| Abstract|| |
Only a few cases of Ewing's sarcoma are diagnosed in adults; however, they are well described in the long bones of individuals in the 5-20 years' age group. With the following case series, we have tried to emphasize the wider age range and the involvement of short bones observed in Ewing's sarcoma patients. Fine needle aspiration has a definitive role in the early diagnosis and hence, better prognosis of this disease.
Keywords: Ewing′s sarcoma; fine needle aspiration cytology; short bones.
|How to cite this article:|
Dhingra M, Pandey R, Pantola C, Singh P K, Agarwal A. Ewing's sarcoma of short bones and girdle: A short series of five cases. J Cytol 2008;25:70-2
|How to cite this URL:|
Dhingra M, Pandey R, Pantola C, Singh P K, Agarwal A. Ewing's sarcoma of short bones and girdle: A short series of five cases. J Cytol [serial online] 2008 [cited 2020 May 29];25:70-2. Available from: http://www.jcytol.org/text.asp?2008/25/2/70/42453
| Introduction|| |
Small round cell tumors pathologically diagnosed as Ewing's sarcoma / primitive neuroectodermal tumor (ES/PNET) are well documented in the long bones of children. We report here a series of five cases of a wide age range (12–50 years) and in various short bones. All these cases were diagnosed on fine needle aspiration (FNA) and confirmed by histology and immunohistochemistry.
| Cases|| |
- A 50 year-old female patient presented with a severely painful swelling over the dorsum of her left foot that had been gradually increasing over the last eight months accompanied by intermittent fever. There was no deformity of the foot, she limped because of pain. The swelling measured 3 x 2 cm, was firm, and the overlying vessels were congested. The radiographs showed an ill-defined growth in the second metatarsal associated with a periosteal reaction.
- A 22 year-old female patient presented with a painless, progressive swelling over the left lateral region of her chest. Examination revealed a fixed swelling (1.5 cm in size) located on the ninth rib, 5 cm from the costo-chondral junction. The radiographs revealed a bony swelling with a slight periosteal elevation; there was no evidence of any soft tissue involvement.
- A 12 year-old boy developed gradual onset of pain in the right lateral hip. With a progressing limp and off-and-on high-grade fever, he underwent complete evaluation. The radiographs revealed a heterogeneous opacity 2.5 cm in size in the iliac crest, nearly 2 cm behind the iliac tubercle. A clinical diagnosis of tuberculous abscess was made.
- An 18 year-old female patient presented with a painless swelling in the back. It was localized to the medial scapular border at the level of the D6 thoracic vertebra. The radiographs showed a heterogeneous swelling at the site; it was slightly tender on deep palpation.
- A 30 year-old female patient presented with a swelling on her jaw. The radiographs showed a lytic lesion in the body of the mandible.
Aspiration in all cases was done with a 21G needle and a 10 mL syringe. Cases 1, 2, 4 and 5 yielded blood-tinged granular material, while the aspirate from Case 3 yielded about 5 mL of pus.
| Microscopic findings|| |
Fine needle aspiration from Cases 1, 2, 4, and 5 revealed almost similar cytological findings as discussed below:
Smears showed good cellularity consisting of a monomorphic population of small, round cells. The cells were almost uniform in size and shape and showed darkly staining, often irregular nuclei. The chromatin was finely granular; distinct small nuclei could be seen in most of the cells. Cytoplasm was very scanty and mitotic activity was occasionally seen. Cells were seen clustered in most places but there were areas with sparse cellularity in rosette-like formations [Figure 1]. Large cells with abundant, pale, eosinophilic, fragile cytoplasm were occasionally seen.
Case number 3 showed a different cytological picture that may be characteristic of atypical ES. Cells were slightly larger in size and showed mild pleomorphism. The nucleoli were prominent in most of these cells.
The background showed a thick, eosinophilic, necrotic material (the proteinaceous nature of this background material was evident even while spreading the smears). The necrotic component was so prominent that it dominated the smear picture. However, areas of sparse cellularity suggested some rosetting of cells. A cytological diagnosis of small round cell tumour (ES/PNET) was made.
For histological evaluation, the biopsies were processed by routine paraffin embedding and stained with hematoxylin and eosin (H & E). In addition, it showed both true and pseudorosettes that dominated the picture. There was diffuse positivity for PAS (diastase-sensitive). The diagnosis in all cases was confirmed to be ES/PNET [Figure 2].
An immunohistochemical panel consisting of desmin, NSE, CD99, and CD20 was done, of which CD99 confirmed the diagnosis [Figure 3].
| Discussion|| |
Ewing's sarcoma and PNET are primary malignant small round cell tumors of the bone and soft tissue. Current opinion is that as both Ewing's sarcoma and PNET have a similar phenotype and share identical chromosome translocation, they should be viewed as the same tumor.
James Ewing first described ES/PNET in 1921 and believed it to be a variant of diffuse endothelioma. Most patients with ES/PNET are adolescents or young adults. Although the mean age for PNET is similar to that of extraskeletal Ewing's sarcoma, there tends to be a broader age range for the former with a significant number of patients over the age of 40 years. 
ES/PNET can arise in any portion of the skeleton but usually develops in the diaphysis of the long tubular bone. Ewing's sarcoma can present a primary tumor of the jaw; most of the reported cases have been located in the maxilla. 
Arising in the medullary cavity, ES/PNET usually transgresses the cortex and periosteum, producing a soft tissue mass. The classic ES/PNET is composed of tumor cells that are twice the size of lymphocytes. The cells have indistinct cytoplasm, present as a distinct narrow rim. The nucleus has finely granular chromatin with clearly identifiable 1–3 nucleoli.
The main differential diagnoses of ES/PNET include malignant lymphoma, metastatic neuroblastoma, small cell osteogenic sarcoma, and mesenchymal chondrosarcoma. Lymphoblastic lymphoma is composed of smaller, more uniform round cells and frequently contains benign, infiltrating lymphocytes. Cells in large cell lymphomas are frequently larger than those of ES/PNET, have almost no cytoplasm, and their nuclei are irregular, cleaved, and hyperlobated.
Metastatic neuroblastoma is difficult to distinguish from ES/PNET based on only strict histological grounds. Helpful findings include the presence of neuropil and the evidence of ganglion cell differentiation. Neuroblastoma is negative for CD99; however it shows varying positivity for NSE (negative in all our cases).
If the matrix is present, ES/PNET is easily distinguishable from small cell osteosarcoma and mesenchymal chondrosarcoma. In its absence, both small cell osteosarcoma and mesenchymal chondrosarcoma contain some cells that are spindled and a vascular tree which frequently has a hemangiopericytoma-like pattern that is usually not seen in ES/PNET.
ES/PNET stains for CD99 and a negative staining should raise a possibility that the tumor may not be ES / PNET.  Although CD99 positivity has been occasionally reported in lymphomas, testing for a panel of markers helps in excluding this possibility.
Aspirates from ES are important in its definitive diagnosis. ,, All malignant round cell tumors show a similar cytological picture but the presence of monotonous, round to oval cells with hyperchromatic nuclei, finely granular chromatin, and scanty cytoplasm favors the diagnosis of ES/PNET. When compared to other malignant round cell tumors, survival rates are better for Ewing's sarcoma cases that have been diagnosed early.
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Department of Pathology, GSVM Medical College, Kanpur
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]