| Abstract|| |
Rhabdomyosarcoma (RMS) is a tumor arising from primitive mesenchymal cell with tendency for myogenesis. WHO classification categorizes this entity as embryonal, alveolar, spindle cell/sclerosing, and pleomorphic subtypes removing botryoid as a separate entity. The alveolar variant has worse prognosis and the cytological features of this entity are similar to embryonal type with little variations. This case report describes the cytohistological features of alveolar RMSfrom a 9-year-old child with nonparameningeal location.
Keywords: Alveolar, cytohistologic features, rhabdomyosarcoma
|How to cite this article:|
Sood N, Haldia AK. Nonparameningeal alveolar rhabdomyosarcoma, with cytohistological features: A case report. Indian J Pathol Microbiol 2019;62:451-3
|How to cite this URL:|
Sood N, Haldia AK. Nonparameningeal alveolar rhabdomyosarcoma, with cytohistological features: A case report. Indian J Pathol Microbiol [serial online] 2019 [cited 2020 Nov 28];62:451-3. Available from: https://www.ijpmonline.org/text.asp?2019/62/3/451/263485
| Introduction|| |
Rhabdomyosarcoma (RMS) is an aggressive/malignant tumor consisting of cells of primitive mesenchyme origin, having a profound tendency for myogenesis. It is one of the most common malignant soft tissue sarcomas in children. It accounts for approximately 4–8% of all malignancies in children less than 15 years of age. It has a bimodal presentation with one peak in children less than 6 years and a second peak around adolescence. Histologically, it has been categorized as four types: alveolar, embryonal, botryoid, and pleomorphic types. The current WHO classification, 2012, includes embryonal, alveolar, spindle cell/sclerosing, and pleomorphic subtypes of RMS and does not separate the botryoid subtype., The intergroup for rhabdomyosarcoma study however recommends its classification, based on prognosis, into superior, intermediate, and poor types. Cytological categorization of this lesion has been attempted and its categorization as alveolar and nonalveolar group has been advocated.,, Embryonal RMS (ERMS) is the commonest type seen in children.
The present case describes the cytohistological features of alveolar RMS (ARMS) in a 9-year-old child, presenting with facial swelling.
| Case Report|| |
An 8-year-old male presented with rapidly increasing swelling of right side of face for last 6 month and he was referred for fine-needle aspiration cytology. There was a history of trauma followed by nasal blockage. On examination, there was a large soft tissue mass in the right cheek with intranasal as well as palatal extension [Figure 1]. The smears were markedly cellular showing mainly dissociated round cells and focal vague alveolar pattern. Individual cells showed eccentric nuclei and scant cytoplasm with focal cytoplasmic vacuolization. Few multinucleated and binucleate cells with abundant cytoplasm were present. Focal clustering and focal phagocytosis were also noted. Hyperchromasia and high nuclear cytoplasmic(NC) ratio were observed. A cytological diagnosis of round cell tumor with ARMS likely was given [Figure 2]. The subsequent radiological examination showed an enhancing mass with lobulated outline seen involving right nasal cavity, anterior aspect of nasal septum, alveolar margin of right maxilla, and overlying subcutaneous tissue [Figure 1].
|Figure 1: (a) Clinical photograph showing swelling right side of face. (b) MRI showing enhancing mass with lobulated outline seen involving right nasal cavity, anterior aspect of nasal septum, alveolar margin of right maxilla, and overlying subcutaneous tissue|
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|Figure 2: (a) FNA smears showing alveolar pattern H and E × 400 (arrow). (b) Dissociated cells with an occasional cluster (H and E × 400). (c) Multinucleated cells with nuclei in wreath-like fashion arrow (H and E × 400). (d) Dissociated cells with focal cytoplasmic vacuoles arrow (H and E × 400). (e) Section showing alveolar pattern of neoplastic cells in subepithelial zone (H and E × 100). (f) Strong myogenin expression × 400 [diagnostic biosystems, clone F5D,0 monoclonal mice]. (g) MyoD1 expression × 400 [diagnostic biosystemsclone 5.8A, monoclonal mice]. (h) Ki-67 moderate expression × 100 [Dako, clone MIB-1, monoclonal mice]|
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Intranasal biopsy was submitted. The sections in low-power view showed tissue partially lined by stratified squamous epithelium. The underlying zone showed infiltration by tumor cells in classical alveolar pattern. Immunohistochemistry (IHC) showed intense expression of desmin, myo-D1, and myogenin. The ki-67 index was 25%. The final diagnosis of RMS alveolar type was rendered. The patient was reexamined and found to be negative for any features suggestive of neurofibromatosis or any coexisting malignancy. There was no familial history of similar lesion. He was referred for chemotherapy.
| Discussion|| |
RMS comprises a group of morphologically similar but biologically diverse lesions.ARMS was first described as a separate category in 1956 by Riopelle and Theriault. The key-defining pattern being alveolar structures was formed by the fibrous septa of these neoplasms. These septa comprised of collagenous fibrovascular tissue forming scaffolding on which were suspended and attached rhabdomyoblasts. They also enclosed central clusters of tumor cells, which appear to float in alveolar spaces. Subsequently, solid variant of ARMS was recognized, which lacks fibrous septa.WHO defined ARMS as a highly cellular, malignant neoplasm containing a monomorphous population of primitive cells with round nuclei and features of arrested myogenesis.,
ARMS most often arises in the extremities and paraspinal, paranasal, and perineal are some additional sites. According to their anatomical location and propensity for invasion of the central nervous system, the RMS is divided into orbital/parameningeal, which carry the worst prognosis and nonorbital non-parameningeal form. ARMS is less common than ERMS comprising only 20% of all pediatric RMS and rare in adults.,,
There is a rising incidence of ARMS as observed in the literature. It has been attributed to the revised criteria of The International Classification of Rhabdomyosarcoma that marks the presence of any amount of alveolar pattern in any type, diagnostic of ARMS. Child oncology group, however, has defined 50% as the defining criteria for mixed pattern. Even the microalveolar pattern in the sclerosing RMS category of WHO classification can be mistaken for ARMS.
RMS needs to be differentiated from other round cell tumor on cytology, that is, lymphomas ewing sarcoma and neuroblastoma. The clue to the diagnosis of RMS lies in identifying rhabdomyoblast, as was done in this case. Subcategorization of RMS on cytology is challenging. Klijanienkoet al. determined the diagnostic cytomorphological features of RMS on the fine-needle aspiration material. The fine-needle aspiration morphology was also correlated with histology. Alveolar subtypes were more cellular than the nonalveolar ones. Similarly, alveolar-subtype RMSs compared with nonalveolar ones exhibited more rhabdomyoblastic cells, alveolar structures, giant, multinucleated cells with nuclei in wreath like configuration, mitotic figures, and cytological atypia. Inversely, spindle-shapedcells were more frequently seen in non-ARMSs. Two major architectural patterns, mainly dissociated and mainly clustered, in presence of binucleate cells have been described. Our case showed a mix of both patterns. An addition feature noted in our case was the presence of vacuolated cells, not described so far. Atahanet al. found that the cells were more lymphocyte like in ARMS.,,
IHC plays a vital role in establishing the diagnosis. Desmin was considered a specific marker earlier but was found to be positive in other small round cell tumor. MyoD1 and myogenin are more sensitive as well as specific markers for RMS, with nuclear expression. Its staining pattern also can predict classification, as a heterogeneous pattern is more often seen inERMS, whereas strong, diffuse staining is usually noted inARMS.
Two specific recurrent translocations associated with ARMS are t(2;13) (q35–37;q14) or t(1;13)(p36;q14). Seventy percent of cases have these two alterations, with t(2;13) being much more common than t(1;13). The translocations lead to chimeric genes, which express PAX3/FKHR and PAX7/FKHR, respectively. Tumors with the t(2;13) translocation have behaved more aggressively than those with the t(1;13) translocation. This fusion gene could not be demonstrated in this case.
The prognosis depends upon the histological subtypes, site, presence of distant metastases, nonradical primary surgical procedure, tumor size >5cm, age >10 years, and time to tumor relapse. Treatment of RMS includes multidrug chemotherapy with radiotherapy and surgery.
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Conflicts of interest
There are no conflicts of interest.
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Deen Dayal Upadhaya Hospital, Government of NCT, New Delhi
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]