vimentin, along with focal smooth muscle actin and factor XIIIa expression, supports this inference. The lack of expression for markers such as S-100, HAM, actin, desmin, and CD68 further reinforces the diagnosis, as these markers are typically associated with other cell types and neoplasms^[1,7]. The strong and diffuse nuclear immunoreactivity for FOS-like antigen 1 (FOSL1) serves as a key distinguishing feature of desmoplastic fibroblastoma.

Its presence helps differentiate desmoplastic fibroblastoma from histological mimics such as fibroma of the tendon sheath and desmoid-type fibromatosis, which lack FOSL1 staining. Therefore, FOSL1 staining is a valuable diagnostic tool, especially in small biopsy specimens, aiding in the accurate identification of desmoplastic fibroblastoma^[4]. Immunohistochemistry was not performed in our case due to unavailability in our institute and financial constraints for sending samples to other centres.

Desmoplastic fibroblastoma is generally associated with an excellent prognosis, with no reported recurrences and a maximum follow-up of 12 years^[1]. Marginal excision has an insufficient surgical margin to reduce the local recurrence of desmoid-type fibromatosis^[9]. However, in our case, recurrence of desmoplastic fibroblastoma was observed, which is an atypical occurrence and highlights the need for further investigation into the factors that may contribute to its recurrence, like the difficult location of the tumor leading to incomplete excision or other biological characteristics of the tumor cells.

Conclusion

Desmoplastic fibroblastoma generally has an excellent prognosis with rare recurrence. However, this case presents an atypical recurrence, highlighting the potential challenges of complete excision in difficult anatomical locations. Further research is needed to understand factors contributing to recurrence, such as tumor biology or surgical limitations, despite its typically benign behavior and favorable outcome in most cases.

Strength

Though typically non-recurrent, this case report presents a rare recurrence of desmoplastic fibroblastoma. No similar case reports have been reported in the literature.

Limitation

Though MRI is the preferred imaging modality for DF, it was not performed in our case due to financial constraints. There was no documentation of the initial surgery, so the details of the initial surgery relied on patient recall. We could follow up for a period of 10 months, which is relatively short.

Ethical approval

Not required for case reports as per our institutional review committee in our Institution.

Consent

Written informed consent was taken from the patient, which can be made available on reasonable request.

Sources of funding

The author(s) declare that no financial support was received for the research and/or publication of this article.

Author contributions

S.K.C.: resources, writing original draft, writing review and editing. S.T.: conceptualization, investigations, resources, supervision. S.G.: data curation, formal analysis, project administration, writing original draft. S.K.C.: conceptualization, data curation, project administration, resources, visualization. B.K.: conceptualization, methodology, writing review and editing. Y.A.: data curation, investigations.

Conflicts of interest disclosure

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Guarantor

Dr. K.C. Suraj.

Research registration unique identifying number (UIN)

Not applicable for case study.

Provenance and peer review

Paper was not invited. It is “not commissioned, externally peer-reviewed’’.

Data availability statement

Data is available upon reasonable request.