Primitive Neuroectodermal Tumors (PNET ) are rare thoracopulmonary malignancies grouped in the family of small round-cell tumors. There is overlap with the more common Ewing’s sarcoma which occur primarily in children and adolescents. PNET is exceedingly rare in adults with only a few published case reports. We report a case of PNET seen in an adult and discuss the radiographic and histopathological findings.
A 24 year old Armenian male presented with a one month history of cough, fevers, and left sided pleuritic chest pain. He was seen as an outpatient two weeks prior and did not respond to a course of antibiotics. His review of systems was negative and he otherwise had no significant past medical history. The patient was born in Armenia and came to the United States at the age of ten. He denied any prior tobacco use. At initial presentation he was febrile at 39.0 C, BP 120/64, HR 89, RR 20, and O2 sat 98% on RA. Chest auscultation revealed decreased breath sounds at the left base with dullness to percussion. There was a mild leukocytosis with chest roentgenogram revealing a left lower lobe infiltrate and an associated moderate sized pleural effusion. Thoracentesis with ultrasound guidance was attempted with no aspirate. A computed tomography of the chest showed a moderate left pleural effusion with significant heterogeneity and high attenuation; as well as possible nodularity, with nodularity extending along the mediastinal pleura. Transthoracic biopsy disclosed a malignant round-cell tumor positive for CD99 and vimentin. The microscopic features and results from the immunohistochemical studies pointed towards a diagnosis most consistent with PNET. The patient received a second opinion and ultimately had a Video-Assisted Thoracoscopic Surgery (VATS ) biopsy at an outside hospital which revealed the same diagnosis. He subsequently underwent neoadjuvant chemotherapy followed by surgical resection for local control.
Primitive Neuroectodermal Tumors (PNET ) of the thoracopulmonary region are highly aggressive neoplasm’s with a mean survival of eight months. This tumor is seen predominantly in children and young adults and is thought to arise from embryonal cells migrating from the neural crest. Frequently this entity presents as a chest wall mass that may involve the pleura. The neoplasm is an undifferentiated small round-cell tumor which must be distinguished from neuroblastoma, rhabdomyosarcoma, and Ewing’s sarcoma. There is particular overlap with Ewing’s sarcoma which both share a reciprocal chromosomal translocation at (11;22). Positive staining with CD99 and neuron specific enolase with a negative stain for periodic acid Schiff differentiate it from other small round-cell tumors. Prognosis is very poor despite multimodal therapy with wide excision, chemotherapy, and radiotherapy; with a 2 year survival of 38% and a 6 year survival of 14%.
Primitive Neuroectodermal Tumors (PNET ) of the chest wall are particularly aggressive tumors that should be considered in the differential diagnosis of chest wall masses regardless of age. Once diagnosed early wide excision along with chemotherapy and radiation must be undertaken for any hope of long term cure.
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