Mesenchymal hamartomas are rare, benign osseous tumors that
typically involve the rib cage and present during the first year of
life1-9.
Aggressive growth is not part of the natural history, and surgical excision is
generally curative. Fewer than fifty cases have been reported in the
literature to date. To our knowledge, there have been no reports of this tumor
originating in the cervical spine.
The lesion appears expansile on radiographs and often causes deformity of
the chest wall and ribs. It may be lobulated, is primarily cartilaginous, and
may contain bone trabeculae. Although most of these lesions are benign,
malignant transformation has been
reported5.
We present a case of a primary mesenchymal hamartoma that occurred in the
cervical spine of a young adult. The patient was informed that data concerning
this case would be submitted for publication.
A nineteen-year-old woman presented to her family physician with a
one-month history of a mass at the base of the left side of the neck. The mass
was associated with local discomfort as well as with local radiation of pain
into the shoulder and neck. The patient was a full-time student in
voice-training and had noticed dysphonia during the month prior to
presentation. The patient also reported intermittent dysesthesias in the left
arm and the dorsum of the left hand. No other neurological complaints were
noted, and the remainder of the medical history was noncontributory. There
were no systemic symptoms.
Physical examination revealed a firm, fixed mass at the base of the
posterior (subclavian) triangle of the left side of the neck. The mass was
posterior to the sternocleidomastoid muscle and was palpable just cephalad to
the medial third of the left clavicle. The mass appeared fixed and was not
tethered to over-lying muscular structures. The mass was not pulsatile and was
without erythema, warmth, bruit, or substantial tenderness.
Neurological examination revealed grade-4 (of 5) weakness of the left
triceps and long finger extensors. The left triceps reflex was diminished but
present. Sensory dysesthesia was present over the dorsum of the long, ring,
and little fingers of the left hand and was particularly noticeable with
pin-prick testing. Swallowing was unimpeded, and the motor function of the
sternocleidomastoid and trapezius muscles was normal. Pulses were symmetrical
in the upper extremities. Adson's maneuver and Wright's test were negative.
The remainder of the neurological examination revealed normal findings.
Imaging
Plain radiographs revealed an osseous expansile mass that appeared to
originate from the left C7 transverse process
(Fig. 1).
A computerized tomographic scan showed a mass, measuring 3 × 5 cm,
that appeared to originate from the left C7 transverse process. The osseous
cortex was expanded but intact (Fig.
2), and osseous septations were noted in the mass. The lesion was
adjacent to the left first rib but was separate and distinct from the rib.
A magnetic resonance imaging scan confirmed the location of the mass
between the scalenus anterior and scalenus medius muscles
(Fig. 3). The tumor displaced
the transverse cervical artery and the brachial plexus anteriorly.
The differential diagnosis included giant-cell tumor, aneurysmal bone cyst,
osteochondroma, and, less likely, chondrosarcoma or osteosarcoma.
Prior to definitive treatment, the case was discussed at an
interdisciplinary oncology conference where the treatment alternatives were
considered. The mass was thought to be a benign active (stage-II) lesion
according to the staging system of Enneking et
al.10. Because of
the benign radiographic appearance of the lesion, a biopsy was not performed
and a definitive single-stage wide excision was planned. On the basis of our
preoperative planning, the possibility of a marginal excision, specifically
where the tumor displaced the vertebral artery and the brachial plexus, was
considered.
Excisional Biopsy
The lesion was initially exposed through an anterior and posterior surgical
approach. Through a transverse left-sided anterior cervical incision and after
an initial dissection medial to the left carotid sheath, the left vertebral
artery was identified and dissected free of the medial portion of the mass.
Dissection through the longus colli facilitated exposure of the origin of the
tumor from the C7 transverse process and allowed for an osteotomy of the
process and separation of the tumor from its origin. Dissection lateral to the
carotid sheath allowed the brachial plexus to be identified as it was draped
over the ventral aspect of the tumor. After careful dissection, it became
clear that the tumor could not be delivered anteriorly through the brachial
plexus.
Therefore, a posterior left paramedian exposure was performed and a portion
of the left first rib was resected in order to facilitate exposure and
ultimate removal of the tumor. The tumor was adjacent to the rib but was not
attached to it. The tumor was then delivered, en bloc, through the posterior
exposure.
Postoperatively, the neurological findings were unchanged. At six months
postoperatively, the patient reported that her voice had returned to normal,
without the preoperative dysphonia, and a neurological examination revealed
normal findings. At four years postoperatively, follow-up computerized
tomographic scanning revealed no evidence of recurrence of the tumor.
Pathological Findings
The gross specimen was a hard nodule, measuring 5 × 3 × 2.5 cm,
that was covered by an intact thin fibrous membrane. The cut surface of the
mass revealed convoluted, white chondroid tissue with small amounts of
intervening gritty, soft, red tissue (Fig.
4). Histologically, the mass was composed predominantly of lobular
hyaline cartilage (Fig. 5). The
cartilage was hypocellular, and the chondrocytes were bland and lacked
cytologic atypia or mitotic activity. Between the nodules of cartilage was
cellular, highly vascular tissue that contained uniform bland spindle cells
and abundant dilated blood vessels of varying sizes
(Fig. 6). Scattered trabeculae
of woven bone and osteoclast-like giant cells also were evident. The margins
of the mass were well defined, and there was no evidence of infiltrative
growth into the adjacent normal tissue. The surgical margin was wide.
Mesenchymal hamartoma is a rare tumor that has not previously been
described as originating from the spine or, more specifically, from the
cervical spine in an adult.
Mesenchymal hamartoma most commonly presents as a chest-wall deformity,
respiratory compromise, or pneumothorax in an infant or as an incidental
finding on a chest radiograph. Presentation may occur at the time of birth or
shortly thereafter. There have been reports of this tumor being detected in
utero6. The features
of this lesion are usually those of an aggressive, expansile lesion that most
commonly originates from a rib. Fine-needle aspiration has assisted in the
diagnosis of these
tumors6,9.
Surgical resection is the optimal treatment and has been associated with a low
rate of
recurrence3,5.
One case of malignant transformation has been
reported5. To our
knowledge, we are the first to report a case of mesenchymal hamartoma
originating from the spinal column.
In the case of our patient, the clinical and imaging findings suggested
compression as opposed to invasion of the caudal roots of the brachial plexus.
Standard principles of oncological care suggested that a biopsy should be
performed prior to excision, but it was the consensus opinion at our oncology
conference that an excisional biopsy would minimize the risks of recurrence
and would not compromise the patient's care.
Given the age of the patient, the location of the tumor, and the expansile
nature of the lesion, the initial differential diagnosis focused on benign
primary tumors of the spine, specifically, aneurysmal bone cyst and giant-cell
tumor. The surgical pathological diagnosis of mesenchymal hamartoma was
unexpected.
In conclusion, this unusual tumor should be added to the differential
diagnosis of posterior element primary spinal tumors. These tumors may
encroach upon adjacent neural and vascular structures, causing symptoms in
addition to local pain. Wide surgical resection appears to have resulted in
successful treatment in this case. ?