Nuchal Fibrocartilaginous Pseudotumor in a 10-Year Old Girl.
REPORT OF A CASE
The patient was a 10-year-old girl who was hit by a car 4 years earlier. She presented with pain and discomfort in the posterior aspect of the neck and required an orthopedic collar for 3 weeks. Subsequently, the complaints disappeared. Four years later, she developed a 2.5-cm, firm nodule that appeared at the C5-6 level and that was painless and not attached to the bone. Linear tomography of the neck showed no detectable abnormalities; however, a computed tomographic scan of the neck showed a 1.5-cm nodular thickening of the nuchal ligament at the C5-6 level, without calcifications (Figure 1). The lesion was resected, and 1 year later, the patient remains well and has no evidence of recurrence.
[Figure 1 ILLUSTRATION OMITTED]
The excised nodule consisted of fibrocartilaginous tissue surrounded by dense connective tissue of the nuchal ligament (Figure 2). The central area showed a fibrocartilaginous matrix, with chondrocytes that were small and lacked nuclear enlargement or nucleoli (Figure 3). Neither mitotic figures nor binucleated chondrocytes were found. Under polarized light, the extracellular matrix contained abundant polarizing collagen in a somewhat disorganized fashion; the elastic tissue stain showed scarce fragmented elastic fibers in the center of the nodule. At the periphery, abundant elastic fibers were apparent. There were no calcifications, hemosiderin deposits, or inflammatory infiltrate.
[Figure 2-3 ILLUSTRATION OMITTED]
In the soft tissues, many nonneoplastic conditions can produce the clinical appearance of a mass; some of them are secondary to inflammatory processes, trauma, or foreign material and others correspond to amyloid deposition or heterotopic distrophic calcification. Still others are due to proliferating fibrous tissue, which can be confused with true neoplastic conditions.
The nuchal fibrocartilaginous pseudotumor described by O'Conell et al is a lesion with a characteristically specific location in the posterior aspect of the nuchal ligament, at its attachment to the deep cervical fascia, in the midline at the level of C4-5 or C5-6. Histologically, the lesion consists of a poorly delineated, moderately cellular fibrocartilaginous nodule, with cracks within the collagen-rich matrix. The chondrocytes within the mass are small and lack nuclear enlargement or nucleoli. Mitotic figures and binucleated chondrocytes are absent. At the interface of the nuchal ligament with the fibrocartilaginous mass, the ligamentous tissue appears degenerated, with fragmentation of the elastic fibers. The adjacent paraspinal muscles and overlying superficial fascia are histologically normal without interstitial scarring or hemosiderin deposits.
A lesion that can occur in this area is a so-called nuchal fibroma. However, this lesion is not confined to the midline, lacks an association with ligaments, and occurs superficial to the fascia. The histologic picture corresponds to sheets of hypocellular dense collagen, with interspersed mature fat, small vessels, and entrapped nerve fibers; since it is not composed of fibrocartilage, it resembles more of a fibrolipoma, lipomatosis, scar, or elastofibroma.
Other entities that show cartilaginous tissue, which are not characteristically located in the cervical region but which should be taken in to account for the differential diagnosis, are as follows. The soft tissue chondroma presents with well-defined lobules of hyaline cartilage, usually in association with a tendon or a tendon sheath and most commonly in the distal extremities. The synovial chondromatosis may occasionally present as a soft tissue mass in relationship to a synovial-lined joint and is characterized by lobules of hyaline cartilage with an overlying synovial membrane. The mesenchymal chondrosarcoma shows an obviously malignant undifferentiated component with small blue cells, in addition to areas of low-grade hyaline cartilage. The extraskeletal myxoid chondrosarcoma is also a malignant deep soft tissue mass, in which fibrocartilage is not a feature. The calcifying aponeurotic fibroma has a predilection for the distal extremities; the cartilaginous component is microscopic and embedded within a fibromatosis-like background. Myositis ossificans may have fibrocartilage but is also accompanied by a reactive spindle cell component, with woven bone in various stages of maturation. Other entities, such as the calcifying fibrous pseudotumor and the fibromatosis, do not have a fibrocartilaginous component.
Crockard et al described 5 elderly patients with space-occupying lesions, within the anterior aspect of upper spinal canal, posterior to the odontoid, resembling degenerating intervertebral disk, which compressed the upper spinal cord. However, the localization was not in the nuchal area. In addition, pathologically the masses were composed of a mixture of degenerated ligament tissue, fibrocartilage, necrotic material and fibrin, with calcification and vascular ingrowth, The authors speculated that the masses probably arose from an exuberant repair reaction after partial tears of the transverse ligament of the odontoid process.
The nuchal ligament is an anatomic structure made of a fibroelastic membrane that extends from the occipital bone to the spine of the seventh cervical vertebra. Scapinelli described in this ligament the formation of sesamoid bones, developing in connective tissue with a previous stage of fibrocartilaginous metaplasia. He considered that this change is secondary to mechanical factors, acting during the neck flexion, when the thick nuchal ligament is subjected to pressure and trauma as it passes over the spinous processes of the cervical vertebrae.
O'Connell et al considered that trauma at the C4-5 or C5-6 level, which is more susceptible to hyperflexion injuries during deceleration events such as automobile crashes, generates a process of fibrocartilaginous metaplasia, which in turn produces a pseudotumoral mass in this particular
site. The range of time between the trauma and the onset of the lesion is variable, from 27 years to 2 months. The case described by Lewinnek and Peterson had no history of trauma, all the previous reported cases have been in adults, and we did not find any report of this condition in children. The clinicopathologic findings in our pediatric case were similar to the ones described in the nuchal fibrocartilaginous pseudotumor.
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Accepted for publication December 1, 1999.
From the Departments of Pathology (Dr Luevano-Flores) and Orthopedic Surgery (Dr Aguirre-Madrid), Hospital Clinica del Parque, Chihuahua, Mexico.
Reprints: Eduardo Luevano-Flores, MD, Morelos 1407-B, Colonia Centro c.p. 31000, Chihuahua, Chihuahua, Mexico (e-mail:firstname.lastname@example.org).