Teaching Case

A 16-year-old previously healthy female patient presents with c/o right-sided chest pain on exertion, breathlessness and weight loss with low-grade fever and generalised weakness. She then was investigated further, including her blood, urine, sputum culture, liver and renal function tests, which were normal.

Chest X-ray shows obliterated right cardio-phrenic angle, right entire lung field suggestive of severe right pleural effusion with passive collapse of underlying lung.
Ultrasonography guided right pleural fluid tapping was done and sent for - histopathological examination and other tests.
MRI examination and PET CT examination was performed after pleural fluid tapping. MRI of chest shows nodular enhancing thickening of entire right pleura. It is metabolically active in PET CT examination. Diaphragmatic pleura shows heterogeneously enhancing nodular mass lesion, causing that scalloping of right lobe of liver (Segment VIII) is seen in MRI and PET-CT examinations. No pericardial effusion, thickening, or calcification are seen. Enlarged and metabolically active lymph nodes are seen in internal mammary and subcarinal region. Moderate right pleural effusion and passive collapse of right lower lobe of lung are seen in MRI and PET-CT examination. Metabolically active focal osseous lesion is seen in right sacrum.

Rhabdomyosarcoma (RMS) is an malignant tumour of childhood from striated muscle origin commonly located in the head and neck region followed by extremities. Thoracic RMS is rare, and pleural RMS is extremely rare with a reported incidence of 3.8%. [1, 3] Chest wall or pleural tumours usually present with pain and swelling at local site. [3] Tumours may occasionally remain asymptomatic till they reach a large size. Pleural effusion resulting in dyspnoea may lead to earlier diagnosis. [2] Fever and weight loss is almost always present, which depends on the extent and aggressiveness of the tumour. Blood in sputum can also be seen sometimes.
CT examination is the initial imaging modality to see local extent and size of the tumour, but pleural fluid cytology may be used in the absence of detectable mass lesion. [5] Whole body PET-CT examination, MRI Thoracic imaging are key investigations for a tumour staging purpose. [3] However, histopathological examination of mass lesion is essential for definitive diagnosis. Typical imaging features of pleural RMS are abnormally enhancing solid nodular or polypoidal pleural thickening (predominantly involving coastal, diaphragmatic, and mediastinal pleura) with or without adjacent ribs involvement or extrathoracic/mediastinal invasion; variable amount of ipsilateral pleural effusion on X-Ray, U.S.G, and other cross sectional imaging; restricted diffusion within pleural thickening or mass on MRI; increased metabolic activity within it in PET-CT imaging; increased uptake in bone scan if ribs involvement; metastatic solid lesions (if present) can be seen in visceral organs; mesentery or bones evident on Whole Body CT, MRI, or PET-CT imaging modalities. Thoracic/pleural rhabdomyosarcoma has the worst prognosis due to its larger size, advanced stage at presentation, unresectability and aggressiveness. Unresectability of the lesion and presence of multiple distant bony as well as visceral organ metastases were poor prognostic factors in almost all patients. CT, MRI, and PET-CT imaging studies are most commonly used for detecting therapeutic response of tumour to chemotherapy and also to detect residual/recurrent disease. Incomplete response to chemotherapy may be combined with appropriate post-operative radiotherapy. [3, 4]

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