Alveolar rhabdomyosarcoma mimicking Burkitt lymphoma on bone marrow aspiration: case report

¹Hematology Laboratory, Mohammed VI University Hospital, Oujda, Morocco, ²Hematology Laboratory, Faculty of Medicine and Pharmacy, Mohammed First University, Oujda, Morocco, ³Pathology Laboratory, Mohammed VI University Hospital, Oujda, Morocco

^&Corresponding author
Hasnae Lekfif, Hematology Laboratory, Mohammed VI University Hospital, Oujda, Morocco

Introduction    

Rhabdomyosarcoma (RM) is the most common soft tissue neoplasm of pediatric population. Among subtypes of rhabdomyosarcoma, the alveolar subtype is classically encountered in the sinuses, breast and soft tissue of the extremities with a higher incidence in adolescents [1,2]. Bone marrow metastasis of rhabdomyosarcoma may result in diffuse infiltration with blast-like cells which makes differentiation with acute leukemia and Burkitt lymphoma a challenging task [2,3]. We report a case of metastatic rhabdomyosarcoma in a 14-years-old boy, mimicking a Burkitt lymphoma.

Patient and observation     

Patient information: a 14-years-old boy, without significant medical history.

Clinical findings: clinical examination showed a left pleural effusion syndrome with presence of numerous mobile, small cervical lymphadenopathies.

Timeline of current episode: the patient presented dyspnea and left thoracic pain. Recent weight loss and fatigue have been reported for the past 2 months period.

Diagnostic assessment: laboratory results showed leukocytes count at 11,6 x103/μl, hemoglobin at 10,5g/dl and platelet count at 482 x 103/μl. Peripheral smear showed no abnormalities. CT-scan has confirmed presence of abundant left pleural effusion with pleural thickening. Assessment of bone marrow aspiration revealed infiltration by medium to large sized monomorphic cells. These cells are either isolated or grouped together in small clusters. They have a basophilic cytoplasm and vacuoles in the cytoplasm and nucleus (Figure 1, Figure 2).

Diagnosis: morphologically, these findings were suggestive of Burkitt's lymphoma. However, a pleural biopsy was performed on the site of thickening. Pathological assessment showed infiltration by pleomorphic, atypical cells showing, on immunohistochemical study, expression of Myogenin, Myo-D1 and desmin which is consistent with an alveolar rhabdomyosarcoma (Figure 3, Figure 4).

Therapeutic intervention: the patient received chemotherapy according to the following protocol IVADa = Ifosfamide, vincristine, actinomycin, doxorubicin.

Follow-up and outcome of intervention: the patient exhibited a poor response to chemotherapy. The clinical course was marked by a deterioration in the patient's general condition, leading to death due to metastatic complications.

Informed consent: parents have expressed their consent to the publication of this report.

Discussion     

In the literature, bone marrow metastases from different neoplasms have been reported to result in intra-medullary presence of blast-like cells mimicking neoplastic cells of acute leukemia or Burkitt lymphoma. These neoplasms include: rhabdomyosarcoma as reported in our case, medullablastoma, neuroblastoma, anaplastic oligodendrioglioma, Ewing's sarcoma, small cell carcinoma and neuroendocrine tumors [4,5].

However, this phenotype is not specific for rhabdomyosarcoma neoplastic cell and can also be observed in cases of bone marrow neuroblastoma metastases which is the most common childhood tumor with such an immune-phenotype [6,7]. Many antigens exist to facilitate differentiation between RM neoplastic cells and cells from other neoplasms: gangliocyte D2 (GD2) is expressed in retinoblastoma cells (as in other neuroectodermal neoplasms) but not in cases of RM [6,8]. CD56 is found to be expressed in many tumors: blastic plasmocytoid dendritic cell neoplasias, acute myeloid leukemia, peripheral T cell lymphoma, multiple myeloma, Ewing's sarcoma, small cell carcinoma and Merkel cell carcinoma [9].

On the immunohistochemical level, RM neoplastic cells show expression of polyclonal desmine (>99% of cases), muscle-specific actin (in 95% of cases), myogenin (in 95% of cases) with a more frequent expression in the alveolar RM when compared to embryonal RM and myoglobin (in 78% of cases) [10]. Expression of myogenin is related to a poor prognosis and an aggressive behavior of the tumor [10].

Conclusion     

Rhabdomyosarcoma metastases in the bone marrow can be easily confused with hemopathies such as Burkitt lymphoma as in our case, or acute leukemia since neoplastic cells could present with blast-like morphology. Flow cytometry plays a crucial role to distinguish different entities.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

All the authors contributed to this work. They read and approved the final version of this manuscript.

Figures     

Figure 1: infiltration by medium to large sized monomorphic cells

Figure 2: neoplastic cells with basophilic cytoplasm and presence of vacuoles in the cytoplasm and nucleus

Figure 3: infiltration of pleural tissue by a small round cell proliferation (HE, 40X)

Figure 4: presence of nuclear pleomorphism among the neoplastic cells; mitotic figures were also identified (HE, 400X)

References