Paediatric malignant peripheral nerve sheath tumor with osteoid, rhabdomyosarcomatous, and liposarcomatous differentiation

CW Devadoss¹, AR Rau¹, S Manjari², MK Hasaf¹,  
¹ Department of Pathology, M.S. Ramaiah Medical College and Teaching Hospital, Bangalore, Karnataka, India
² Paediatric Surgery, M.S. Ramaiah Medical College and Teaching Hospital, Bangalore, Karnataka, India

Correspondence Address:
Dr. C W Devadoss
Department of Pathology, M.S. Ramaiah Medical College and Teaching Hospital, Bangalore, Karnataka
India

Full Text

Sir,

Malignant peripheral nerve sheath tumors (MPNST) are uncommon spindle-cell sarcomas, originating from a peripheral nerve or exhibiting nerve sheath differentiation, comprising 4-10% of all childhood soft tissue sarcomas. [1]

A 14-year-old male presented to us with dyspnoea and pain and weakness of the upper-left limb. On examination, there was ptosis, miosis, enophthalmos of the left eye and left supraclavicular fullness. A thoracic CT scan revealed a heterogeneously enhancing mass in the left paravertebral region and upper-left thorax measuring 9.6 × 8.2 × 10 cm with associated lytic lesions in D4, D5, and D9 vertebra. The radiologist reported it as malignant posterior mediastinal mass - possibly ganglioneuroblastoma with skeletal metastasis. On left thoracotomy, a fleshy-lobulated tumor originating from the sympathetic chain was seen and complete piecemeal tumor resection was done. Microscopy revealed a fasciculated mitotically active (22/10 hpf) spindle-cell tumor with densely cellular areas, hypocellular myxoid areas and areas of necrosis. Focal osteoid differentiation (7%), rhabdomyosarcomatous (Rms) differentiation (6%), and liposarcomatous (Lps) differentiation (3%) were identified [Figure 1]. Immunohistochemistry revealed intense S 100 positivity in the spindle cells and Myo D1 nuclear positivity in rhabdomyoblasts [Figure 2]. The final diagnosis of MPNST with divergent osteoid, rhabdomyosarcomatous and liposarcomatous differentiation, FNCLCC grade 2, pT2bNoM1, Stage IV was then made. The patient received radiotherapy, 3 DCRT up to 30 fractions in 6 weeks. Subsequently he developed additional spinal metastasis and succumbed to the disease, 6 months after diagnosis.{Figure 1}{Figure 2}

Pediatric MPNSTs have a strong association with Neurofibromatosis Type 1 (NF1) and in this setting have a strong predilection for young males. [1],[2] However, our patient was a young male who did not have any of the National institute of health diagnostic criteria for NF1. [2] A majority of these tumors occur in the extremities, trunk, and head and neck. [3],[4] A posterior mediastinal location and origin from sympathetic chain with clinical presentation as Horner syndrome, is distinctly unusual. About 15% of MPNSTs, especially those associated with NF1, exhibit focal divergent heterologous differentiation commonly into Rms, osteogenic, and cartilaginous elements, illustrating the pluridirectional differentiation capacity of neuroectodermal tissue. [1],[3] Rms differentiation is the most frequent and is associated with poorer prognosis. [3] Lps differentiation is very rare with only five prior reported in the specialized literature. [3],[4],[5],[6] All these cases occurred in the third to seventh decade with our case being the first, in the pediatric age. Simultaneous divergent heterologous differentiation along three or more lineages, as the current case is also very rare with only a few previous reports. [4] It is important to identify the heterologous elements as these have prognostic and therapeutic significance. Whether presence of Lps differentiation alone or in conjunction with Rms differentiation confers a worse prognosis, these rare tumors require further evaluation.

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