Journal of Cytology
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Year : 2022  |  Volume : 39  |  Issue : 4  |  Page : 190-192
Alveolar rhabdomyosarcoma with CD 56 positivity: A mimic of extranodal NK/T cell lymphoma

Department of Pathology, Janakpuri Superspeciality Hospital, Delhi, India

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Date of Submission14-Oct-2021
Date of Decision03-May-2022
Date of Acceptance10-Oct-2022
Date of Web Publication29-Oct-2022

How to cite this article:
Kumar U, Das A, Sahu R, Kachhap P. Alveolar rhabdomyosarcoma with CD 56 positivity: A mimic of extranodal NK/T cell lymphoma. J Cytol 2022;39:190-2

How to cite this URL:
Kumar U, Das A, Sahu R, Kachhap P. Alveolar rhabdomyosarcoma with CD 56 positivity: A mimic of extranodal NK/T cell lymphoma. J Cytol [serial online] 2022 [cited 2023 Mar 27];39:190-2. Available from:

Dear Sir,

Alveolar rhabdomyosarcoma (ARMS) is a distinct subtype of rhabdomyosarcoma. It usually arises in extremities and axial musculature.[1] These lesions affect all ages and are more common in adolescents and young adults, unlike other subtypes which are more common in childhood.[1],[2] Head and neck are uncommon sites of ARMS.[1] Alveolar rhabdomyosarcoma is extremely difficult to distinguish from other primitive round cell neoplasms without immunohistochemistry and/or genetic study. Expression of CD 56 is seen in 30–40% of ARMS.[2] We represent an unusual case of alveolar rhabdomyosarcoma with CD56 positivity which was diagnosed outside as extranodal NK/T cell lymphoma on flow-cytometry. CD56 is expressed in hematolymphoid and nonhematolymphoid neoplasm. Hematolymphoid neoplasm includes NK/T cell lymphoma, Myeloid sarcoma, Pediatric anaplastic large cell lymphoma, plasmacytoid dendritic cell neoplasm, gamma delta (γδ) T cells, and activated CD8+ T cells as well as on dendritic cells (DCs). Other nonhematolymphoid neoplasms include alveolar rhabdomyosarcoma, meningioma, pulmonary meningothelial-like nodules, Merkel cell carcinoma, Neuroblastoma (adult), neuroendocrine carcinomas, pancreatic neuroendocrine tumor, pheochromocytoma, synovial sarcoma, and Wilms tumor. However, we could establish an accurate diagnosis on careful observation of cytomorphological features and immunohistochemistry on cell blocks.

A 25-year-old female presented with a nasal mass with recent-onset exertional dyspnea and occasional epistaxis. She was diagnosed outside with extranodal NK/T cell lymphoma on flow-cytometry and was referred to our hospital for further treatment. On CECT PNS there was a soft tissue mass in the left anterior nasal cavity inseparable from the left-sided nasal turbinates, septum, and hard palate. CT guided fine needle aspiration cytology was done, as the material was too scant only cell blocks were made. H and E sections showed moderate cellularity and sheets of dyscohesive cells. These cells were small round cells having irregular hyperchromatic nuclei, inconspicuous nucleoli, and scant to moderate eosinophilic cytoplasm. Few mitotic figures were also seen. On immunohistochemistry these cells were positive for desmin, myogenin, myo D1, and CD 56. The cells were negative for LCA and cytokeratin. A diagnosis of alveolar rhabdomyosarcoma was rendered.

Cytologically alveolar rhabdomyosarcoma shows singly dispersed small blue round cells with occasional eccentric nuclei and abundant eosinophilic cytoplasm. Differential diagnosis includes malignant lymphoma, Ewings sarcoma, neuroblastoma, retinoblastoma, nephroblastoma, synovial sarcoma, and poorly differentiated carcinoma. However, it is difficult to make a definite diagnosis on cytological findings alone.[2],[3] On-site evaluation of these tumors on FNAC is difficult due to their resemblance to hematological malignancies. As a result, the aspirate undergoes immunophenotyping to exclude non-Hodgkin lymphoma (NHL). The strong positivity of CD 56 on immunophenotyping can lead to an erroneous diagnosis, as seen in our case. However, pathologists should be alerted by CD 45 negativity.

There are some differentiating cytomorphological features of NK/T cell lymphoma which differentiate alveolar rhabdomyosarcoma. The Cytomorphological feature of NK/T cell lymphoma is the hypercellular pattern with dyscohesive sheets of the polymorphous infiltration of the small, medium, and large atypical lymphocytes interspersed with plasma cells, macrophages, neutrophils, and occasional histiocytes. Cells show scant to moderate amounts of cytoplasm with pleomorphic nuclei and small nucleoli. These atypical cells are positive for CD 56 and CD 45 on cell block sections, while FNAC of rhabdomyosarcoma revealed dyscohesive sheets of small blue round cells with occasional eccentric nuclei and abundant eosinophilic cytoplasm [Figure 1]a,[Figure 1]b. Few cells are arranged in an alveolar pattern. Immunohistochemically, the tumor cells expressed CD56 but CD 45 negative [Figure 2]a, [Figure 2]b, [Figure 2]c, [Figure 2]d, [Figure 2]e, [Figure 2]f. Pathologists should be alerted by CD 45 negativity.
Cellblock of fine-needle aspiration from nasal mass shows the polymorphous population of tumor cells with eccentrically placed hyperchromatic nuclei with abundant eosinophilic cytoplasm. Mitosis also seen. (H and E; Magnification (a) x100 & (b) x 400)

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[a-f] Immunocytochemistry; (a) CD56 showing membranous positivity; (b) desmin showing cytoplasmic positivity in large neoplastic cells; (c) myogenin showing diffuse and strong nuclear positivity; (d-e) Ki67 and myoD1 showing nuclear positivity; (f) CD 45 showing negative staining

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Win KT et al.[4] reported a similar case of ARMS where the initial diagnosis of Extranodal NK/T cell lymphoma was made on flow-cytometry. Yasuda T et al.[5] also concluded in their study that establishing the diagnosis of ARMS in older adults is usually neglected due to its rarity in this age group, lack of a characteristic alveolar pattern, and CD 56 positivity.

To conclude, CD 56 positive cells should be cautiously studied, we should employ a panel of markers, including desmin, myogenin/MyoD1, and genetic study in the diagnosis of small round cell tumors so that the possibility of this condition is not overlooked.

Key message

We should employ a panel of markers including desmin and myogenin/MyoD1 in the diagnosis of small round cell tumors so that the possibility of this condition is not overlooked.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Chen E, Ricciotti R, Futran N, Oda D. Head and neck rhabdomyosarcoma: Clinical and pathologic characterization of seven cases. Head Neck Pathol 2017;11:321-6.  Back to cited text no. 1
Bahrami A, Gown AM, Baird GS, Hicks MJ, Folpe AL. Aberrant expression of epithelial and neuroendocrine markers in alveolar rhabdomyosarcoma: A potentially serious diagnostic pitfall. Mod Pathol 2008;21:795-806.  Back to cited text no. 2
Rajwanshi A, Srinivas R, Upasana G. Malignant small round cell tumors. J Cytol 2009;26:1-10.  Back to cited text no. 3
[PUBMED]  [Full text]  
Win KT, Lee MY, Tan TD, Tsai M, Tsai MP, Bahrami A, et al. Nasopharyngeal alveolar rhabdomyosarcoma expressing CD56: A mimicker of extranodal natural killer/T-cell lymphoma. Int J Clin Exp Pathol 2014;7:451-5.  Back to cited text no. 4
Yasuda T, Perry KD, Nelson M, Bui MM, Nasir A, Goldschmidt R, et al. Alveolar rhabdomyosarcoma of the head and neck region in older adults: Genetic characterization and a review of the literature. Hum Pathol 2009;40:341-8.  Back to cited text no. 5

Correspondence Address:
Dr. Rani Sahu
C2A, Janakpuri Superspecialist Hospital, Delhi - 110 058
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/joc.joc_211_21

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