Case Report
Imaging Findings and Histologic Appearances of Alveolar Soft Part Sarcoma in the Prostate: A Case Report and Review of the Literature Jingya Chen,1 Xiao Chen,1 Yaohui Wang,2 Hu Chen,1 Zhongqiu Wang1 Clinical Practice Points ASPS is a rare malignant soft tissue tumor that most
commonly occurs in young patients, with a slight predominance in women. It can occur in any region of the body but is typically seen in the extremities. We report the first case of ASPS arising from the prostate in a 21-year-old man who presented
with difficulty in urination, abdominal pain, and fever. A reliable diagnosis of ASPS can be made according to the clinical features, imaging findings, and histologic appearances.
Clinical Genitourinary Cancer, Vol. 13, No. 4, e315-9 ª 2015 Elsevier Inc. All rights reserved. Keywords: Alveolar soft part sarcoma, CT, Histology, Imaging, MRI, Prostate
Introduction Alveolar soft part sarcoma (ASPS) is a rare type of malignant soft tissue tumor that mostly occurs in the lower extremities of adolescent girls or young women. Primary ASPS usually acts as a slowgrowing irregular soft mass with an ill- or well-defined boundary. Early metastases are frequently observed in the lungs and brain, which lead to an unfavorable outcome.1 The tumor is defined histologically by the presence of cells arranged in nests or a pseudoalveolar pattern and large, eosinophilic tumor cells.2 The origin of ASPS is still unclear.3 Unusual locations, such as breast, bone, and kidney, have been reported.4-6 However, to our knowledge, no ASPS occurring in the prostate has been reported in the literature. ASPS typically appears to be hypervascular on contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI).3 Heterogeneous density and signal on CT and MRI indicate the different components of the mass, such as hemorrhage, fibrosis, necrosis, and cyst. Surgical resection is recommended for the treatment of primary ASPS. Complementary chemotherapy also is needed considering the common reoccurrence and distant 1
Department of Radiology, Affiliated Hospital Chinese Medicine, Nanjing, Jiangsu Province, Department of Pathology, Affiliated Hospital Chinese Medicine, Nanjing, Jiangsu Province, 2
of Nanjing University of Traditional China of Nanjing University of Traditional China
Submitted: Nov 14, 2014; Revised: Dec 17, 2014; Accepted: Dec 26, 2014; Epub: Dec 31, 2014 Address for correspondence: Zhongqiu Wang, MD, Department of Radiology, Affiliated Hospital of Nanjing University of Traditional Chinese Medicine, 155 Hanzhong Road, Nanjing 210029, Jiangsu Province, China E-mail contact: [email protected]
1558-7673/$ - see frontmatter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clgc.2014.12.016
metastasis.7 No specific clinical symptoms can be found in patients with ASPS. Therefore, the imaging and histologic findings must be assessed carefully for early diagnosis. In this report, we present the imaging findings and clinical and histologic features of ASPS occurring in the prostate in a 21-year-old man and give a brief review of the literature.
Case Report Clinical Data A 21-year-old man presented to the Affiliated Hospital of Nanjing University of Traditional Chinese Medicine with difficulty in urination, abdominal pain, and fever. Pollakiurie, dysuria, poor urinary stream, and abdominal pain had been present for 2 months. The patient recently had a fever. He was admitted to our hospital for diagnosis and treatment. Hypertension, headaches, palpitations, and a history of urinary cancer were not present in the patient. An enlarged prostate gland, which was hard and tender, was observed during digital rectal examination. The rest of the physical examination results were unremarkable. Routine urine test results showed that the number of erythrocytes was 227/mL and C-reactive protein was 167 mg/L. The cancer antigen 125 was 209.15 U/mL. The prostate-specific antigen level was within normal range.
Computed Tomography and Magnetic Resonance Imaging Findings A large, multilobulated, partially ill-defined, and heterogeneous mass with centric low density and fine calcification was observed in the presacral space on unenhanced CT images (Figure 1A). The tumor was 8.4 7.4 6.5 cm. After intravenous contrast
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Alveolar Soft Part Sarcoma in the Prostate medium injection, the peripheral regions of the lesion were enhanced during the arterial (Figure 1B), venous (Figure 1C), and delay (Figure 1D) phases. The time-intensity curve is shown in Figure 2F. The enhancement reached the peak at the venous phase (80 seconds after contrast agent injection) and then slowly declined. A small amount of fluid in the right pleural space (Figure 1E) was found during CT scan of the chest and abdomen. MRI showed more detailed information on the mass. On T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI), the signal intensity of the peripheral solid part was slightly higher than that of the adjacent muscle and lower than that of fat. Multiple little cystic low signals on T1WI (Figure 2A) and high signals on T2WI (Figure 2B) also were observed. A higher signal was found in the solid part on diffusion-weighted imaging (DWI) (Figure 2C). The centric parts of the mass were shown as a heterogeneous low signal on T1WI,
T2WI, and DWI. In addition, scar-like higher T1 and T2 signals were observed, and the signals were not decreased on fat-suppressed T2WI (Figure 2A, B, D). Sagittal fat-suppressed T2WI showed the mass arising from the prostate and infiltrating to the trigon of bladder (Figure 2E). Intratumoral signal voids were observed on T2WI and coronal fat-suppressed T2WI (Figure 2F), which indicated that the blood flow was high in the tumors. According to the imaging findings, the lesion should be differentiated with prostate sarcoma or paraganglioma.
Surgery and Histopathologic Evaluation The patient underwent an ultrasound-guided transrectal prostate biopsy. Adenocarcinoma was considered in the biopsy report. Radical bladder cystectomy and urinary diversion were performed. Further histologic examination showed the tumor was
Figure 1 CT Imaging Findings of the ASPS. A, Conventional CT Scan Reveals a Multilobulated Soft Tissue Mass in the Prostate With Low Density in the Center (asterisk) and Fine Calcification (arrow). Contrast-Enhanced CT Scan Shows a Gradually and Heterogeneously Enhanced Lesion in the Peripheral Region in the Arterial Phase (B), Venous Phase (C), and Delay Phase (D), but No Obvious Enhancement Is Found in the Center (asterisk). E, CT Scan Also Shows That Pleural Effusion (arrow) Is Found in the Right Side of the Chest. F, the Time-Intensity Curve Shows the Characteristics of Post-Contrast Enhancement
Abbreviation: CT ¼ computed tomography.
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Jingya Chen et al Figure 2 MRI Findings of the ASPS. A Slightly Higher Signal than That of the Muscle Is Observed on T1WI (A) and T2WI (B). The Centric Part Shows a Heterogeneous Low Signal (asterisk). High Signals Also are Found in the Solid Tissues and Part of the Centric Area on DWI (C), Which Suggests That the Centric Area Is Composed of Cystic Tissues and Some Solid Tissues. The ScarLike Higher Signals on T1 and T2 (triangle) Do Not Decrease on Fat-Suppressed T2WI (D). Sagittal Fat-Suppressed T2WI (E) Shows the Mass Arising From the Prostate and Infiltrated to the Trigon of Urinary Bladder (arrow). Intratumoral Signal Voids (curved arrow) on Coronal Fat-Suppressed T2WI (F) Suggest That There are High Blood Flows
predominantly composed of cells arranged in nests, and there was a lack of cellular cohesion within the nests. The cells had distinct borders and abundant eosinophilic cytoplasm, resulting in an epithelioid appearance. The nests of cells were separated by extracellular vascular and fibrous matrix. Fibrosis structure (Figure 3A, B) was found in the central part of the tumor. The nuclei of the cells were large and vesicular, but the nucleoli were small. Immunohistochemical examination showed that the tumor was positive for transcription factor E3 (Figure 3B), myogenic differentiation 1 (Figure 3D), and neuron-specific enolase, but was negative for S100, epithelial membrane antigen, synaptophysin, inhibin-A, and chromogranin A. The final diagnosis of ASPS was made on the basis of the imaging findings and histopathologic results. During the 3-month follow-up, the pleural effusion in the right chest was totally absorbed and no evidence of recurrence was found.
Discussion ASPS is a rare malignant soft tissue neoplasm, which accounts for 0.5% to 1% of all soft tissue sarcomas.8 It usually occurs in young people aged 15 to 35 years and slightly more often in women.7 Approximately 60% of cases occur in the deep soft tissue of the extremities.9 ASPS in rare locations, such as the breast, bone, and kidney, have been reported.1-3 In this study, we report a rare case of ASPS occurring in the prostate. CT and MRI revealed a large lobulated mass in the prostate with peripheral enhancement. The peripheral solid part of the lesion showed a slightly high signal on T1WI and T2WI and a high signal on DWI. The centric part of the lesion was present as a low signal on T1WI, T2WI, and DWI. Pain does not usually occur in patients with ASPS. Because of the relative lack of clinical symptoms, the tumor is easily overlooked and usually presents as large (mean diameter, 9 cm; range, 2-15 cm). Distant metastasis may be the first disease manifestation.7 The
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Alveolar Soft Part Sarcoma in the Prostate Figure 3 Histopathologic (A, 340; B, 3100) and Immunochemical (C, 3100; D, 3200) Appearances of ASPS. The Peripheral Part of the Tumor Is Identified As Tumor Tissue (A, asterisk), and the Central Part Is Proved to be Fibrous Structure (A, triangle). An Alveolar Pattern of the Lesion Is Observed (B). Positive Expression of Transcription Factor E3 (C) and Myogenic Differentiation 1 (D) are Observed in Tumor Tissues
tumor reported is a large mass (7.4 6.5 8.4 cm), but the dysuria caused by the tumor is a valuable clue for further examination. Our patient had abdominal pain, which may have been caused by the tumor infiltration of bladder, although it is still unknown whether the pleural effusion was metastasis or an inflammatory reaction. The fluid was absorbed 3 months later, which made the latter view reliable. The prognosis of localized ASPS is good after en bloc surgical resection. The 5-year survival rate could reach 81% to 85%.4 No evidence of local recurrence or distant metastasis was found in this patient during 3 months of follow-up. ASPS is a type of neoplasm that is rich in blood vessels.6 Imaging findings clearly reflect this feature. CT scan demonstrates avid and delayed enhancement of the solid part of the mass, whereas the fibrosis, necrosis, and cystoids areas are unenhanced. The tumor commonly shows a high signal on T1WI and T2WI and multiple intratumoral signal voids. The high signal on T1WI is due to the slow-flowing blood supply in the tumor.10 High T2 signal is seen in most malignant masses because of the interstitial fluid, and it is not the specific finding. Multiple signal voids within the lesion can be attributed to vascular proliferation, which has been frequently observed in ASPS.11 It is partly or totally well circumscribed on MRI, which demonstrates that the mass was surrounded by fibrous pseudocapsule. Peripheral enhancement on CT scan demonstrated that the mass was a hypervascular tumor. The peripheral part of the lesion showed a high signal on T1WI and T2WI, which also suggested that the peripheral part of the lesion was solid pathologic
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tissue with abundant slow blood supply. The hypervascular imaging feature is nonspecific because prostate sarcomas, such as rhabdomyosarcoma and leiomyosarcoma, are also hypervascular tumors. However, most other subtypes of sarcomas appear as a low- or isointense mass on T1WI and a hyperintense mass on T2WI,12 which is different from the typical MRI signals of ASPS. An irregular patchy area in the center with a low signal represents fibrous component. The little scar-like areas with an intermediate to high signal are believed to be the mucus but not hemorrhage because those areas are low density on CT. Most important, serpentine signal voids are found in the lesion, which represent high-flow vascular channels. When multiple signal voids are observed in the setting of a lesion with a high signal on T1WI and T2WI, ASPS should be considered.13 Imaging findings have an important accessory diagnostic value for ASPS. Furthermore, they are useful for the detection of local adenopathy and distant metastases. ASPS is histologically defined by the presence of pseudoalveolar pattern and eosinophilic large tumor cells.5 It is named by the typical structure pattern but not the tissue origin. There is a debate about the histogenesis of ASPS. Different views, including the histogenesis of myogenic cell, Schwann cell, or paraganglial cell, have been reported.14 These different views are given depending on the variants of pathologic and immunohistochemical characteristics. ASPS may resemble many neoplastic conditions, such as renal cell carcinoma and paragangliomas.15 In most case reports, paraganglioma shows strong synaptophysin and chromogranin A expression. Epithelial membrane antigen is a useful biomarker for
Jingya Chen et al the definitive diagnosis of renal cell carcinoma and its metastases. However, these proteins are usually negative in ASPS.14 Transcription enhancer factor 3 can express in ASPS or granular cell tumors, but S-100 protein and inhibin are negative in ASPS but positive in granular cell tumor.16 These features were present in our case. Nonspecific markers, such as neuron-specific enolase and vimentin, may be positive in approximately 30% to 50% of ASPS.5 By combining the information, the diagnosis of APS is confirmed. Radical resection of primary and metastatic lesions is recommended to be the mainstay of treatment for ASPS.3 Although there is no definitive evidence that chemotherapy and radiation therapy improve patient survival, they are needed to prevent local relapse and distant metastasis.7
Conclusions
We showed the imaging findings and histologic appearance of ASPS in the prostate in a young man. To our knowledge, this is the first case of ASPS in the prostate. On review of the literature, a diagnosis of ASPS should be considered when a hypervascular mass arises from soft tissue with a high signal on T1WI and T2WI. The clinical features, imaging findings, and histologic appearance should be considered together to confirm the diagnosis.
Disclosure The authors have stated that they have no conflicts of interest.
References 1. Zadnik PL, Yurter A, DeLeon R, et al. Alveolar soft-part sarcoma in the sacrum: a case report and review of the literature. Skeletal Radiol 2014; 43:115-20. 2. Folpe AL, Deyrup AT. Alveolar soft-part sarcoma: a review and update. J Clin Pathol 2006; 59:1127-32. 3. Itani M, Shabb NS, Haidar R, et al. AIRP best cases in radiologic-pathologic correlation: alveolar soft-part sarcoma. Radiographics 2013; 33:585-93. 4. Wu J, Brinker DA, Haas M, et al. Primary alveolar soft part sarcoma (ASPS) of the breast: report of a deceptive case with xanthomatous features confirmed by TFE3 immunohistochemistry and electron microscopy. Int J Surg Pathol 2005; 13:81-5. 5. Zhu FP, Lu GM, Zhang LJ, et al. Primary alveolar soft part sarcoma of vertebra: a case report and literature review. Skeletal Radiol 2009; 38:825-9. 6. Kim JM, Im SA, Oh SN, et al. Alveolar soft part sarcoma arising from the kidney: imaging and clinical features. Korean J Radiol 2014; 15:381-5. 7. Pennacchioli E, Fiore M, Collini P, et al. Alveolar soft part sarcoma: clinical presentation, treatment, and outcome in a series of 33 patients at a single institution. Ann Surg Oncol 2010; 17:3229-33. 8. Christopherson WM, Foote FW Jr, Stewart FW. Alveolar soft-part sarcomas; structurally characteristic tumors of uncertain histogenesis. Cancer 1952; 5:100-11. 9. Portera CA Jr, Ho V, Patel SR, et al. Alveolar soft part sarcoma: clinical course and patterns of metastasis in 70 patients treated at a single institution. Cancer 2001; 91: 585-91. 10. Dong A, Wang Y, Cheng C, et al. CT, MRI, and FDG PET/CT in a patient with alveolar soft part sarcoma. Clin Nucl Med 2014; 39:265-7. 11. Chen YD, Hsieh MS, Yao MS, et al. MRI of alveolar soft-part sarcoma. Comput Med Imaging Graph 2006; 30:479-82. 12. Andreou A, Whitten C, MacVicar D, et al. Imaging appearance of sarcomas of the prostate. Cancer Imaging 2013; 13:228-37. 13. Suh JS, Cho J, Lee SH, et al. Alveolar soft part sarcoma: MR and angiographic findings. Skeletal Radiol 2000; 29:680-9. 14. Ju HU, Seo KW, Jegal Y, et al. A case of alveolar soft part sarcoma of the pleura. J Korean Med Sci 2013; 28:331-5. 15. Mannan R, Bhasin TS, Kaur P, et al. Prominent intracytoplasmic crystals in alveolar soft part sarcoma (ASPS): an aid in cytological diagnosis. J Clin Diagn Res 2014; 8:145-6. 16. Chamberlain BK, McClain CM, Gonzalez RS, et al. Alveolar soft part sarcoma and granular cell tumor: an immunohistochemical comparison study. Hum Pathol 2014; 45:1039-44.
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Imaging Findings and Histologic Appearances of Alveolar Soft Part Sarcoma in the Prostate: A Case Report and Review of the Literature Jingya Chen,1 Xiao Chen,1 Yaohui Wang,2 Hu Chen,1 Zhongqiu Wang1 Clinical Practice Points ASPS is a rare malignant soft tissue tumor that most
commonly occurs in young patients, with a slight predominance in women. It can occur in any region of the body but is typically seen in the extremities. We report the first case of ASPS arising from the prostate in a 21-year-old man who presented
with difficulty in urination, abdominal pain, and fever. A reliable diagnosis of ASPS can be made according to the clinical features, imaging findings, and histologic appearances.
Clinical Genitourinary Cancer, Vol. 13, No. 4, e315-9 ª 2015 Elsevier Inc. All rights reserved. Keywords: Alveolar soft part sarcoma, CT, Histology, Imaging, MRI, Prostate
Introduction Alveolar soft part sarcoma (ASPS) is a rare type of malignant soft tissue tumor that mostly occurs in the lower extremities of adolescent girls or young women. Primary ASPS usually acts as a slowgrowing irregular soft mass with an ill- or well-defined boundary. Early metastases are frequently observed in the lungs and brain, which lead to an unfavorable outcome.1 The tumor is defined histologically by the presence of cells arranged in nests or a pseudoalveolar pattern and large, eosinophilic tumor cells.2 The origin of ASPS is still unclear.3 Unusual locations, such as breast, bone, and kidney, have been reported.4-6 However, to our knowledge, no ASPS occurring in the prostate has been reported in the literature. ASPS typically appears to be hypervascular on contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI).3 Heterogeneous density and signal on CT and MRI indicate the different components of the mass, such as hemorrhage, fibrosis, necrosis, and cyst. Surgical resection is recommended for the treatment of primary ASPS. Complementary chemotherapy also is needed considering the common reoccurrence and distant 1
Department of Radiology, Affiliated Hospital Chinese Medicine, Nanjing, Jiangsu Province, Department of Pathology, Affiliated Hospital Chinese Medicine, Nanjing, Jiangsu Province, 2
of Nanjing University of Traditional China of Nanjing University of Traditional China
Submitted: Nov 14, 2014; Revised: Dec 17, 2014; Accepted: Dec 26, 2014; Epub: Dec 31, 2014 Address for correspondence: Zhongqiu Wang, MD, Department of Radiology, Affiliated Hospital of Nanjing University of Traditional Chinese Medicine, 155 Hanzhong Road, Nanjing 210029, Jiangsu Province, China E-mail contact: [email protected]
1558-7673/$ - see frontmatter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clgc.2014.12.016
metastasis.7 No specific clinical symptoms can be found in patients with ASPS. Therefore, the imaging and histologic findings must be assessed carefully for early diagnosis. In this report, we present the imaging findings and clinical and histologic features of ASPS occurring in the prostate in a 21-year-old man and give a brief review of the literature.
Case Report Clinical Data A 21-year-old man presented to the Affiliated Hospital of Nanjing University of Traditional Chinese Medicine with difficulty in urination, abdominal pain, and fever. Pollakiurie, dysuria, poor urinary stream, and abdominal pain had been present for 2 months. The patient recently had a fever. He was admitted to our hospital for diagnosis and treatment. Hypertension, headaches, palpitations, and a history of urinary cancer were not present in the patient. An enlarged prostate gland, which was hard and tender, was observed during digital rectal examination. The rest of the physical examination results were unremarkable. Routine urine test results showed that the number of erythrocytes was 227/mL and C-reactive protein was 167 mg/L. The cancer antigen 125 was 209.15 U/mL. The prostate-specific antigen level was within normal range.
Computed Tomography and Magnetic Resonance Imaging Findings A large, multilobulated, partially ill-defined, and heterogeneous mass with centric low density and fine calcification was observed in the presacral space on unenhanced CT images (Figure 1A). The tumor was 8.4 7.4 6.5 cm. After intravenous contrast
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Alveolar Soft Part Sarcoma in the Prostate medium injection, the peripheral regions of the lesion were enhanced during the arterial (Figure 1B), venous (Figure 1C), and delay (Figure 1D) phases. The time-intensity curve is shown in Figure 2F. The enhancement reached the peak at the venous phase (80 seconds after contrast agent injection) and then slowly declined. A small amount of fluid in the right pleural space (Figure 1E) was found during CT scan of the chest and abdomen. MRI showed more detailed information on the mass. On T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI), the signal intensity of the peripheral solid part was slightly higher than that of the adjacent muscle and lower than that of fat. Multiple little cystic low signals on T1WI (Figure 2A) and high signals on T2WI (Figure 2B) also were observed. A higher signal was found in the solid part on diffusion-weighted imaging (DWI) (Figure 2C). The centric parts of the mass were shown as a heterogeneous low signal on T1WI,
T2WI, and DWI. In addition, scar-like higher T1 and T2 signals were observed, and the signals were not decreased on fat-suppressed T2WI (Figure 2A, B, D). Sagittal fat-suppressed T2WI showed the mass arising from the prostate and infiltrating to the trigon of bladder (Figure 2E). Intratumoral signal voids were observed on T2WI and coronal fat-suppressed T2WI (Figure 2F), which indicated that the blood flow was high in the tumors. According to the imaging findings, the lesion should be differentiated with prostate sarcoma or paraganglioma.
Surgery and Histopathologic Evaluation The patient underwent an ultrasound-guided transrectal prostate biopsy. Adenocarcinoma was considered in the biopsy report. Radical bladder cystectomy and urinary diversion were performed. Further histologic examination showed the tumor was
Figure 1 CT Imaging Findings of the ASPS. A, Conventional CT Scan Reveals a Multilobulated Soft Tissue Mass in the Prostate With Low Density in the Center (asterisk) and Fine Calcification (arrow). Contrast-Enhanced CT Scan Shows a Gradually and Heterogeneously Enhanced Lesion in the Peripheral Region in the Arterial Phase (B), Venous Phase (C), and Delay Phase (D), but No Obvious Enhancement Is Found in the Center (asterisk). E, CT Scan Also Shows That Pleural Effusion (arrow) Is Found in the Right Side of the Chest. F, the Time-Intensity Curve Shows the Characteristics of Post-Contrast Enhancement
Abbreviation: CT ¼ computed tomography.
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Jingya Chen et al Figure 2 MRI Findings of the ASPS. A Slightly Higher Signal than That of the Muscle Is Observed on T1WI (A) and T2WI (B). The Centric Part Shows a Heterogeneous Low Signal (asterisk). High Signals Also are Found in the Solid Tissues and Part of the Centric Area on DWI (C), Which Suggests That the Centric Area Is Composed of Cystic Tissues and Some Solid Tissues. The ScarLike Higher Signals on T1 and T2 (triangle) Do Not Decrease on Fat-Suppressed T2WI (D). Sagittal Fat-Suppressed T2WI (E) Shows the Mass Arising From the Prostate and Infiltrated to the Trigon of Urinary Bladder (arrow). Intratumoral Signal Voids (curved arrow) on Coronal Fat-Suppressed T2WI (F) Suggest That There are High Blood Flows
predominantly composed of cells arranged in nests, and there was a lack of cellular cohesion within the nests. The cells had distinct borders and abundant eosinophilic cytoplasm, resulting in an epithelioid appearance. The nests of cells were separated by extracellular vascular and fibrous matrix. Fibrosis structure (Figure 3A, B) was found in the central part of the tumor. The nuclei of the cells were large and vesicular, but the nucleoli were small. Immunohistochemical examination showed that the tumor was positive for transcription factor E3 (Figure 3B), myogenic differentiation 1 (Figure 3D), and neuron-specific enolase, but was negative for S100, epithelial membrane antigen, synaptophysin, inhibin-A, and chromogranin A. The final diagnosis of ASPS was made on the basis of the imaging findings and histopathologic results. During the 3-month follow-up, the pleural effusion in the right chest was totally absorbed and no evidence of recurrence was found.
Discussion ASPS is a rare malignant soft tissue neoplasm, which accounts for 0.5% to 1% of all soft tissue sarcomas.8 It usually occurs in young people aged 15 to 35 years and slightly more often in women.7 Approximately 60% of cases occur in the deep soft tissue of the extremities.9 ASPS in rare locations, such as the breast, bone, and kidney, have been reported.1-3 In this study, we report a rare case of ASPS occurring in the prostate. CT and MRI revealed a large lobulated mass in the prostate with peripheral enhancement. The peripheral solid part of the lesion showed a slightly high signal on T1WI and T2WI and a high signal on DWI. The centric part of the lesion was present as a low signal on T1WI, T2WI, and DWI. Pain does not usually occur in patients with ASPS. Because of the relative lack of clinical symptoms, the tumor is easily overlooked and usually presents as large (mean diameter, 9 cm; range, 2-15 cm). Distant metastasis may be the first disease manifestation.7 The
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Alveolar Soft Part Sarcoma in the Prostate Figure 3 Histopathologic (A, 340; B, 3100) and Immunochemical (C, 3100; D, 3200) Appearances of ASPS. The Peripheral Part of the Tumor Is Identified As Tumor Tissue (A, asterisk), and the Central Part Is Proved to be Fibrous Structure (A, triangle). An Alveolar Pattern of the Lesion Is Observed (B). Positive Expression of Transcription Factor E3 (C) and Myogenic Differentiation 1 (D) are Observed in Tumor Tissues
tumor reported is a large mass (7.4 6.5 8.4 cm), but the dysuria caused by the tumor is a valuable clue for further examination. Our patient had abdominal pain, which may have been caused by the tumor infiltration of bladder, although it is still unknown whether the pleural effusion was metastasis or an inflammatory reaction. The fluid was absorbed 3 months later, which made the latter view reliable. The prognosis of localized ASPS is good after en bloc surgical resection. The 5-year survival rate could reach 81% to 85%.4 No evidence of local recurrence or distant metastasis was found in this patient during 3 months of follow-up. ASPS is a type of neoplasm that is rich in blood vessels.6 Imaging findings clearly reflect this feature. CT scan demonstrates avid and delayed enhancement of the solid part of the mass, whereas the fibrosis, necrosis, and cystoids areas are unenhanced. The tumor commonly shows a high signal on T1WI and T2WI and multiple intratumoral signal voids. The high signal on T1WI is due to the slow-flowing blood supply in the tumor.10 High T2 signal is seen in most malignant masses because of the interstitial fluid, and it is not the specific finding. Multiple signal voids within the lesion can be attributed to vascular proliferation, which has been frequently observed in ASPS.11 It is partly or totally well circumscribed on MRI, which demonstrates that the mass was surrounded by fibrous pseudocapsule. Peripheral enhancement on CT scan demonstrated that the mass was a hypervascular tumor. The peripheral part of the lesion showed a high signal on T1WI and T2WI, which also suggested that the peripheral part of the lesion was solid pathologic
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tissue with abundant slow blood supply. The hypervascular imaging feature is nonspecific because prostate sarcomas, such as rhabdomyosarcoma and leiomyosarcoma, are also hypervascular tumors. However, most other subtypes of sarcomas appear as a low- or isointense mass on T1WI and a hyperintense mass on T2WI,12 which is different from the typical MRI signals of ASPS. An irregular patchy area in the center with a low signal represents fibrous component. The little scar-like areas with an intermediate to high signal are believed to be the mucus but not hemorrhage because those areas are low density on CT. Most important, serpentine signal voids are found in the lesion, which represent high-flow vascular channels. When multiple signal voids are observed in the setting of a lesion with a high signal on T1WI and T2WI, ASPS should be considered.13 Imaging findings have an important accessory diagnostic value for ASPS. Furthermore, they are useful for the detection of local adenopathy and distant metastases. ASPS is histologically defined by the presence of pseudoalveolar pattern and eosinophilic large tumor cells.5 It is named by the typical structure pattern but not the tissue origin. There is a debate about the histogenesis of ASPS. Different views, including the histogenesis of myogenic cell, Schwann cell, or paraganglial cell, have been reported.14 These different views are given depending on the variants of pathologic and immunohistochemical characteristics. ASPS may resemble many neoplastic conditions, such as renal cell carcinoma and paragangliomas.15 In most case reports, paraganglioma shows strong synaptophysin and chromogranin A expression. Epithelial membrane antigen is a useful biomarker for
Jingya Chen et al the definitive diagnosis of renal cell carcinoma and its metastases. However, these proteins are usually negative in ASPS.14 Transcription enhancer factor 3 can express in ASPS or granular cell tumors, but S-100 protein and inhibin are negative in ASPS but positive in granular cell tumor.16 These features were present in our case. Nonspecific markers, such as neuron-specific enolase and vimentin, may be positive in approximately 30% to 50% of ASPS.5 By combining the information, the diagnosis of APS is confirmed. Radical resection of primary and metastatic lesions is recommended to be the mainstay of treatment for ASPS.3 Although there is no definitive evidence that chemotherapy and radiation therapy improve patient survival, they are needed to prevent local relapse and distant metastasis.7
Conclusions
We showed the imaging findings and histologic appearance of ASPS in the prostate in a young man. To our knowledge, this is the first case of ASPS in the prostate. On review of the literature, a diagnosis of ASPS should be considered when a hypervascular mass arises from soft tissue with a high signal on T1WI and T2WI. The clinical features, imaging findings, and histologic appearance should be considered together to confirm the diagnosis.
Disclosure The authors have stated that they have no conflicts of interest.
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Clinical Genitourinary Cancer August 2015
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