INTRATHORACIC RHABDOMYOSARCOMA



INTRATHORACIC RHABDOMYOSARCOMA

Ramachandran PV, Della Harigovind

Akbar Sherif VS, Remesh Babu Mottammel, Feroz M

MEDICAL COLLEGE, CALICUT, KERALA, INDIA

Abstract:

Intrathoracic rhabdomyosarcoma is a rare entity, though rhabdomyo-sarcoma is a common childhood soft tissue neoplasm. A case of botryoid embryonal rhabdomyosarcoma in intrathoracic location is reported here, first suspected from ultrasonography due to the characteristic morphology, corroborated by computed tomography and confirmed by histology.

Key words: Intrathoracic, Botryoid embryonal rhabdomyosarcoma,

Ultrasonography, Computed tomography

Short title : Intrathoracic Rhabdomyosarcoma

INTRODUCTION

Rhabdomyosarcoma (RMS), a primary mesenchymal tumour with rhabdo- myoblastic differentiation, is the most common soft tissue malignancy in childhood. RMS can arise in any site, even when striated muscle is not normally present, presumably from the pleuripotent cells capable of differentiating into neurogenic and myogenic elements. Common primary sites of RMS are the head and neck, the genitourinary tract and the extremities. Other less common primary sites include the trunk, intrathoracic region, the gastrointestinal tract and the perineal / anal region. Intrathoracic Rhabdomyosarcomas are extremely rare with very few number of reported cases in literature. Thoracic RMS usually present late and becomes quite large by the time of diagnosis.

CASE REPORT

An 11 year old girl was admitted to Paediatrics Department of our hospital with complaints of breathlessness and cough. Her symptoms were of short duration and prior to that she was totally asymptomatic. There was no sputum, wheezing or fever. As a part of routine investigation chest radiography was done and it showed complete opacity of the left hemithorax with mediastinal shift to right side (Fig.1). Blood investigations were all within normal limits. Assuming the opacity to be due to large pleural effusion, USG thorax was requested to confirm the presence of fluid. Thoracic sonography showed large anechoic fluid collection in left thoracic cavity with multiple echogenic nodules projecting into it from the periphery, abundant at lung base (Fig.2,3). Discrete as well as confluent nature of the echogenic nodules was the first due to a rare neoplastic disease, as chest X-ray could not have detected them separate from the fluid density. Computed Tomography (CT) study of thorax was resorted to in an attempt to further characterize the echogenic nodules. Plain and contrast enhanced helical CT scan of thorax (Fig.4,5) revealed the presence of a large cystic mass lesion with numerous varying sized soft tissue density mural nodules along the periphery of the cyst projecting inwardly. Entire left hemithorax was filled with the mass compressing and causing total collapse of the left lung and producing marked mediastinal shift to the right. The individual nodules were contiguous in lower zone, indicating involvement of diaphragmatic pleura. There was no mediastinal lymphadenopathy. No chest wall involvement was noted. At this stage a rare intrathoracic neoplasm was postulated and the child was posted for exploration in an attempt to obtain histopathology of the lesion, as FNAC was repeated inconclusive, yielding only fluid with scanty abnormal cells. Since the lesion was considered to be inoperable, an open biopsy was performed and the histopathological examination of the specimen was reported as embryonal rhabdomyosarcoma. At present child is on combination chemotherapy, aiming for a remission.

HISTORY

Embryonal Rhabdomyosarcoma, the most common of the three histological types of RMS, is commonly seen in paediatric age group. Histologically it is a small round cell tumour having uniform round cells with hyperchromatic nuclei (Fig.6). The differentiation from other small round cell tumours of childhood is aided by the presence of rhabdomyoblasts which have abundant eosinophilic cytoplasm and eccentric nucleus. Embryonal rhabdomyosarcomas when protrude into serous cavities or urinary bladder results in a subtype called botryoid embryonal Rhabdomyosarcoma, which on histology shows the cambium layer as shown in this case (Fig.7). An important differential diagnosis to be considered, both clinically and histologically is pleuropulmonary blastoma which also can show a cambium layer (Dehner LP et al, 1994; Perdikogianni C et al, 2001). Immunohistochemistry helps to differentiate between the two.

DISCUSSION

Paediatric soft tissue sarcomas are a group of malignant tumours that originate from primitive mesenchymal tissue and account for 8% of all childhood tumours. RMS, a tumour of skeletal muscle origin, account for more than half of all cases of soft tissue sarcomas in children. It constitutes 3.5% of the cases of cancer among children aged 0-14 years, and 2% of cases among adolescents and young adults, 15-19 years of age. Three histological types are described. Embryonal, alveolar and pleomorphic, of which most common is embryonal type and mostly affects head and neck regions in the first decade of life. Alveolar type arising intramuscularly is common in adolescents. Pleomorphic type affecting extremity muscles is rare in children. Sarcoma botryoides, a form of embryonal Rhabdomyosarcoma, typically affecting bladder, vagina, prostate and urethra, presents as a polypoid submucosal mass.

The site of primary tumour is an important determinant of prognosis. Those arising in orbit, genitourinary tract, prostate and paratesticular areas have the best prognosis. The unfavourable sites include extremities, retroperitoneum, intra- thoracic locations, head and neck, perineum, ear and sinus (Saenz NC et al, 1997). Among the histological subtypes, alveolar RMS is usually more aggressive because it is associated with adverse prognostic sites more than the other types. Intrathoracic rhabdomyosarcomas are unusual, with only few cases reported in literature (Kumar AP et al, 1977; McDermott VG et al, 1993; Eustace S et al, 1993; Gupta AK et al, 1999; Almberger M et al, 2001). Though complete remissions and attempted stem cell rescue have been reported in literature, cerebral and skeletal metastases also are known to occur (Micallef-Eynaud Pd et al, 1993; Almberger et a, 2001). Imaging is necessary for the diagnosis and staging of these tumours. Chest X-ray may not contribute much in the diagnosis but may be the initial indicator of the disease. Opacity of hemithorax is the usual finding which has a poor specificity. Ultrasonography plays a crucial role in the diagnosis. The presence of soft tissue nodules along the periphery of the cystic mass that protrude into the fluid filled cavity from lung, pleura and diaphragm can suggest the possibility of a neoplastic process. CT and MRI are highly effective in further characterization of the soft tissue nodules. While mediastinal involvement is well demonstrated with CT (Marasco WJ et al, 1991), MRI has been proved to be more helpful in defining local infiltration of chest wall and providing accurate information on the extent of diaphragmatic involvement (Stark P et al, 1994; Almberger M et al, 2001).

REFERENCES

1. Almberger M, Lannicelli E, Matrunola M, Sachiavetti A, Capocassia P. Integrated diagnostic imaging of primary thoracic rhabdomyosarcoma. European Radiology 2001; 11: 506-8.

2. Dehner LP, Lauren V, Ackerman. Pleuropulmonary blastoma is the pulmonary plastoma of childhood. Semin Diagn Pathol 1994 May; 11(2): 144-51.

3. Gladish GW, Sabloff BM, Munden RF, Truong MT, Erasmus JJ, Chasen MH. Primary thoracic sarcomas, Radiographics 2002 May-June; 22 (3): 621-37.

4. Gupta AK, Mitra DK, Berry M. Primary embryonal rhabdomyosarcoma of the diaphragm in a child : case report. Paediatr Radiol 1999; 29: 823-5.

5. Kumar AP, Green A, Smith JW, Pratt CB. Combined therapy for malignant tumours of chest wall in children. J Paediatr Surg. 1977; 12: 991-9.

6. Marasco WJ, Hruban RH, Fishman EK. Mediastinal involvement by alveolar rhabdomyosarcoma: evaluation with computerized tomography. South Med J 1991 Jul; 84(7): 924-6.

7. McDermott VG, Mackenzie S, Hendry GM. Primary Intrathoracic Rhabdomyosarcoma – A rare childhood malignancy : Case Report. Br J Radiol 1993 Oct.66 (790): 937-41.

8. Micallef-Eynaud PD, Goulden NT, Langdale-Brown B, Eden TB, Steers JW. Intra- cerebral recurrence of primary intrathoracic Rhabdomyosarcoma. Med. Pediatr. Oncol. 1993; 21(2): 132-6.

9. Perdikogianni C, Stiakaki E, Danilatou V, Delides G, Kalmanti M. Pleuropulmonary blastoma : an aggressive intrathoracic neoplasm of childhood. Pediatr Hematol Oncol 2001 Jun; 18(4): 259-66.

10. Saenz NC, Ghavini F, Gerald W, Gollamundi S, La Qualgia MP. Chest wall Rhabdomyosarcoma. Am Cancer Society 1997; 80: 1513-7.

11. Stark P, Eber CD, Jacobson F. Primary intrathoracic malignant mesenchymal tumours : pictorial essay. J Thorac Imaging. 1994 Summer; 9(3): 48-55.

Figure Legends:

Fig.1 : CXR-Opacity (Lt) hemithorax

Fig.2 (Lt) & Fig.3(Rt): - USS – Fluid collection in left pleural cavity with

echogenic nodules projecting into it.

Fig.4 (Lt) & Fig.5(Rt): CT Thorax – Cystic mass lesion with mural nodules

along periphery

Fig.6 : Microscopy showing uniform, small round cells with hyperchromatic

nuclei arranged in sheets (H&E x 200)

Fig.7 : Microscopy showing cambium layer with rhabdomyoblasts,

shown by the two arrow (H&E x 200)

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