Objective: Immunophenotypic characterization of high grade (pleomorphic) sarcomas and determination of their frequency, mean/median age, sex preferences and common sites in Pakistani patients.

Methods: This study included 134 consecutive cases of high grade (pleomorphic) sarcomas diagnosed in adults above the age of 15 years in the section of histopathology at the Aga Khan University Hospital, Karachi during a period of two years. These high grade (pleomorphic) sarcomas were immunophenotyped using a panel including antibodies against Vimentin, Desmin, Smooth muscle Actin, S 100, CD34, CD68 and Cytokeratin etc by indirect immunoperoxidase.

Results: Of the 134 cases which were characterized, 38.1% were pleomorphic leiomyosarcoma, followed by pleomorphic rhabdomyosarcoma 14.9%, Malignant Peripheral Nerve Sheath Tumour 9%, pleomorphic liposarcoma 3.7% and pleomorphic storiform Malignant Fibrous Histiocytoma 0.7%. Thirty three percent of cases could not be characterized further. Mean/ median age for Leiomyosarcoma was 50/50, for Rhabdomyosarcomas 33/22, for MPNST 42/41, for Liposarcoma 52/50 and for Malignant Fibrous Histiocytoma 46/46 respectively. The commonest site for leiomyosarcoma was lower limb (43%), for rhabdomyosarcoma head and neck (42%), for MPNST thorax (36.4%) and for liposarcoma abdomen (50%).

Conclusion: It was concluded that the most common pleomorphic sarcoma occurring in our adult population was Leiomyosarcoma, and that immunohistochemical stains are essential in most cases for further characterization of pleomorphic high grade sarcoma (JPMA 55:101;2005).

Pleomorphic sarcoma are malignant neoplasms of mesenchymal origin showing varying differentiation and composed of pleomorphic cells with or without abundant eosinophilic or fibrillary cytoplasm in most areas.1 These include Pleomorphic leiomyosarcoma (PLMS), Pleomorphic rhabdomyosarcoma (PRMS), Pleomorphic liposarcoma (PLS), Pleomorphic malignant nerve sheath tumour (PMNST), Malignant fibrous histiocytoma storiform pleomorphic type (MFH).

Adult pleomorphic sarcomas are a relatively uncommon group of tumors that have inherent difficulties in diagnosis because of morphologic similarities.2 With the development of more sophisticated ancillary studies, the pleomorphic sarcomas have been recognized as encompassing a heterogenous group of tumors expressing features that could be classified more specifically with the use of immunohistochemistry or molecular studies. Close reexamination of older series of pleomorphic sarcomas allows reclassification of more than half of those cases into a more specific diagnostic category.3,4 As a consequence, pleomorphic rhabdomyosarcoma and liposarcoma are reportedly increasing in incidence and MFH is becoming a less commonly diagnosed entity. It was over these years, that a better insight into the age, sex and site distribution of these tumours was obtained.

Further characterization of pleomorphic sarcomas is important as many studies found that in addition to tumour size, grade, and location, the tumor histologic type have prognostic and therapeutic implications.2

Unfortunately immunohistochemical stains are performed in very few institutions of Pakistan and diagnosis is made only on hematoxylin and eosin sections along with the help of history and clinical presentation. Diagnosis made only on hematoxylin and eosin sections of these pleomorphic sarcomas is very difficult as they are very similar morphologically, in spite of being distinct entities. As there is no data on these tumors in the Pakistani population, this study was undertaken to obtain the same.

This was a cross sectional descriptive study conducted at the Histopathology section of theDepartment of Pathology, Aga Khan University Hospital. The study used a questionnaire containing open ended and close ended questions. The sample was non probability purposive sample of 134 surgical specimens with the diagnosis of 'pleomorphic sarcoma'.

The specimens were grossed according to the guidelines given in surgical pathology by Ackermen.5 Representative sections taken were processed and then stained with haematoxylin and eosin. Special stains included PAS with and without diastase, Reticulin and Masson's tri-chrome.

The tumors were graded according to anaplasia, mitosis and tumor necrosis. Immunohistochemical workup was done for further characterization of the tumour and the antibodies included vimentin, desmin, alpha smooth muscle actin (ASMA), S100, CD34, CD68 and cytokeratins. Positive and negative controls were run in parallel with each new batch of staining.

Data was entered and analyzed using SPSS version 10.

Diagnostic Criteria

The following criteria were applied for diagnosis of the tumours.

Pleomorphic leiomyosarcoma

Pleomorphic leiomyosarcoma has been defined as co expressing both desmin and smooth muscle actin or actin alone. In addition, cases must show pleomorphic cells with abundant eosinophillic or fibrillary cytoplasm in more than two third of the maximum cut surface.4,6

Pleomorphic Rhabdomyosarcoma

For Pleomorphic rhabdomyosarcoma the following diagnostic criteria were used (a) pleomorphic spindle cell sarcoma occurring in voluntary muscle (b) the presence of large polygonal or strap -like cells with copious deeply eosinophillic cytoplasm and (c) the demonstration in tumour cells of desmin immunoreactivity.7

Pleomorphic Liposarcoma

The single criterion for the dagnosis of pleomorphic liposarcoma was the presence of multivacuolated lipoblasts, which were defined as large cells containing at least two clearly defined intra cytoplasmic vacuoles that distended the cells in such a way that often no other cytoplasm was evident. These vacuoles had sharply circumscribed, non overlapping margins that indented the nuclei. The nuclei are usually eccentric, densely hyper chromatic, variably pleomorphic and had a "punched out" out line due to the vacuolar indentations.4,8

Pleomorphic Malignant Peripheral Nerve Sheath Tumour (MPNST)

Diagnostic criteria used were (a) demonstrable origin from a major nerve, (b) demonstrable origin in a preexistent benign nerve sheath tumor, (c) S-100 positivity.4

Pleomorphic MFH

Diagnostic criteria for storiform pleomorphic sarcoma were (a) plump spindle shaped cells arranged to form a mixture of storiform and pleomorphic areas, (b) positivity for vimentin and CD68 stain.3,9

Unclassifiable pleomorphic sarcoma

These were group of tumors in which, despite the use of clinical data, and immunohistochemistry, a definable line of differentiation could not be identified . The sole remaining criterion was therefore a pleomorphic sarcomatoid morphology with clear evidence of malignancy.4

Out of 134 cases which were characterized, 38.1% were pleomorphic leiomyosarcoma, followed by pleomorphic rhabdomyosarcoma 14.9%, Malignant Peripheral Nerve Sheath Tumour 9%, pleomorphic liposarcoma 3.7% and pleomorphic storiform Malignant Fibrous Histiocytoma 0.7%. Thirty three percent of cases could not be characterized further. Mean/median age for

Table 1. Age distribution of pleomorphic sarcomas.
Diagnosis	Mean	Median	Minimum	Maximum
PLMS	49.78	50.00	18	80
PRMS	32.78	22.00	14	65
PLPS	46.40	50.00	18	74
MPNST	42.82	45.00	18	60
MFH	46.00	46.00	46	46
NOS	50.00	50.00	15	80
Total	46.78	48.00	14	80

Table 2. Site distribution of pleomorphic sarcomas.
SITE	PLMS	PRMS	PLPS	MPNST	MFH	NOS
	%	%	%	%	%	%
Head and neck	13.7	45.0		8.3		11.1
Upper limb	7.8			8.3		11.1
Thorax	5.9	10.0		33.3		13.3
Abdomen	17.6	5.0	60.0	16.7		11.1
Pelvis	9.8	30.0		8.3		8.9
Lowerlimb	45.1	10.0	40.0	25.0	100.0	44.4
Total	100.0	100.0	100.0	100.0	100.0	100.0

[(0)]

Leiomyosarcoma was 50/50, for Rhabdomyosarcoma 33/22, for MPNST 42/41, for Liposarcoma 52/50 and for Malignant Fibrous Histiocytoma 46/46 respectively (Table 1). The commonest site for leiomyosarcoma was lower limb (43%), for rhabdomyosarcoma, head and neck (42%), for MPNST, thorax (36.4%) and for liposarcoma, abdomen (50%) (Table 2).

The history of pleomorphic sarcoma could be divided into three periods. The first period starts from 1948 to 1970. During this period the concept that pleomorphic RMS represent a unique and relatively common adult soft tissue sarcoma appeared to gain acceptance.10-12

The second period overlapped with the antecedent and marked the emergence of MFH. Through this time the concept of MFH flourished. In fact, some plemorphic RMS included in large retrospective series were reclassified as pleomorphic variant of MFH.1 and the pleomorphic variant of RMS came to be regarded as exteremely rare or non existent.10-15

The third period again overlapping with the previous period began in the 1980, through the progressive application of immunohistochemical techniques in the diagnosis of soft tissue sarcoma. During this period Most of the cases previously diagnosed as MFH were reexamined, and its existence was questioned.16-18

There can be no dispute that immunohistochemical, biochemical, and molecular characterization in conjunction with the clinical details and morphology , has greatly facilitated the diagnosis, which at one time was extremely cumbersome.12,17,18

Following the adoption of immunohistochemical staining techniques many studies were carried out to re-diagnose the cases previously diagnosed as high grade sarcoma. Among these the work of Christofer DM Fletcher is remarkable, who reassessed critically a large group of tumors diagnosed as pleomorphic sarcoma of any type. He defined criteria for diagnosing these sarcomas. His study shows that 25% of pleomorphic sarcomas were diagnosed as liposarcoma, followed by leiomysarcoma 18.2%, rhabdomyosarcoma 6.3%, MPNST 3.1%, MFH and unclassifiable; MFH collectively were 26.4%.4 After this study there have been several reports where a series of various pleomorphic sarcomas were studied using the same diagnostic criteria as used by Fletcher.These studies showed that leiomyosarcoma occurred in the age range of 34 -75 years (mean, 57.9 and median, 59 years), 60% of cases occurred in extremities, 25% were located in the retroperitoneum or abdominal cavity, 11% were located in the chest/abdominal wall or back.4,6,15,19 The pleomorphic rhabdomyosarcoma occurred in the age range of 31-84 years with median of 57 years. The common sites of Pleomorphic rhabdomyosarcoma were thigh, trunk, and retroperitoneum.2,4,7,20 MPNST occurred in adults with mean age of 61.4 years. Thigh, thorax and neck region were the common sites.4,21 The liposarcoma occurred in age range of 16-88 years (median 57 years), at lower extremities followed by upper extremities and retroperitoneum.4,8 The unclassified group had an age group range of 16-85 years and originated in lower limb/girdle, trunk, head and neck.4,22 23

Using the same diagnostic criteria as mentioned above we characterized the pleomorphic sarcomas in our adult population and found similar results as mentioned above with the exception that leiomyosarcoma was the most common malignant mesenchymal tumour followed by Rhabdomyosarcoma. Liposarcoma in our study was uncommon. The distribution of age and site was also similar as given above.

In conclusion the most common pleomorphic sarcoma occurring in our adult population was Leiomyosarcoma, and that immunohistochemical stains are essential in most cases for further classification of pleomorphic high grade sarcomas.

1. Schurch W, Begin LR, Seemayer TA, Lagace R, Boivin JC, Lamoureux C, et al. Pleomorphic soft tissue myogenic sarcomas of adulthood: a reappraisal in the mid-1990s. Am J Surg Pathol 1996;20:131-47.

2. Deyrup AT, Haydon RC, Huo D, Ishikawa A, Peabody TD, He TC, et al. Myoid differentiation and prognosis in adult pleomorphic sarcomas of the extremity: an analysis of 92 cases. Cancer 2003;98:805-13.

3. Fletcher CD, Gustafson P, Rydholm A, Willen H, Akerman M. Clinicopathologic re-evaluation of 100 malignant fibrous histiocytomas: prognostic relevance of subclassification. J Clin Oncol 2001;19:3045-50.

4. Fletcher CD. Pleomorphic malignant fibrous histiocytoma: fact or fiction? a critical reappraisal based on 159 tumors diagnosed as pleomorphic sarcoma. Am J Surg Pathol 1992;16:213-8.

5. Juan R. Guidelines for handling of most common and important surgical specimens.In: Juan R. Surgical pathology. 8th ed. New York: Mosby, 1996, pp 2652-3.

6. Oda Y, Miyajima K, Kawaguchi K, Tamiya S, Oshiro Y, Hachitanda Y, et al. Pleomorphic leiomyosarcoma: clinicopathologic and immunohistochemical study with special emphasis on its distinction from ordinary leiomyosarcoma and malignant fibrous histiocytoma. Am J Surg Pathol 2001;25:1030-38.

7. Gaffney EF, Dervan PA, Fletcher CD. Pleomorphic rhabdomyosarcoma in adulthood. Analysis of 11 cases with definition of diagnostic criteria. Am J Surg Pathol 1993;17:601-9.

8. Oliveira AM, Nascimento AG. Pleomorphic liposarcoma. Semin Diagn Pathol 2001;18:274-85.

9. Meister P, Konrad E, Hohne N. Incidence and histological structure of the storiform pattern in benign and malignant fibrous histiocytomas. Virchows Arch A Pathol Anat Histol 1981;393:93-101.

10. Ariel IM, Briceno M. Rhabdomyosarcoma of the extremities and trunk: analysis of 150 patients treated by surgical resection. J Surg Oncol 1975;7:269-87.

11. Keyhani A, Booher RJ. Pleomorphic rhabdomyosarcoma. Cancer 1968;22:956-67.

12. Hameed A, Sarwar G. Clinico-Pathological Features of Soft Tissue Sarcoma (STS).Ann King Edward Med Coll 1999;5:80-2.

13. Weiss SW, Enzinger FM. Malignant fibrous histiocytoma: an analysis of 200 cases. Cancer 1978;41:2250-66.

14. Weiss SW. Malignant fibrous histiocytoma. A reaffirmation. Am J Surg Pathol 1982;6:773-84.

15. Fahim F. Leiomyosarcomas: analysis of clinical presentations in 6 patients.J Pak Med Assoc 2002;52:412-14.

16. Schurch W, Skalli O, Lagace R, Seemayer TA, Gabbiani G. Intermediate filament proteins and actin isoforms as markers for soft-tissue tumor differentiation and origin. III. Hemangiopericytomas and glomus tumors. Am J Pathol 1990;136:771-86.

17. Skalli O, Gabbiani G, Babai F, Seemayer TA, Pizzolato G, Schurch W. Intermediate filament proteins and actin isoforms as markers for soft tissue tumor differentiation and origin. II. Rhabdomyosarcomas. Am J Pathol 1988;130:515-31.

18. Schurch W, Skalli O, Seemayer TA, Gabbiani G. Intermediate filament proteins and actin isoforms as markers for soft tissue tumor differentiation and origin. I. Smooth muscle tumors. Am J Pathol 1987;128:91-103.

19. Talati N, Pervez S. Soft tissue sarcomas: pattern diagnosis or entity? J Pak Med Assoc 1998;48:272-5.

20. Bhurgri Y, Bhurgri A, Puri R, Ashraf S, Qidwai A, Ashraf K, et al. Rhabdomyosarcoma in Karachi 1998-2002. Asian Pac J Cancer Prev 2004;5:284-90.

21. Laskin WB, Weiss SW, Bratthauer GL. Epithelioid variant of malignant peripheral nerve sheath tumor (malignant epithelioid schwannoma). Am J Surg Pathol 1991;15(12):1136-45.

22. Iskandar SS, Cappellari JO. Malignant fibrous histiocytoma phenotype in pleomorphic sarcoma differentiation in recurrent disease. Arch Pathol Lab Med 1995;119:113-15.

23. Costa MJ. Malignant fibrous histiocytoma phenotype in pleomorphic sarcoma differentiation in recurrent disease. Arch Pathol Lab Med 1994;118:160-4.