3. Methods (differential diagnosis, investigations and
treatment)
After a thorough history and physical examination, we had a number of
differential diagnoses, namely, hematoma, cyst, chronic abscess and
neoplastic growths like rhabdomyosarcoma, soft tissue sarcoma, etc. The
T1w Magnetic Resonance Imaging (MRI) of pelvis showed a 6.3x9.5x8 cm
sacral mass, with heterogenous post-contrast enhancement, as shown in
figure 1. There was diffuse cortical break with associated large
extraosseous soft tissue mass, with involvement of spinal canal and
exiting sacral nerve roots. Bilateral gluteal muscles were involved,
with greater involvement on the right side. The presacral extension
displaced the rectum anteriorly without any bowel invasion. Few
subcentimetric indeterminate pelvic nodes were noted. The possible
differentials now were sacral chordoma and sacral teratoma. Biopsy taken
from the lesion revealed a poorly differentiated chordoma with
fibrocollagenous tissue infiltrated by tumor arranged in sheets.
Individual cells were pleomorphic, round to oval with coarse chromatin,
prominent nucleoli and abundant eosinophilic to clear cytoplasm. There
were foci of calcification with ~8/10hpf mitotic figures
and no necrosis. On immunohistochemistry (IHC), tumor cells stained
positive for AE1/AE3 and brachyury and negative for SOX10, S-100, and
desmin. The histological and IHC images have been illustrated in figure
2. 18-fluorine-fluorodeoxyglucose positron emission tomography/computed
tomography (18F-FDG PET) CT was done for metastatic work-up, and showed
a 9 mm, FDG avid nodule in upper lobe of left lung, with maximum
standardized uptake value (SUVmax) being 4.58.
The patient’s sacral lesion was deemed unresectable in view of large
size and potential sacral instability as well as loss of bladder and
bowel control post resection. CT-guided biopsy from the left upper lobe
confirmed poorly differentiated metastatic chordoma, with lung
parenchyma and fibro collagenous tissue infiltrated by tumor cells
arranged in sheets and focal cords. Tumor cells exhibited moderate
pleomorphism, round to oval hyperchromatic nuclei, inconspicuous
nucleoli, eosinophilic to vacuolated cytoplasm. Focal myxoid change and
focal areas of necrosis were identified. On IHC, tumor cells stained
positive for Brachury (diffuse), AE1/AE3 (diffuse), S-100(focal) and
negative for CK7, Napsin A and TTF1. The intent was kept curative as the
single metastatic lesion was small and was found amenable for both
radiofrequency ablation (RFA) and surgery. He was planned for definitive
radiotherapy (RT) to the sacral region. During planning CT scan, the
skin overlying the lesion was inflamed and impending ulceration, and the
patient was unable to lie flat in supine position for adequate
immobilization, so he had to be simulated in prone position using
four-clamp abdomino-pelvic thermoplastic cast and five mm bolus on the
skin overlying the lesion. The RT planned was for 72 Gray (Gy) in 40
fractions, 1.8 Gy daily fractions, five days a week using volumetric
modulated arc therapy (VMAT). However, the lesion had clinically
appreciable local progression between the simulation and starting of
treatment. The local skin appeared even more inflamed, both in intensity
and extent, so the RT plan already made had to be aborted and adaptive
replanning was considered, with same setup as before. On account of the
rapid progression of the primary lesion, an extended planning CT scan
covering whole thoracic region was taken. It showed multiple metastatic
nodules in both the lungs, the largest being 1.8x1.7 cm in the left
upper lobe. With this, the intent of treatment was changed to palliative
and the plan for RFA was deferred. He had already received 22Gy in 11
fractions, out of the planned dose. Further palliative intent RT of 12Gy
in 2 fractions, 6Gy weekly fractions, was delivered to the local site
for palliation of pain. The child has now been receiving symptomatic
palliative treatment under the pain and palliative department of our
hospital.