Alveolar soft part sarcoma: review of nine cases including twocases with unusual histology

R.JONG, R.KANDEL, V.FORNASIER, R.BELL & Y.BEDARDDepartments of Pathology and Laboratory Medicine and Orthopedic Surgery, Mount Sinai Hospital, Princess MargaretHospital and the University of Toronto, Toronto, Ontario, Canada

Date of submission 13 January 1997Accepted for publication 29 August 1997

J O N G R . , K A N D E L R . , F O R N A S I E R V. , B E L L R . & B E DA R D Y.

(1998) Histopathology 32, 63–68

Alveolar soft part sarcoma: review of nine cases including two cases with unusual histology

Aim: Alveolar soft part sarcoma is a very rare tumour.Nine cases are reviewed in order to identify new aspectsof this tumour.Methods and results: The clinical course, histological,immunohistochemical and ultrastructural features ofnine cases of alveolar soft part sarcoma were reviewed.Proliferative activity and p53 protein accumulationwere assessed immunohistochemically. The patientswere aged between 18 and 70 years. In the cases withsufficient follow-up, survival was variable with twopatients dying within 5 months and four alive at 4years. Histologically all tumours had an alveolarcomponent but one case also had a spindle component

and another case had a pseudoglandular pattern. Sixcases showed desmin immunoreactivity, one wasmuscle-specific actin positive, two were positive forS100 protein and three were positive for vimentin.MIB-1 immunostaining was seen in up to 35% of cells.Two cases showed p53 protein accumulation.Conclusions: There appeared to be no correlationbetween short term survival (4 years or less) andclinical presentation, adjuvant treatment, tumour size,histological grade, vascular invasion by tumour, pro-liferative index, or p53 protein accumulation. Althoughunusual, spindle cell or pseudoglandular componentscan be seen in alveolar soft part sarcoma.

Keywords: alveolar soft part sarcoma, proliferation, p53

Introduction

Alveolar soft part sarcoma (ASPS) is a rare tumour thatcomprises approximately 0.5% to 1.0% of all soft tissuesarcomas1. In this report, the clinical presentation andcourse, light and electron microscopic features, andimmunohistochemical profile of these tumours arereviewed and the results compared to those in theliterature. We also examined these tumours for poten-tial prognostic factors for short-term survival includingproliferative activity as determined by MIB-1 immuno-staining, and p53 protein accumulation as determinedimmunohistochemically.

Materials and methods

In the files of the Pathology Department of Mount Sinai

Hospital and Princess Margaret Hospital, nine cases ofalveolar soft part sarcoma were identified. The clinicalhistory and course of the patients were reviewed as wellas the histological features of the formalin-fixed,paraffin-embedded haematoxylin and eosin (H & E)stained tissue.

Representative sections were selected for periodicacid–Schiff (PAS/D) staining followed by diastase diges-tion and immunohistochemical staining. For immuno-histochemical staining, the sections were mounted onaminopropyltriethoxysilane coated slides. The sectionswere incubated with antibodies reactive to vimentin,myoglobin (Biogenex, San Ramon, CA), desmin, S100protein (Dako Corp., Santa Barbara, CA), muscle-specific actin (Biomeda Corp., Foster City, CA), MIB-1(AMAC, Westbrook, ME) and p53 (Novocastra, New-castle-Upon-Tyne, UK). In all cases, immunoreactivitywas detected using a biotinylated secondary antibody,and biotin–avidin–peroxidase complex detection

Histopathology 1998, 32, 63–68

q 1998 Blackwell Science Limited.

Address for correspondence: Dr Y.Bedard, Department of Pathologyand Laboratory Medicine, Mount Sinai Hospital, 600 UniversityAvenue, Toronto, Ontario M5G 1X5, Canada.

system (Vectastain, Vector, Burlingame, CA, for p53 andMIB-1 antibodies or Autoprobe III reagent set, BiomedaCorp., Foster City, CA, for all other antibodies). In allcases, known positive controls were used and thenegative controls consisted of leaving out primaryantibody.

Tissue from seven of the nine tumours was submittedfor ultrastructural examination following fixation in 2%

glutaraldehyde for 24 h, and post-fixation in 1%osmium tetroxide. Sorensen’s buffer was used in bothsolutions. Thin sections were sequentially stained withuranyl acetate and lead citrate and examined with atransmission electron microscope.

The tumours were classified into three grades basedon a modification of a grading system describedpreviously2. Briefly, the grade is determined by assessing

64 R.Jong et al.

q 1998 Blackwell Science Ltd, Histopathology, 32, 63–68.

Table 1. Clinical features and treatment

Age/sex* Maximum sizeCase (Years) Site (mm) Adjuvant treatment

1 38/M Arm 59 Chemotherapy2 70/F Back 50 None3 54/M Thigh 60 None4 45/M Presented with lymph node – Chemotherapy

metastases, primary unknown5 18/F Thigh 55 Chemotherapy and radiotherapy6 43/M Presented with lung metastases, 85 Lung nodules resected

primary in thigh7 21/F Arm 25 Chemotherapy and radiotherapy8 24/F Thigh 82 Chemotherapy9 46/F Presented with lung metastases, – Chemotherapy

primary unknown

* M, male, F, female.

Table 2. Histological and immunohistochemical features and clinical course

Histological Vascular space MIB-1*Case appearance of tumour Grade invasion (%) p53 Clinical course

1 Alveolar pattern III þ 18 þ Lung/brain metsDied 4 years

2 Alveolar and pseudoglandular pattern III – 13 – RecurrenceDied 3 years

3 Alveolar pattern II þ 4 – ANEDAlive 4 years

4 Alveolar and spindle pattern II þ 13 þ Died 4 months5 Alveolar pattern II – 3 – Lung mets

Alive 3 years6 Alveolar pattern III – 35 – Presented with lung

mets 1986, ANEDAlive 11 years

7 Alveolar pattern II – 0.3 – Lung/brain metsDied 6 years

8 Alveolar pattern II – 1 – Lung and brain metsAlive 4 years

9 Alveolar pattern II – 6 – Died 5 months

* Percentage of cells immunopositive/total cells × 100. –, negative; þ, positive; and ANED, alive with no evidence of disease.

tumour cellularity ($50% cells to matrix), nuclearpleomorphism (presence or absence), mitotic counts($6 mitoses/10 HPF, ×400 magnification) and thepresence of tumour cell necrosis ($15% of thetumour). Tumours having one of these above featureswere considered grade I; tumours with two featureswere considered grade II; and those with three or moreof these features were considered grade III.

The MIB-1 labelling index was calculated in all casesusing an ocular grid and counting 300 cells in randomfields at ×400 magnification. If 300 cells were notpresent, then all tumour cells were counted. Thepercentage MIB-1 positive cells was calculated by thenumber of positive MIB-1 stained nuclei divided by thetotal number of tumour nuclei counted. Three hundredcells were counted in seven out of nine cases. Because ofthe small area of tumour in the other two cases, only150 and 50 tumour cell nuclei were evaluated,respectively. For p53, all nuclear staining, regardless ofthe intensity, was considered positive.

Results

As summarized in Table 1, the patients ranged from 15to 70 years of age with a mean of 39 years; five werefemale and four were male. Three tumours presented inthe thigh, two in the arm, and one in the back. Threecases presented initially as distant metastases (two inthe lungs and one in lymph nodes), for which a primarysite was identified in one case. In this case, the patientpresented with lung metastases 8 years before thediagnosis of the primary tumour, which was in thethigh. In addition to surgical excision of the tumours,six patients had adjuvant chemotherapy. Of these sixpatients, two patients also had adjuvant radiotherapy.Two patients were dead with metastatic disease within 5months and four are alive at least 4 years after diagnosis(Table 2). Two patients are alive with no evidence ofdisease after 4 years.

Light microscopic examination showed that alltumours had the classic alveolar pattern with cellsexhibiting eosinophilic or clear cytoplasm (Figure 1a).There was a variable degree of nuclear pleomorphismand necrosis which were reflected in the tumour grade.One case also had a prominent pseudoglandularappearance (Figure 1b), whereas another case had aspindle cell or sarcomatoid morphology (Figure 1c). Inboth of these cases, the tumours had areas whichexhibited the classical alveolar features. Vascularinvasion was noted in three of the cases. PAS/D stainingrevealed cytoplasmic inclusions, which were granularand/or crystalline in configuration. Inclusions wereseen in the spindle cell component as well.

All seven tumours submitted for ultrastructural

examination showed characteristic intracytoplasmicmembrane-bound crystalline rhomboid-shaped gran-ules which had an average periodicity of 10 nm (Figure2). These were in close approximation to Golgiapparatus. In some cases, spherical to ovoid secretory

Alveolar soft part sarcoma 65

q 1998 Blackwell Science Ltd, Histopathology, 32, 63–68.

Figure 1. a, Case 8 showing characteristic alveolar pattern (H & E,magnification ×100). b, Case 2 showing pseudoglandulardifferentiation (H & E, magnification ×400). c, Case 4 showingspindle cell differentiation (H & E, magnification ×250).

granules were also found. No true glandular luminalined by microvilli or desmosomes were identified.

Desmin was positive in six out of nine cases, muscle-specific actin was positive in one and myoglobin wasnegative in all nine cases. Reactivity for vimentin wasdetected in three tumours and for S100 protein in two.

MIB-1 labelling index ranged from 0.3% to 35% oftumour cell nuclei. The three tumours that were gradeIII had the highest MIB-1 positivity ranging from 13.3%to 35% (Figure 3). p53 immunoreactivity was detectedin two cases. For case 6, MIB-1 labelling index and p53protein accumulation were assessed in both the primarytumour and the lung metastasis, and no difference wasdetected between the two lesions. As summarized inTable 2, there was no correlation between the clinicalcourse and pathological features including proliferativerate, as measured by Ki67 (MIB-1) reactivity and p53protein accumulation.

Discussion

ASPS was first described by Christopherson et al. in

1952 and presents most commonly as a soft tissuetumour3. Our clinical data are consistent with thatreported in the literature4–9. Although our studyshowed a wide variation in age of presentation, mostpatients were in their second to fourth decades. Therewas a slight female predominance. The tumoursoccurred most frequently in the thigh (four cases) andarm (two cases). Three cases presented as metastaseswhich is in keeping with the literature. The overallsurvival of ASPS is considered poor, with an estimated10 year survival of 38%, mainly due to early metastaticdisease1. In our series the follow-up is not sufficient todetermine 10 year survival rates, but there was a widevariability in survival, with death occurring in twopatients within 5 months of presentation while twopatients are alive without evidence of metastatic diseaseat 4 and 11 years after presentation.

The classic alveolar morphology was present in allour cases. It has been suggested in the literature thatthis alveolar pattern is produced by central necrosis ofsolid islands of tumour cells, leaving tumour cells liningthin fibrovascular septa7. To our knowledge, there have

66 R.Jong et al.

q 1998 Blackwell Science Ltd, Histopathology, 32, 63–68.

Figure 2. Electron micrograph showing intracytoplasmic crystalline inclusions (magnification ×85 000).

been no previous reports describing a spindle cellcomponent in ASPS as was seen in one of our cases.The spindle component was associated with the usualalveolar component and crystal inclusions were seen bylight microscopy following PAS/D staining as well asultrastructurally. Another case had a glandular compo-nent which likely represents pseudoglandular formationas no microvilli or desmosomes were seen by electronmicroscopy.

Numerous studies have been undertaken to ascertainthe histogenesis of this tumour10–17. To date, it has notbeen identified and remains controversial. Some studieshave suggested derivation from skeletal muscle basedprimarily on the presence of desmin immunoreactivityin tumour cells. However, desmin immunoreactivity canoccur in non-myogenic tumours and cannot be used asdefinitive evidence of skeletal muscle differentiation1. Inour series, desmin was positive in six out of nine cases,whereas muscle-specific actin was positive in only onecase and no cases showed myoglobin immunoreactivity.These results are consistent with those found in theliterature. Myo D1, is a nuclear phosphoproteinpostulated to be involved in the regulation of the early

differentiation of non-committed mesenchymal cells toa myogenic lineage18. Myo D1 immunoreactivity hasbeen detected in some cases of ASPS19,20, but a recentreport showed this immunoreactivity was cytoplasmicand not nuclear, indicating that this was a non-specificfinding21. Cytoplasmic staining was also observed in allour cases (data not shown).

There was no correlation between the behaviour ofthe tumours (short-term vs. long-term survival) and theclinical and pathological parameters including tumoursize, histological pattern, tumour grade, vascular spaceinvasion, presentation with metastatic disease at thetime of diagnosis, or use of adjuvant chemotherapy and/or radiotherapy. Although this may be due to the smallsize of this study. All our cases were either grade II or IIItumours similar to what has been reported in theliterature but, as suggested by Enzinger and Weiss, thistumour can behave more aggressively than indicated bythe degree of cytological atypia and mitotic activity1.Several studies have shown that proliferative index andp53 protein overexpression may be useful prognosticfactors in soft tissue sarcomas22–26, although this maynot be valid for all types of soft tissue sarcomas. For

Alveolar soft part sarcoma 67

q 1998 Blackwell Science Ltd, Histopathology, 32, 63–68.

Figure 3. MIB-1 immunostaining of case 6 showing 35% nuclear immunoreactivity (immunoperoxidase, magnification ×640).

example, in malignant fibrous histiocytoma no statisti-cally significant correlation could be demonstratedbetween Ki67 and prognosis27. Similarly, no correlationwas seen between p53 protein accumulation andprognosis in primary leiomyosarcoma of bone28. Pro-liferative index and p53 protein accumulation asdetermined immunohistochemically were used in anattempt to predict clinical behaviour. Neither of thesetwo parameters identified those who would die earlyafter presentation.

This review demonstrates that in addition to theclassical alveolar pattern, other components such asspindle cells and pseudogland formation can occur inASPS. In this series, four out of the eight patients (onepatient has had only 3 year follow-up) died within 4years after presentation and we were not able to identifyany clinical or pathological indicators to predict whichpatients might follow a more clinically aggressivecourse.

Acknowledgements

We thank Jackie Pittman for technical assistance andPaula Esposito for secretarial assistance.

References1. Enzinger FM, Weiss SW. Alveolar soft part sarcoma. Soft Tissue

Tumors, 3rd ed. St. Louis: CV Mosby, 1995; 13, and 1067–1074.2. Costa J, Wesley RA, Glatstein A, Rosenberg SA. The grading of soft

tissue tumors: results of a clinical histopathologic correlation in aseries of 163 cases. Cancer 1984; 53; 530–541.

3. Christopherson WM, Foote FW Jr, Stewart FW. Alveolar soft partsarcomas: structurally characteristic tumors of uncertainhistogenesis. Cancer 1952; 5; 100–111.

4. Evans HL. Alveolar soft-part sarcoma. A study of 13 typicalexamples and one with a histologically atypical component.Cancer 1985; 55; 912–917.

5. Auerbach HE, Brooks JJ. Alveolar soft part sarcoma: Aclinicopathologic and immunohistochemical study. Cancer1987; 60; 66–73.

6. Persson S, Willems JS, Kindblom LG, Angervall L. Alveolar softpart sarcoma. An immunohistochemical, cytologic and electron-microscopic study and a quantitative DNA analysis. Virch. Archiv.A. Pathol. Anat. Histopathol. 1988; 412; 499–513.

7. Lieberman PH, Brennan MF, Kimmel M, Erlandson RA, Garin-Chesa P, Flehinger BY. Alveolar soft part sarcoma: A clinico-pathologic study of half a century. Cancer 1989; 63; 1–13.

8. Matsuno Y, Mukai K, Itabashi M et al. Alveolar soft part sarcoma.A clinicopathologic and immunohistochemical study of 12 cases.Acta. Pathol. Jpn 1990; 40; 199–205.

9. Nakashima Y, Kotoura Y, Kasakura K et al. Alveolar soft-partsarcoma: A report of ten cases. Clin. Orthop. Rel. Res. 1993; 294;259–266.

10. DeSchryver-Kecskemeti K, Kraus FT, Engleman W, Lacy PE.

Alveolar soft-part sarcoma-a malignant angioreninoma. Histo-chemical, immunocytochemical, and electron microscopic studyof four cases. Am. J. Surg. Pathol. 1982; 6; 5–18.

11. Mukai M, Torikata C, Iri H et al. Histogenesis of alveolar soft partsarcoma. An immunohistochemical and biochemical study. Am. J.Surg. Pathol. 1986; 10; 212–218.

12. Foschini M, Ceccarelli C, Eusebi V et al. Alveolar soft part sarcoma:immunological evidence of rhabdomyoblastic differentiation.Histopathology 1988; 13; 101–108.

13. Mukai M, Torikata C, Shimoda T, Iri H. Alveolar soft partsarcoma. Assessment of immunohistochemical demonstration ofdesmin using paraffin sections and frozen sections. Virch. Archiv.A. Pathol. Anat. 1989; 414; 503–509.

14. Ordonez NG, Ro JY, Mackay B. Alveolar soft part sarcoma. Anultrastructural and immunocytochemical investigation of itshistogenesis. Cancer 1989; 63; 1721–1736.

15. Miettinen M, Ekfors T. Alveolar soft part sarcoma. Immuno-histochemical evidence of muscle cell differentiation. Am. J. Clin.Pathol. 1990; 93; 32–38.

16. Menesce LP, Eyden BP, Edmonson D, Harris M. Immunophenotypeand ultrastructure of alveolar soft part sarcoma. J. Submicrosc.Cytol. Pathol. 1993; 25; 377–387.

17. Foschini M, Eusebi V. Alveolar soft part sarcoma: A new type ofrhabdomyosarcoma? Sem. Diag. Pathol. 1994; 11; 58–68.

18. Weintraub H, Davis R, Tapscott S et al. The myo D gene family:nodal point during specification of the muscle cell lineage. Science1991; 251; 761–766.

19. Rosai J, Dias P, Parham D et al. Myo D1 protein expression inalveolar soft part sarcoma as confirmatory evidence of its skeletalmuscle nature. Am. J. Pathol. 1990; 15; 974–981.

20. Tallini G, Parham DM, Dias P, Cordon-Cardo C, Houghton PJ,Rosai J. Myogenic regulatory protein expression in adult softtissue sarcomas: A sensitive and specific marker of skeletal muscledifferentiation. Am. J. Pathol. 1994; 144; 693–701.

21. Wang NP, Bacchi CE, Jiang JJ, McNutt MA, Gown AM. Doesalveolar soft-part sarcoma exhibit skeletal muscle differentiation?An immunocytochemical and biochemical study of myogenicregulatory protein expression. Mod. Pathol. 1996; 9; 496–506.

22. Ueda T, Aozasa K, Tsujimoto M et al. Prognostic significance of Ki-67 reactivity in soft tissue sarcomas. Cancer 1989; 63; 1607–1611.

23. Kroese MCS, Rutgens DH, Wils IS, Van Unnik JAM, Roholl PJM.The relevance of the DNA index and proliferation rate in gradingof benign and malignant soft tissue tumors. Cancer 1990; 65;1782–1788.

24. Kawai A, Noguchi M, Beppu Y et al. Nuclear immunoreaction ofp53 protein in soft tissue sarcomas. Cancer 1994; 73; 2499–2505.

25. Oda Y, Hashimoto H, Takeshita S, Tsuneyoshi M. The prognosticvalue of immunohistochemical staining for proliferating cellnuclear antigen in synovial sarcoma. Cancer 1993; 72; 478–485.

26. Drobnjak M, Latres E, Pollack D et al. Prognostic implications ofp53 nuclear overexpression and high proliferation index of Ki-67in adult soft-tissue sarcomas. J. Natl. Cancer Inst. 1994; 86; 549–554.

27. Zehr RJ, Bauer TW, Marks KE, Weltevreden A. Ki-67 and gradingof malignant fibrous histiocytomas. Cancer 1990; 66; 1984–1990.

28. Khoddami M, Bedard YC, Bell RS, Kandel RA. Primaryleiomyosarcoma of bone: report of five cases and review of theliterature. Arch. Pathol. Lab. Med. 1996; 120; 671–675.

68 R.Jong et al.

q 1998 Blackwell Science Ltd, Histopathology, 32, 63–68.