Rare site and age of presentation: Prostatic sarcoma of the Ewing family in an adolescent

INTRODUCTION

Ewing sarcoma/primitive neuroectodermal tumors (PNETs) are the second-most primary malignant bone tumor in children and adolescents, but the extraosseous sarcomas rarely manifest in the prostate.^[1] The worldwide reported number of prostate Ewing’s sarcoma is <10. These have a very poor survival rate of less than a year due to rapid growth and recurrence with a survival rate of 10% only. It imposes an increased risk of chronic health conditions which not only adds to the financial burden but also impairs the functioning of life.^[2] The case discussed was a minor with prostate sarcoma.

CASE REPORT

A 14-year-old patient, an Afghanistan immigrant, was referred from another city to the emergency department with 3 months history of right flank pain, burning micturition, and poor stream. The patient’s past medical history was unremarkable.

On initial assessment and suspicion of a pelvic mass, the ultrasound pelvis revealed a large heterogeneously hyperechoic lesion with central necrosis and increased blood flow on Doppler ultrasound.

The MRI pelvis with and without contrast on Axial T1WI [Figure 1], T2WI, SAGITAL and T2WI coronal, and diffusion-weighted image (DWI) axial images showed large abnormal signal intensity mass, measuring 7.3 × 6.4 × 6.7 cm, isointense to the muscles on T1WI and T2WI with significant post-contrast enhancement and central area of necrosis seen. The mass was encasing the right-sided iliac vessels and ureter. Posteriorly, it was infiltrating the seminal vesicles and prostate gland [Figure 2]. The fat planes were also focally indistinct with the rectum. The DWI [Figure 3] showed high signal intensity in the large prostatic tumor due to restricted diffusion, while the apparent diffusion coefficient (ADC) map derived from DWI images showed a low ADC value in the prostate tumor.

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Figure 1:

A sagittal T1WI and T2W2 MRI image of the prostate: The prostate is almost entirely replaced by the tumor mass. The mass is indenting the bladder base. The central necrotic area is noted (white arrow).

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Figure 2:

A pre- and post-contrast axial T1WI MRI pelvis image shows enhanced prostate mass with the central area of necrosis (white arrow).

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Figure 3:

Diffusion-weighted image shows high signal intensity in large prostatic mass due to restricted diffusion (white arrow).

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Transrectal ultrasound-guided biopsy under general anesthesia was done to establish the histological evaluation and complete tumor staging of the mass. It showed characteristic cores of neoplastic lesions exhibiting sheets of distinguished small round blue cells with scanty cytoplasm and monomorphic hypochromatic nuclei. The panel of IHC markers showed leukocyte common antigen, chromogranin, and myogenin negative, whereas CD99 showed diffuse membranous positivity and Fli-1 diffuse nuclear positivity [Figure 4]. Both morphological and IHC features were characteristic of Ewing’s sarcoma/PNET.

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Figure 4:

Histopathology of the lesion. (a) Low-power view showing two cores of lesion composed entirely of tumor tissue (HE, ×50). (b). High-power view showing small round blue cell tumor (blue arrow) (HE, ×400). (c) CD 99 immunostaining showing diffuse membranous positivity in tumor cells (blue arrow) (CD, ×400). (d). FLI 1 immunostaining showing diffuse nuclear positivity in tumor cells (blue arrow) (FLI 1, ×400).

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The contrast computerized tomography (CT scan) of the chest, abdomen, and pelvis showed heterogeneous enhancing locally infiltrating lesions in the pelvis [Figure 5]. The perilesional, inguinal, and para-aortic lymphadenopathy was suggestive of PNET, while the CT chest appeared normal. The bone marrow biopsy of the iliac crest and bone scintigraphy was negative for metastatic involvement of the skeleton. The prostate-specific antigen was 0.10 ng/ml. Initially, blood urea and creatinine were normally raised and fluctuated from 6.7 to 1.2 mg/dl, but bilateral percutaneous nephrostomy intervention addressed the concern effectively. The treatment strategy for Ewing’s family of carcinoma including PNET is multimodal. This includes chemotherapy followed by surgery and radiotherapy. Chemotherapy often is a combination therapy.

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Figure 5:

An axial section of CT scan pelvis on portovenous phase shows mild enhanced prostatic mass. A single area of necrosis is noted in the mass (white arrow).

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DISCUSSION

In 1921, James Ewing described the fourth most frequent primary malignant tumor of bone accounting for approximately 3% of all pediatric cancers.^[1,3] Ewing sarcoma is most frequent in the first three decades of life.^[3] The extraskeletal Ewing sarcoma is rare having a prevalence of 15%. Moreover, Ewing sarcoma of bone is 20%.^[3] It usually manifests in young patients.^[2,4]

The various reported sites of extraskeletal Ewing sarcoma include the paravertebral region (32%), lower extremities (26%), chest wall (18%), retroperitoneum (11%), pelvis and hip (11%), and upper extremities (3%).^[2,4] The genitourinary system and other visceral organs are exceptionally rare sites of occurrence. Other rare reported sites are the urinary bladder, kidneys, adrenal gland, and penis.^[5,6] Until now, the literature review revealed that the worldwide reported number of prostate Ewing’s sarcoma is < 10 including our case. Almost all the patients were young adults (median age 27, range: 20–31). This reflects it’s very rare, exhibits poor survival, and occurrence.^[4-6]

The diagnostic confusion occurred regarding the extraskeletal manifestation of Ewing’s sarcoma, but the case fulfilled the diagnostic criteria of extraosseous Ewing’s sarcoma by having the following characteristics:

(a) MRI showed no osseous involvement, (b) bone scintigraphy revealed no increased uptake of bone or periosteum adjacent to the tumor in static images, (c) light microscopy manifested lesions consisting of small round blue cells with no differentiation features, and (d) exhibited cytoplasmic glycogen.^[7]

The poor prognosis of pelvic disease owes to large masses imposing difficulty in full resection.^[4,8] Lung metastasis is the most common (80%). The MRI proved to be vital to evaluate response to neoadjuvant therapy (chemotherapy, radiotherapy, or both) and to detect local recurrence or metastatic disease.^[9] Almost 1–2% of survivors are at risk of developing a secondary malignancy along with 20% of second bone sarcoma.^[10]

Multidisciplinary management is the mainstay of treatment initiated by a biopsy to confirm the diagnosis, followed by neoadjuvant chemotherapy (before local control) and adjuvant (after local control) therapy. The size of the primary tumor shall be reduced by surgical resection, radiation therapy (RT), or both. This provides not only local control but also evaluates the degree of tumor necrosis and aids in preventing the recurrence emerging from small islands of chemotherapy-resistant cells.^[10] The combination therapeutic approach with aggressive therapies such as surgery and chemotherapy (with or without RT) shall improve 5-year survival.

The case under discussion is about the prostate. Once multi-agent chemotherapy is completed and tumor size reduced by surgical resection, the patient would need prostatectomy which will be followed by radiotherapy to improve survival duration.

The strength of this case report is the availability of the data from the management team. The patient is under treatment for the final cycle of chemotherapy. Following chemotherapy, the size of the tumor regression shall be assessed and monitored for radical prostatectomy. Being an inhabitant of a distant city the future compliance and adherence to treatment are uncertain. In developing countries, the impact of socioeconomic barriers and poor health services is detrimental factors and may impede future compliance.

CONCLUSION

Sarcomas are a rare, but clinically relevant differential diagnosis in a young adult presenting with a large heterogeneous mass in the trunk, extremities, or soft tissues with internal hemorrhage and cystic necrosis, along with the lack of calcification and nodal metastases, which may help to establish the diagnosis and manage accordingly.

The rare occurrence of Ewing’s sarcoma of prostate and poor prognosis garners enough attention to the differential diagnosis, histological confirmation, and definitive classification to establish multimodal, interdisciplinary, and collaborative treatment approaches for optimal and cost-effective therapeutic measures.