Desmoid Tumor Formation following Posterior Spinal Instrumentation Placement.

Study Design Case report. Objective The objective of the article is to illustrate a case of desmoid tumor (DT) formation after posterior instrumentation of the thoracic spine. Methods A 57-year-old woman presented with lower extremity clumsiness, balance, and ambulation difficulty resulting from spinal cord compression due to an upper thoracic atypical vertebral hemangioma. Ten months after undergoing embolization, resection, and placement of instrumentation for this lesion, the patient developed a growing mass at the rostral end of the incision. Biopsy revealed desmoid fibromatosis. The mass was removed via an en bloc resection. Histology revealed an infiltrative DT above the laminectomy site abutting the instrumentation. Results At 2-year follow-up, there was no evidence of recurrence of the tumor. Conclusion Paraspinal DTs have been reported in the literature to develop after surgical procedures of the spine. Often times, patients attribute swelling or fullness at the site of their surgery to scar tissue formation or instrumentation. One must consider the possibility of a DT in the setting of reported surgical site fullness or mass after spine surgery. It is thought that postoperative inflammation present in the surgical bed may promote formation of DTs. Instrumentation may also contribute to inflammation and increase the likelihood of developing a DT. Generous margins must be taken to prevent recurrence.

Introduction

Desmoid tumors (DTs), also known as aggressive fibromatoses, are characterized as rare, slow-growing tumors. Although strictly benign, they are locally invasive with a high rate of recurrence even after seemingly total resection.1 DTs typically develop sporadically, often in the abdomen, hip/buttocks area, and shoulder girdle. Some populations are at higher risk, including individuals with episodes of antecedent trauma at the site of the tumor.2 A particularly rare subset of these cases includes DTs that develop adjacent to the spinal column. A total of five reported cases have described this phenomenon in the absence of Gardner syndrome, a variant of familial adenomatous polyposis (FAP), or any other predisposing genetic diseases.3 4 5 6 7

This report describes an instance of postoperative aggressive fibromatosis that developed 10 months after corpectomy and spinal fusion for treatment of an atypical vertebral hemangioma in the thoracic spine.

Case Report

A 57-year-old woman presented with lower extremity clumsiness, balance, and ambulation difficulty resulting from spinal cord compression due to an upper thoracic atypical vertebral hemangioma. The patient underwent embolization followed by resection (Fig. 1). The resection involved a transpedicular approach for a T4 corpectomy, placement of an expandable cage extending from T3 to T5 and instrumented posterior fixation from T2 to T7. The patient made a good recovery from the uncomplicated procedure.

Fig. 1

Preoperative images depicting the original hemangioma. (A) Sagittal computed tomography (CT) demonstrating the hemangioma in the T4 vertebral body (arrow). (B) Axial CT at the T4 vertebral level.

Ten months postoperatively, the patient reported moderate pain at the rostral end of the surgical incision. A mass reported by the patient to have enlarged was found on palpation, just superior to the surgical incision. As the mass continued to grow, the patient suffered from increasing local pain and pressure, but there were no neurological deficits.

Magnetic resonance imaging (MRI) revealed a 5.7 × 1.6 × 3.1 cm T2 hyperintense mass within the right subcutaneous tissues and paraspinal muscles at the T1–T3 levels (Fig. 2). The mass was located superficial to a pedicle screw at the rostral end of the fusion construct. The tumor was removed via an en bloc resection. Negative margins were achieved through added removal of the spinous processes of T1–T2 and part of C7. The fully excised tumor was measured to be 4.5 cm in diameter.

Fig. 2

Magnetic resonance images (MRI) showing the postlaminectomy desmoid tumor (DT) and results after surgical excision. (A) Preoperative sagittal STIR MRI showing the DT (arrow). (B) Preoperative axial T2-weighted MRI of the same tumor (arrow). (C) Postoperative sagittal T2-weighted MRI demonstrating absence of tumor. (D) Postoperative axial T2-weighted MRI demonstrating absence of tumor.

The firm rubbery mass was in some areas histologically compact and appeared to exclude preexisting elements. Elsewhere was infiltrative and trapped skeletal muscle fibers and adipose tissue. The tumor was composed largely of dense collagen and fibroblasts. The degrees of cellularity and cytological atypia varied from region to region, but both were low in most areas. In a few regions, however, there was a modest degree of cytological atypia and low-level mitotic activity. Mitoses were absent in paucicellular, more fibrotic areas (Fig. 3). Immunostaining for β-catenin was confined to the cytoplasm in most cells, but there were scattered cells in which nuclei were also positive.

Fig. 3

Hematoxylin and eosin stain of the desmoid tumor. (A) The paucicellular, somewhat fascicular and lobular mass incorporates regional tissues such as skeletal myocytes (40×). (B) Cell density here is low and there is only slight-to-moderate cytological atypia. Other, more cytologically atypical, areas were somewhat more cellular. Myocytes are trapped in the infiltrating lesion (100×).

Serial MRI was performed to follow for tumor recurrence. At 2-year follow-up, there has been no evidence of recurrent disease. The patient has done well and is back to work as a nurse educator.

Discussion

Aggressive fibromatosis comprises 0.03% of all neoplasms and less than 3% of all soft tissue tumors.2 Several conditions such as FAP and other hereditary cancer syndromes predispose individuals to developing these fibroblastic growths.8 A summary of the five previously reported cases of DT formation soon after laminectomy in patients without a unique predisposing condition are presented in Table 1.3 4 5 6 7

Table 1

Summary of present previously reported postoperative spinal desmoid tumors

Author	Age/Sex	Location of laminectomy	Original condition	Instrumentation	Neurological deficit	Location of tumor	Treatment
Gonatas 19613	45 F	Cervical	Intervertebral disc	None	None	Adherent to rhomboid and levator scapulae and scapula	Excised in entirety
Wyler and Harris 19737	39 F	C6-T1 hemilam.C8-T2 dorsal rhizotomy	Dysesthesia in left elbow with radiation to forearm	No	None	Paraspinous muscles	En bloc after recurrence
Lynch et al 19995	49 F	T9-T11	Thoracic meningioma	None	Nonea	Paraspinous	Surgical resection with wide margins
Güzey 20064	50 F	L4-L5	Spondylolisthesis	Yes	None	T12, L1 spinous processes, Rostral margin	Total resection with 1 cm safety margin
Sevak et al 20126	48 F	C6-T1	Extradural schwannoma	Yes	Nonea	Subcutaneous	Wide local excision with right trap; myocutaneous flap reconstruct
Current	57 F	T4	Vertebral hemangioma	Yes	None	SubcutaneousRostral Margin	En bloc resection

Some mild postoperative (procedure before development of desmoid tumor) paresthesias or weakness.

The studies are listed chronologically.

When comparing these cases, it is clear that there are striking similarities. All cases occurred in adult women ranging in age from 39 to 50 years, with our patient, a 57-year-old woman, having similar demographics. This is concordant with previous studies that have asserted that 67 to 80% of all DTs arise in women, with 50% between the ages of 30 to 50 years. It has been previously suggested that aggressive fibromatosis may be hormonally related.2 In fact, middle-aged mothers may be at heightened risk because of characteristic hormone profiles.

In addition, none of the five previous cases developed neurological deficits as a result of the DT. Two patients did have mild residual neurological side effects as a result of the initial laminectomy procedure, but these symptoms were unrelated to the DT. Our patient was similarly neurologically asymptomatic.

The number of reported cases of paraspinous aggressive fibromatosis cases occurring postlaminectomy indicates that this may not be as rare of a phenomenon as originally suspected. The scar tissue surrounding a laminectomy may be predisposed to neoplastic transformation due to underlying inflammation from both the treated malignancy and tissue manipulation from surgery.

Studies have elucidated some of the mutations that lead to sporadic DTs. Recent studies have demonstrated that sporadic DTs often have mutations in adenomatosis polyposis coli and β-catenin genes. A study by Lazar et al demonstrated that 85% of sporadic DTs have mutations in the CTNNB1 gene, which encodes β-catenin. Furthermore, different CTNNB1 mutations were associated with differing rates of progression and recurrence.9

β-catenin has been observed to play a significant role in postfracture bone healing. A study by Chen et al demonstrated that β-catenin signaling is activated during bone healing. Furthermore, resultant T cell factor-dependent transcription is only activated in later stages of repair, after mesenchymal cells have differentiated into fibroblastic cells.10 This would suggest a unique molecular and cellular environment within the surgical bed during both the acute and chronic stages of healing. Inflammatory cytokines unregulated at both these time points likely can potentiate DT growth. Theoretically, any bone fracture has the potential to trigger DT growth that could explain the development of aggressive fibromatosis after clavicle and radius fractures.

DTs are often difficult to treat because of their proliferative nature and capacity for local invasion. Treatment becomes even more challenging when these masses are found proximal to sensitive anatomical structures, such as in the spine. In the presented case and five others, gross total resection with negative margins was elected. This was seen to be the best option given the high local recurrence rate associated with positive margin resections (54% over 10 years) as compared with those with negative margins (27% over 10 years). If the mass were located proximal to functionally important anatomic entities such that negative margins were impossible to achieve, adjuvant radiation therapy (25% recurrence over 10 years) would have been another option.1

Conclusion

Middle-aged women undergoing laminectomies have been observed to develop postoperative DTs of the spine. Although these tumors do not cause neurological deficits, they tend to be locally invasive and are best treated with wide excision with negative margins.

Although it has been speculated that hormonal triggers could be involved in postsurgical DT formation, it is also likely that inflammatory cytokines released in the surgical bed during the acute and chronic phases of healing also play a role in growth of aberrant tissue. This may be particularly true with the continued presence of surgical instrumentation for fixation, which represents foreign material within the surgical bed.