Lipomyelomeningocele with Intraspinal Cartilaginous Choristoma: A Rare Case of Heterotopic Mesenchymal Differentiation

Abstract

Lipomyelomeningocele (LMMC) is a closed neural tube defect in which neural elements are incorporated into a spinal lipoma. This congenital condition may present at birth as a lumbosacral subcutaneous mass or manifest neurologic symptoms later in life. A choristoma is a tumor-like mass of normal tissue in an abnormal location, most commonly found in the head and neck, and it is exceedingly rare within the spinal canal. We report an 11-month-old female infant with a congenital lumbosacral swelling whose MRI revealed a tethered cord and LMMC with spina bifida at the S2–S3 level. Surgical detethering was performed, and histopathology confirmed LMMC. In addition, a heterotopic cartilaginous choristoma was identified in the excised tissue, an unusual finding in spinal dysraphism. This case highlights a unique example of heterotopic mesenchymal differentiation in spinal dysraphism and adds to the limited literature on intraspinal choristomas.

Keywords

lipomyelomeningocele - choristoma - congenital anomalies

Introduction

Lipomyelomeningocele (LMMC) is a rare form of spinal dysraphism in which a spinal lipoma is blended with neural tissue.[1] It represents a closed neural tube defect that is often associated with a tethered spinal cord. The etiological agents that are implicated are unknown. The prevalence ranges from 0.3 to 0.6 per 10,000 live births.[1] LMMCs protrude dorsally through a spina bifida defect and remain attached to the dorsal surface of the neural placode, often connecting with subcutaneous fat. Most commonly, they arise in the lumbosacral region and present in females within the first 6 months of life, though some cases remain undiagnosed until later in childhood.[1]

A choristoma is histomorphologically an island of normal tissue in an abnormal site. They are usually seen in the head and neck region, and their occurrence in the intraspinal region is sparse but documented. Components may include cartilage, bone, salivary gland, or thyroid tissue. Cartilaginous choristomas are usually described in the distal extremities and rarely in soft tissues of the head and neck.

We report a case of an 11-month-old female infant with spinal dysraphism comprising heterotopic cartilaginous differentiation within an LMMC, a finding that adds to the limited literature on this variability of mesenchymal elements in neural tube defects.

Case Presentation

An 11-month-old female infant presented with a progressively enlarging congenital swelling in the lumbosacral region since birth. The infant was active, feeding well, and had no history of systemic illness, seizures, or hydrocephalus. There were no bladder or bowel symptoms. On clinical examination, vital signs were normal, and limb power was full in all extremities. Local examination revealed a 10 × 10 cm soft, mobile, well-defined mass in the lumbosacral midline without overlying skin changes or discharge.

MRI of the lumbar spine demonstrated the spinal cord ending at the L5 level, consistent with a tethered cord. A spina bifida defect was noted at the S2–S3 vertebrae, through which fat and neural elements were herniating into the dysraphic sac, indicating a closed neural tube defect (LMMC). The imaging findings confirmed the diagnosis of LMMC ([Fig. 1A]). The patient was taken to surgery for excision of the LMMC and detethering of the cord.

Fig. 1 (A) Magnetic resonance imaging (MRI) of the lumbar spine demonstrating spina bifida at the S2 and S3 vertebral levels (red arrow), with herniation of fat and neural elements through the defect. (B) Intraoperative photograph showing swelling over the lumbosacral region. (C) Intraoperative exploration revealing a lipomatous mass attached to the spinal cord.

Operative findings included a 4 × 4 cm lipomatous mass arising from the lower end of the spinal cord just below L5. The distal cord and filum terminale appeared abnormal and tethered, with dysplastic dura. Spina bifida was noted at the L5 and S2–S3 levels with fibrofatty tissue herniating through the defect. Complete excision of the lipoma and detethering of the spinal cord were performed ([Fig. 1B, C]). No complications occurred during surgery or in the immediate postoperative period. Excised tissue was submitted for histopathological examination.

Gross examination of the surgical specimen revealed two separate fibrofatty tissue masses. The larger mass measured 5 × 3 × 3 cm and was gray-brown on the surface, with a 0.6 × 0.5 cm gray-white cartilaginous nodule on cut section. The smaller mass measured 2 × 1 × 1 cm and was gray tan. Histologically, sections from the larger mass showed a well-encapsulated lesion composed of mature hyaline cartilage surrounded by fibrous tissue, mature adipose tissue, blood vessels, and neural elements ([Fig. 2A–C]). The final pathology diagnosis was LMMC with an associated cartilaginous choristoma.

Fig. 2 (A) Well-encapsulated lesion composed of lobules of mature adipocytes (H&E stain; ×100). (B) Meningothelial cells (red arrow) and adjacent nerve bundles (blue arrow) (H&E stain; ×400). (C) Hyaline cartilage surrounded by mature adipose tissue (H&E stain; ×200).

A choristoma is a mass of histologically normal tissue located in an abnormal site, typically present at birth or early childhood. Although most commonly reported in the head and neck region, choristomas can occur in various tissues, including cartilage, bone, salivary gland, or thyroid tissue. Cartilaginous (chondroid) choristomas are often found in the soft tissues of the distal extremities and are rarely seen intraspinally. These lesions grow at the same rate as the surrounding tissue and lack neoplastic behavior, being considered developmental malformations rather than true tumors. Intraspinal cartilaginous choristomas are extremely rare, with only a few cases reported in the literature.

In our patient, histopathology revealed a focal area of mature cartilage within the LMMC, confirming a cartilaginous choristoma. The coexistence of this heterotopic cartilage with an LMMC, along with the cord tethering, makes this a uniquely complex case of spinal dysraphism.

Follow-up and Outcomes

Date	Event
November 5, 2024	Patient admitted with a congenital lumbosacral swelling. Clinical evaluation and baseline investigations were performed.
November 6, 2024	MRI of the spine confirmed tethered cord and lipomyelomeningocele at S2–S3 level. Diagnosis of LMMC with tethered cord was established.
November 7, 2024	Preoperative preparation completed; surgical plan discussed with guardians.
November 8, 2024	Surgical excision of lipomyelomeningocele with detethering was performed. Intraoperatively, a 4 × 4 cm lipomatous mass with cord tethering and dysplastic dura was identified.
November 9, 2024	Excised tissue sent for histopathological analysis.
November 10–11, 2024	Uneventful postoperative recovery. Histopathology reported lipomyelomeningocele with cartilaginous choristoma.
November 12, 2024	Patient discharged in stable condition with advice for regular neurological and developmental follow-up.

At 3 months postoperatively: Infant remained active and playful with no new neurological deficits. Surgical wound healed well, with no CSF leak, infection, or recurrence. Full strength was preserved in all limbs, and bladder/bowel function was normal. Long-term follow-up is planned for tethered cord monitoring.

After 3 months follow-up, the infant was doing well without new deficits. The surgical wound remained well-healed, with no cerebrospinal fluid leak, wound infection, or recurrent swelling. Motor power in all four limbs was preserved, and bladder/bowel function was normal. The patient adhered to medical advice and remained asymptomatic, underscoring a successful outcome.

Discussion

Meningoceles represent herniation of leptomeninges through a dural and bony defect, presenting as a skin-covered sac. When neural tissue such as the spinal cord or cauda equina is incorporated, the lesion is classified as a myelomeningocele.[2] LMMC is a closed neural tube defect wherein neural elements are blended into a spinal lipoma. This anomaly affects approximately 1 to 6 per 100,000 live births.[3] [4]

The abnormality arises from disordered development during both primary and secondary neurulation. In primary neurulation, faulty disjunction between the neural tube and ectoderm allows mesoderm to enter and form a lipoma, distorting spinal anatomy. In secondary neurulation, abnormal mesodermal migration and cavitation can disrupt spinal cord formation. Although less understood, morphogenetic signals such as Sonic Hedgehog and Pax transcription factors are thought to play roles.[4]

Clinically, LMMC, especially in the lumbosacral region, tether the cord at the attachment site, leading to progressive neurological deficits. Excessive neural tissue overgrowth at the site of spina bifida may also impede neural groove fusion, contributing to LMMC formation.[2] [4] Most cases are diagnosed at birth when a fatty midline or paramedian lumbosacral mass is observed, with nearly 48% of patients neurologically intact at presentation.[4] Our case presented similarly with a painless swelling.

MRI is crucial in diagnosis, demonstrating fatty masses, tethered cord, and associated anomalies.[4] In our patient, MRI showed the conus ending at L5, consistent with tethered cord, and spina bifida at S2–S3 with fat and neural elements herniating through the defect, confirming LMMC.

Histologically, congenital spinal lipomatous malformations show immature and mature adipocytes in lobules, fibrous bands, and nerve radicles.[5] In our case, one specimen showed a well-encapsulated lesion composed of hyaline cartilage, fibrous tissue, adipose tissue, vessels, and neural tissue. The smaller mass contained fibrofatty tissue with skeletal muscle, arachnoid cells, nerve bundles, and vessels.

Choristomas are masses of mature tissue in abnormal locations, often detected at birth or early childhood. Although most common in the head and neck, they can contain cartilage, bone, salivary gland, or thyroid tissue.[6] Cartilaginous choristomas usually occur in distal extremities, rarely intraspinally. They are malformations, not true neoplasms, and grow with surrounding tissues.[6] Intraspinal choristomas are extremely rare, with only a few cases reported in literature. Based on currently available literature, only three cases of intraspinal cartilaginous choristoma have been reported to date.[7] [8] [9] Our present case therefore represents the fourth known case and the first reported instance occurring in association with an LMMC. In our patient, histopathology revealed a focal area of mature cartilage within the LMMC, confirming a cartilaginous choristoma. The presence of such a choristoma suggests heterotopic mesenchymal differentiation during neural tube development. This supports the theory that aberrant mesodermal migration or abnormal mesenchymal induction during primary or secondary neurulation may lead to incorporation of cartilaginous tissue within a dysraphic lesion. These lesions are benign and do not alter long-term prognosis; however, their identification is important to avoid misdiagnosis as teratoma or other neoplastic entities. Reporting such rare associations helps expand our understanding of the histological variability and developmental complexity of spinal dysraphism.[7] [8] [9] Thus, our case represents a rare coexistence of LMMC with an intraspinal cartilaginous choristoma, a unique finding expanding the spectrum of heterotopic differentiation in spinal dysraphism.

Conclusion

This case highlights a rare presentation of a lumbosacral LMMC associated with an intraspinal cartilaginous choristoma. The combination of a closed neural tube defect, cord tethering, and heterotopic cartilaginous tissue underscores the complexity of spinal dysraphism and its developmental origins. Early recognition through imaging and timely surgical intervention are crucial to prevent progressive neurological deficits. This case contributes to the limited literature on intraspinal choristomas and emphasizes the importance of thorough histopathological evaluation in atypical spinal masses to guide diagnosis and management.

Conflict of Interest

None declared.

Informed Consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient attenders has given her consent for her images and other clinical information to be reported in the journal. The patient attenders understands that name and initials will not be published, and due efforts will be made to conceal identity. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

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Publication History

Article published online:
03 February 2026