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. 2022 Jan;10(1):67–77. doi: 10.22038/ABJS.2021.53750.2676

Soft Tissue Sarcoma of Extremities: Descriptive Epidemiological Analysis According to National Population-based Study

Adel Ebrahimpour 1,2,5, Mohammadreza Chehrassan 1,2, Mehrdad Sadighi 1,2, Amin Karimi 3, Mehdi Azizmohammad Looha 4, Meisam Jafari Kafiabadi 1,2
PMCID: PMC8889428  PMID: 35291240

Abstract

Background:

Soft-Tissue Sarcoma (STS) is a heterogeneous group of neoplasms of mesenchymal origin, occurring in connective tissues. According to previously conducted studies, STS accounts for approximately 1% and 7-%15% of adult and pediatric malignancies, respectively. Almost 50%-60% of sarcomas arise from extremities and usually present as a large painless or rarely painful soft-tissue mass. The present study aimed to describe the epidemiology of soft-tissue sarcomas, especially in the Iranian population.

Methods:

This epidemiological study of limb soft-tissue sarcoma was conducted based on Iran National Cancer Registry data (INCR) between 2009 and 2014. Patients with soft-tissue sarcoma confirmed by histopathological studies were included, and data were classified based on the International Classification of Diseases for Oncology (first revision-third edition [ICD-O-3]) and analyzed. Descriptive analysis was performed to extract age-standardized and age-specific incidence rates.

Results:

A total of 2, 593 patients (1,476 males and 1,117 females) were enrolled and assessed in the present study. The age-standardized incidence rate(ASIR) of total soft tissue sarcomas was 6.34 per million person-years. In addition, the highest and lowest ASIR scores stratified by age were observed in patients aged above 65 and under 0 with the value of 19.61 (95% CI:17.91-21.30) and 1.91 (95% CI 1.69, 2.13) per million, respectively. Limb soft tissue sarcomas stratified by gender were dominant in males, and it was statistically significant (P<0.05). The most common extremity soft tissue sarcomas subtypes were mesenchymal tumor (12.26%), spindle cell sarcoma (12.18%), and malignant fibrous histiocytoma (11.45%).

Conclusion:

As evidenced by the results of the present study, the ASIR of soft tissue sarcoma dramatically increased with age, and the peak ASIR occurred in the age range of above 65 years. The incidence rate of soft tissue sarcomas analyzed by disease site was higher in hip and lower limb than upper limb and pelvis region, and it was detected consistently in all age groups and both genders.

Key Words: Sarcoma, Soft Tissue, Extremities, Soft Tissue Neoplasm

Introduction

Soft-Tissue Sarcoma (STS) is a heterogeneous group of neoplasms occurring in connective tissues. According to previous studies, STS accounts for 1% and 7%-15% of adult and pediatric malignancies, respectively (1,2). Almost 50%-60% of sarcomas arise from extremities and usually present as a large painless or rarely painful soft-tissue mass (2,3). About 8,000 new STS cases occur each year in the United States, leading to a higher death rate, as compared to testicular cancer, Hodgkin’s disease, and thyroid cancer (3,4). These tumors are challenging to treat due to recurrences and metastases despite apparently complete resection with negative margins, bringing about devastating results (2).

A better appreciation of incidence and treatment patterns of STS is critical to consider the impact of STS on public health. Due to its exiguity, a few cases of STS are referred to and diagnosed even in specialized sarcoma centers. Therefore, a large population-based study would be of great help in the evaluation of its incidence and treatment pattern. On the other hand, inattention to these lesions can end in limb loss, morbidity, and even mortality

There are a few population-based studies on STS, reporting the incidences between 1.8 and 5.0 cases per 100,000 people per year (5–9). Nevertheless, the majority of these studies were based on Western populations, and there is a paucity of information about the Asian population, particularly in middle-east people. Furthermore, most of the studies included the STS of all anatomical sites, whereas the treatment and prognoses of STS differ according to the anatomical location (e.g., head and neck, viscera, retroperitoneum, and extremity) (9). In Iran, there is no population-based study on the incidence of soft tissue tumors; therefore, it is required to investigate the incidence and treatment patterns of extremity STS in Iran according to a population-based study. The knowledge of local epidemiologic parameters of these tumors can be effective in better diagnosis and treatment of extremity tumors, and accordingly, the improvement of the general health of the Iranian population.

Materials and Methods

This population-based epidemiological study of limb soft-tissue sarcoma was conducted based on the Iranian National Cancer Registry (INCR) data between January 2009 and December 2014. Patients with soft-tissue sarcoma confirmed by histopathological studies were included and data were classified and analyzed. In addition, data were categorized based on the International Classification of Diseases for Oncology (first revision-third edition [ICD-O-3]) and M-Codes.

All the recorded cases in INCR with a diagnosis of limb soft-tissue sarcoma between 2009 and 2014 were collected. Out of the 2,913 subjects, 103 cases were ruled out due to incorrect histology codes, missing data, and non-Iranian nationality. Furthermore, 217 cases were excluded after duplicate extraction [Table 1].

Table 1.

Percentage of Data Extraction

Year Before Duplicate Extraction After Duplicate Extraction Percentage
2009 379 379 0.00
2010 339 339 0.00
2011 512 465 9.18
2012 578 492 14.88
2013 534 455 14.79
2014 468 463 1.07
Total 2810 2593 7.72
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A number of 2,593 cases (1,476 men and 1,117 women) were included in the study and categorized into histopathological groups and subgroups based on their M-codes [Table 2]. We did not consider histological assessments and grading due to incomplete histopathological records and the lack of histology codes on INCR.

Table 2.

Incidence (per million person-years) of Primary Soft Tissue Sarcomas by Sex and Histologic Subtype, Iran (2009-2014)

Histologic Subtype Sex n Crude Rate ASR* 95% CI SRR 95% CI
Total Both sexes 2593 5.73 6.34 6.09-6.59
Male 1476 6.45 7.19 6.82-7.57 1.31** 1.21-1.42
Female 1117 4.99 5.47 5.15-5.80
Paragangliomas and Glomous Tumors Both sexes 1 <0.01 <0.01 -----
Male 1 <0.01 0.01 ----- ----- -----
Female 0 <0.01 <0.01 -----
Glomangiosarcoma Both sexes 1 <0.01 <0.01 -----
Male 1 <0.01 0.01 ----- ----- -----
Female 0 <0.01 <0.01 -----
Soft Tissue Sarcomas, NOS Both sexes 840 1.86 2.08 1.94-2.23
Male 475 2.08 2.35 2.14-2.57 1.30** 1.13-1.49
Female 365 1.63 1.81 1.62-2.00
Mesenchymal tumor Both sexes 318 0.70 0.81 0.71-0.90
Male 174 0.76 0.88 0.75-1.02 1.21 0.96-1.52
Female 144 0.64 0.73 0.61-0.85
Spindle cell sarcoma Both sexes 316 0.70 0.78 0.69-0.86
Male 190 0.83 0.94 0.80-1.07 1.53** 1.21-1.92
Female 126 0.56 0.61 0.50-0.72
Giant cell sarcoma/pleomorphic cell sarcoma Both sexes 113 0.25 0.30 0.24-0.35
Male 60 0.26 0.32 0.24-0.40 1.18 0.18-1.72
Female 53 0.24 0.27 0.20-0.34
Small cell sarcoma/round cell sarcoma Both sexes 17 0.04 0.04 0.02-0.06
Male 10 0.04 0.05 0.02-0.08 1.37 0.51-3.73
Female 7 0.03 0.03 0.01-0.06
Epithelioid sarcoma Both sexes 38 0.08 0.08 0.05-0.11
Male 23 0.10 0.09 0.05-0.13 1.33 0.69-2.56
Female 15 0.07 0.07 0.03-0.10
Undifferentiated sarcoma Both sexes 20 0.04 0.05 0.02-0.07
Male 10 0.04 0.05 0.02-0.08 0.86 0.35-2.12
Female 10 0.04 0.05 0.02-0.09
Desmoplastic round cell tumor Both sexes 18 0.04 0.04 0.02-0.06
Male 8 0.03 0.03 0.01-0.06 0.79 0.30-2.05
Female 10 0.04 0.04 0.02-0.07
Fibromatous Sarcomas Both sexes 486 1.07 1.23 1.12-1.35
Male 274 1.20 1.38 1.22-1.55 1.28** 1.07-1.54
Female 212 0.95 1.08 0.93-1.23
Fibrosarcoma Both sexes 114 0.25 0.26 0.21-0.31
Male 61 0.27 0.29 0.21-0.36 1.20 0.82-1.75
Female 53 0.24 0.24 0.17-0.31
Fibromyxosarcoma Both sexes 24 0.05 0.06 0.03-0.08
Male 8 0.03 0.04 0.01-0.08 0.61 0.26-1.40
Female 16 0.07 0.07 0.04-0.11
Infantile/congenital fibrosarcoma Both sexes 6 0.01 0.01 0.00-0.03
Male 3 0.01 0.01 0.00-0.03 ----- -----
Female 3 0.01 0.01 0.00-0.03
Solitary fibrous tumor Both sexes 3 0.01 0.01 0.00-0.02
Male 1 <0.01 <0.01 0.00-0.01 ----- -----
Female 2 0.01 0.01 0.00-0.03
Fibrous histiocytoma/fibroxanthoma Both sexes 297 0.66 0.80 0.71-0.89
Male 177 0.77 0.93 0.79-1.08 1.42** 1.12-1.79
Female 120 0.54 0.66 0.54-0.78
Dermatofibrosarcoma Both sexes 42 0.09 0.09 0.06-0.12
Male 24 0.10 0.10 0.06-0.14 1.26 0.68-2.34
Female 18 0.08 0.08 0.04-0.12
Myxomatous Sarcomas Both sexes 5 0.01 0.01 0.00-0.03
Male 3 0.01 0.02 0.00-0.04 ----- -----
Female 2 0.01 0.01 0.00-0.02
Myxosarcom Both sexes 5 0.01 0.01 0.00-0.03
Male 3 0.01 0.02 0.00-0.04 ----- -----
Female 2 0.01 0.01 0.00-0.02
Lipomatous Sarcomas Both sexes 370 0.82 0.92 0.83-1.02
Male 203 0.89 1.01 0.87-1.15 1.21 0.98-1.49
Female 167 0.75 0.83 0.70-0.96
Liposarcoma/fibroliposarcoma Both sexes 77 0.17 0.19 0.15-0.24
Male 39 0.17 0.20 0.14-0.27 1.09 0.69-1.72
Female 38 0.17 0.18 0.12-0.24
Liposarcoma, well differentiated Both sexes 50 0.11 0.13 0.09-0.17
Male 24 0.10 0.12 0.07-0.17 0.92 0.52-1.63
Female 26 0.12 0.13 0.08-0.19
Myxoid Liposarcoma Both sexes 163 0.36 0.39 0.33-0.45
Male 93 0.41 0.44 0.35-0.53 1.28 0.93-1.76
Female 70 0.31 0.34 0.26-0.42
Round cell liposarcoma Both sexes 19 0.04 0.04 0.02-0.06
Male 12 0.05 0.06 0.02-0.09 1.86 0.72-4.81
Female 7 0.03 0.03 0.01-0.05
Pleomorphic liposarcoma Both sexes 40 0.09 0.11 0.08-0.15
Male 22 0.10 0.12 0.07-0.18 1.23 0.68-2.42
Female 18 0.08 0.10 0.05-0.14
Mixed liposarcoma Both sexes 11 0.02 0.03 0.01-0.04
Male 8 0.03 0.04 0.01-0.06 2.30 0.64-8.23
Female 3 0.01 0.02 0.00-0.04
Fibromyxosarcoma Both sexes 24 0.05 0.06 0.03-0.08
Male 8 0.03 0.04 0.01-0.08 0.61 0.26-1.40
Female 16 0.07 0.07 0.04-0.11
Infantile/congenital fibrosarcoma Both sexes 6 0.01 0.01 0.00-0.03
Male 3 0.01 0.01 0.00-0.03 ----- -----
Female 3 0.01 0.01 0.00-0.03
Solitary fibrous tumor Both sexes 3 0.01 0.01 0.00-0.02
Male 1 <0.01 <0.01 0.00-0.01 ----- -----
Female 2 0.01 0.01 0.00-0.03
Fibrous histiocytoma/fibroxanthoma Both sexes 297 0.66 0.80 0.71-0.89
Male 177 0.77 0.93 0.79-1.08 1.42** 1.12-1.79
Female 120 0.54 0.66 0.54-0.78
Dermatofibrosarcoma Both sexes 42 0.09 0.09 0.06-0.12
Male 24 0.10 0.10 0.06-0.14 1.26 0.68-2.34
Female 18 0.08 0.08 0.04-0.12
Myxomatous Sarcomas Both sexes 5 0.01 0.01 0.00-0.03
Male 3 0.01 0.02 0.00-0.04 ----- -----
Female 2 0.01 0.01 0.00-0.02
Myxosarcom Both sexes 5 0.01 0.01 0.00-0.03
Male 3 0.01 0.02 0.00-0.04 ----- -----
Female 2 0.01 0.01 0.00-0.02
Lipomatous Sarcomas Both sexes 370 0.82 0.92 0.83-1.02
Male 203 0.89 1.01 0.87-1.15 1.21 0.98-1.49
Female 167 0.75 0.83 0.70-0.96
Liposarcoma/fibroliposarcoma Both sexes 77 0.17 0.19 0.15-0.24
Male 39 0.17 0.20 0.14-0.27 1.09 0.69-1.72
Female 38 0.17 0.18 0.12-0.24
Liposarcoma, well differentiated Both sexes 50 0.11 0.13 0.09-0.17
Male 24 0.10 0.12 0.07-0.17 0.92 0.52-1.63
Female 26 0.12 0.13 0.08-0.19
Myxoid Liposarcoma Both sexes 163 0.36 0.39 0.33-0.45
Male 93 0.41 0.44 0.35-0.53 1.28 0.93-1.76
Female 70 0.31 0.34 0.26-0.42
Round cell liposarcoma Both sexes 19 0.04 0.04 0.02-0.06
Male 12 0.05 0.06 0.02-0.09 1.86 0.72-4.81
Female 7 0.03 0.03 0.01-0.05
Pleomorphic liposarcoma Both sexes 40 0.09 0.11 0.08-0.15
Male 22 0.10 0.12 0.07-0.18 1.23 0.68-2.42
Female 18 0.08 0.10 0.05-0.14
Mixed liposarcoma Both sexes 11 0.02 0.03 0.01-0.04
Male 8 0.03 0.04 0.01-0.06 2.30 0.64-8.23
Female 3 0.01 0.02 0.00-0.04
Carcinosarcoma Both sexes 1 <0.01 <0.01 ------
Male 0 <0.01 <0.01 ------ ------ ------
Female 1 <0.01 <0.01 ------
Mixed mesenchymal sarcoma Both sexes 6 0.01 0.02 0.00-0.03
Male 4 0.02 0.02 0.00-0.04 ------ ------
Female 2 0.01 0.01 0.00-0.02
Synovial Like Sarcomas Both sexes 353 0.78 0.79 0.71-0.88
Male 205 0.90 0.92 0.79-1.06 1.40** 1.13-1.74
Female 148 0.66 0.66 0.55-0.77
Synovial sarcoma, NOS Both sexes 184 0.41 0.42 0.35-0.48
Male 106 0.45 0.48 0.39-0.58 1.38** 1.02-1.86
Female 78 0.35 0.35 0.27-0.43
Synovial sarcoma, spindle cell Both sexes 79 0.17 0.17 0.13-0.21
Male 49 0.21 0.22 0.16-0.29 1.72** 1.08-2.75
Female 30 0.13 0.13 0.08-0.18
Synovial sarcoma, epithelioid cell Both sexes 4 0.01 0.01 0.00-0.02
Male 1 <0.01 <0.01 0.00-0.01 ------ ------
Female 3 0.01 0.01 0.00-0.03
Synovial sarcoma, biphasic Both sexes 60 0.13 0.13 0.10-0.16
Male 33 0.14 0.14 0.09-0.19 1.19 0.71-2.01
Female 27 0.12 0.12 0.07-0.16
Clear cell sarcoma of tendons and aponeuroses, melanoma Both sexes 26 0.06 0.06 0.04-0.08
Male 16 0.07 0.07 0.04-0.11 1.51 0.67-3.39
Female 10 0.04 0.05 0.02-0.08
Blood Vessels Sarcomas Both sexes 61 0.13 0.16 0.12-0.21
Male 38 0.17 0.21 0.14-0.28 1.72** 1.02-2.91
Female 23 0.10 0.12 0.07-0.17
Haemangiosarcoma Both sexes 22 0.05 0.06 0.03-0.09
Male 8 0.03 0.04 0.01-0.08 0.57 0.24-1.38
Female 14 0.06 0.08 0.04-0.12
Hemangioendothelial sarcoma Both sexes 3 0.01 0.01 0.00-0.02
Male 2 0.01 0.01 0.00-0.02 ------ ------
Female 1 0.00 <0.001 ------
Kaposi sarcoma Both sexes 29 0.06 0.08 0.05-0.11
Male 24 0.10 0.13 0.08-0.19 5.32** 2.15-13.15
Female 5 0.02 0.03 0.00-0.05
Malignant Haemangiopericytoma Both sexes 7 0.02 0.02 0.00-0.03
Male 4 0.02 0.02 0.00-0.04 1.43 0.31-6.60
Female 3 0.01 0.01 0.00-0.03
Lymphatic Vessels Sarcomas Both sexes 2 <0.001 0.01 0.00-0.01
Male 1 <0.001 0.01 0.00-0.02 ------ ------
Female 2 0.01 0.01 0.0-0.03
Lymphangiosarcoma Both sexes 2 <0.001 0.01 0.00-0.01
Male 1 <0.001 0.01 0.00-0.02 ------ ------
Female 2 0.01 0.01 0.0-0.03
Giant Cell Tumors-Malignant Both sexes 44 0.10 0.10 0.07-0.14
Male 23 0.10 0.11 0.06-0.15 1.03 0.56-1.88
Female 21 0.09 0.10 0.06-0.15
Malignant giant cell tumor of soft parts Both sexes 19 0.04 0.04 0.02-0.06
Male 14 0.06 0.06 0.03-0.10 2.83** 1.04-7.72
Female 5 0.02 0.02 0.00-0.04
Malignant tenosynovial giant cell tumor Both sexes 25 0.06 0.06 0.04-0.09
Male 9 0.04 0.04 0.01-0.07 0.52 0.23-1.19
Female 16 0.07 0.08 0.04-0.12
Nerve Sheath Tumors-Malignant Both sexes 96 0.21 0.22 0.18-0.27
Male 66 0.29 0.30 0.22-0.37 2.09** 1.36-3.21
Female 30 0.13 0.14 0.09-0.20
Malignant peripheral nerve sheath tumor Both sexes 91 0.20 0.21 0.17-0.25
Male 63 0.28 0.28 0.21-0.36 2.10** 1.35-3.26
Female 28 0.13 0.14 0.08-0.19
malignant schwannoma, Neurilemmosarcoma Both sexes 3 0.01 0.01 0.00-0.02
Male 1 <0.001 <0.001 ------ ------ ------
Female 2 0.01 0.01 0.00-0.02
Malignant peripheral nerve sheath tumor Both sexes 2 <0.001 <0.001 ------
Male 2 0.01 0.01 0.00-0.02 ------ ------
Female 0 <0.001 <0.001 ------
Granular cell and Alveolar Soft Tissue Sarcoma Both sexes 21 0.05 0.04 0.02-0.06
Male 10 0.04 0.04 0.01-0.06 0.82 0.34-1.97
Female 11 0.05 0.05 0.02-0.08
Alveolar soft part sarcoma Both sexes 21 0.05 0.04 0.02-0.06
Male 10 0.04 0.04 0.01-0.06 0.82 0.34-1.97
Female 11 0.05 0.05 0.02-0.08
Ewing tumor and Askin tumor of soft tissue Both sexes 68 0.15 0.14 0.11-0.17
Male 42 0.18 0.17 0.12-0.22 1.44 0.88-2.35
Female 26 0.12 0.12 0.07-0.16
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ASIR = age-standardized incidence rate, CI = confidence interval, NOS = not otherwise specified

SRR = male-to-female standardized incidence rate (ASIR) ratio

*ASRs were age-standardized to the new world health organizing (WHO) standard population

** Indicates statistical significance at the 0.05 level

The histopathological name of tumors was extracted from M-Codes. Due to incomplete histopathology registration of the patients and lack of histology codes on INCR, histology evaluation was completely excluded from this study. For each tumor subtype, the patients were classified based on age and gender. In each subgroup, the crude incidence rate, age-specific incidence rate, male to female standardized incidence rate ratio, and truncated Age-Standardized Incidence Rate (ASIR) with 95% confidence interval were calculated and recorded. All analyses were performed using R (version 3.6.3) and SPSS software (version 26) programs. A p-value less than<0.05 was considered statistically significant.

Results

In general, limb soft-tissue sarcomas were dominant in males. The ASIR was 7.19 in males versus 5.47 per million person-years (95% C. I: 0.20-0.30) in females, and the male-to-female standardized incidence rate ratio (SRR) was 1.31 per million person-years, and it was statistically significant (P<0.05) [Table 2]. The overall male gender dominancy was observed in most age subgroups with the most considerable difference in age subgroups 80-84 years [Figure 1]. As illustrated in Table 2, the female higher prevalence was observed in a few groups; nonetheless, none of them was statistically significant.

Figure1.

Figure1

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Incidence rates (per million) of primary soft tissue cancers in special age groups with topography subtypes and by gender in Iran from 2009 to 2014

The male-to-female SRR was statistically significant in five groups of sarcomas, including soft tissue sarcomas Not Otherwise Specified (NOS), fibromatous sarcomas, synovial sarcomas, blood vessels sarcomas, and malignant nerve sheath tumors. Among the major groups, the highest SRR belonged to malignant nerve sheath tumors (2.09 cases per million person-years). Among the subgroups, Kaposi sarcoma, malignant giant cell tumor of soft parts, pleomorphic rhabdomyosarcoma, and malignant peripheral nerve were more significant in male prevalence with SPR of more than 2 per million person-years [Table 2].

Among the major groups, after the group “NOS sarcomas (32.39%), the most common limb soft tissue sarcomas were Fibromatous sarcomas (18.74%), Lipomatous sarcomas (14.26%), Synovial like sarcomas (13.61%), and myomatous sarcomas (9.17%). In the group of NOS sarcomas, Mesenchymal tumors and Spindle cell sarcomas were more common than other subgroups, accounting for 12.26% and 12.18% of all soft tissue sarcomas, respectively. Fibrous histiocytoma and fibrosarcoma were the most common fibromatous sarcomas. Leiomyosarcoma and myxoid liposarcoma were more prevalent sequentially in myomatous and lipomatous sarcomas groups.

The obtained results pointed to an exponential increase in the incidence rate of soft tissue sarcoma with age. The same results were obtained in the four most common major groups [Figure 1]. In both males and females, the highest incidence rates of soft-tissue sarcoma per million person-years were reported as at 19.61 during 2009-2015 (95% CI 17.91-21.30) [Table 3].

Table3.

Incidence rates of soft-tissue sarcoma per million person-years during 2009-2015 in Iran, stratified by age and gender (CI: confidence interval, ASR*: truncated age-standardized incidence rate)

Age (Years) n Crude Rate ASR* (95% CI)
Both Sexes
<20 286 1.95 1.91 (1.69-2.13)
20-44 931 4.52 4.64 (4.34-4.94)
45-64 855 11.57 11.81 (11.01-12.60)
65+ 521 19.88 19.61 (17.91-21.30)
Male
<20 143 1.91 1.87 (1.56-2.18)
20-44 537 5.167 5.26 (4.81-5.71)
45-64 472 12.84 13.15 (11.96-14.35)
65+ 324 24.69 24.12 (21.47-26.77)
Female
<20 143 1.99 1.94 (1.63-2.26)
20-44 394 3.87 4.00 (3.61-4.40)
45-64 383 10.32 10.49 (9.43-11.54)
65+ 197 15.07 15.03 (12.92-17.13)
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The age-standardized incidence rates in the five most common major groups were reported as 2.08, 1.23, 0.92, 0.79, 0.59 for soft tissue NOS, fibromatous, lipomatous, synovial like, and myomatous sarcomas per million person-years, respectively.

In the soft tissue sarcomas NOS group, the highest ASIR belonged to mesenchymal tumors and spindle cell sarcomas with ratios of 0.81 and 0.78 per million person-years. In the fibromatous sarcomas group, malignant fibrous histiocytoma had a higher rate with an ASIR of 0.8 per million person-years. Myxoid liposarcoma with an ASR of 0.39 per million person-years was more frequent than the other subgroups. In synovial like sarcoma, synovial sarcoma NOS was more common with an ASR of 0.42, followed by synovial sarcoma spindle cell and biphasic synovial sarcoma. Finally, in the myomatous sarcomas group, leiomyosarcoma had the highest ASIR which was 0.378 per million person-years.

The incidence of soft-tissue sarcomas was assessed in three regions, including upper limb (C 49.1), hip and lower limb (C 49.2), as well as the pelvis (C 49.5) [Table 4]. The incidence rate in the hip and lower limb was totally higher, as compared to that in the upper limb and pelvis region, and it was confirmed in all gender and age groups. Especially in lipomatous sarcomas, the incidence rate of tumors in the lower limb was more than four times higher than that in the upper limb. On the contrary, the incidence rate of malignant giant cell tumors in the upper limb was higher than that in other areas [Table 4].

Table 4.

Incidence (per million person-years) of Primary Soft Tissue by Histologic Subtype and Topography subgroup, Iran (2009-2014)

Histology Subgroup C49.1 C49.2 C49.5
Total 15.41 (15.28-15.53) 36.70 (36.51-36.89) 10.30 (10.20-10.41)
Paragangliomas and Glomous Tumors 0.00 (0.00-0.00) 0.03 (0.02-0.03) 0.00 (0.00-0.00)
Soft Tissue Sarcomas, NOS 5.24 (5.17-5.31) 11.17 (11.06-11.27) 4.24 (4.18-4.31)
Fibromatous Sarcomas 3.32 (3.26-3.37) 7.45 (7.36-7.54) 1.41 (1.38-1.45)
Myxomatous Sarcomas 0.05 (0.04-0.05) 0.10 (0.08-0.11) 0.00 (0.00-0.00)
Lipomatous Sarcomas 1.34 (1.30-1.37) 6.09 (6.02-6.17) 1.72 (1.68-1.76)
Myomatous Sarcomas 1.31 (1.27-1.35) 2.68 (2.63-2.73) 1.54 (1.50-1.58)
Complex Mixed Sarcomas 0.05 (0.04-0.05) 0.13 (0.12-0.15) 0.02 (0.01-0.02)
Synovial Like Sarcomas 1.84 (1.80-1.88) 5.35 (5.28-5.42) 0.65 (0.63-0.67)
Blood Vessels Sarcomas 0.67 (0.64-0.70) 0.90 (0.86-0.93) 0.08 (0.07-0.09)
Lymphatic Vessels Sarcomas 0.03 (0.03-0.04) 0.03 (0.02-0.03) 0.00 (0.00-0.00)
Giant Cell Tumors-Malignant 0.73 (0.70-0.76) 0.22 (0.21-0.24) 0.03 (0.02-0.03)
Ewing tumor and Askin tumor of soft tissue 0.30 (0.29-0.32) 0.77 (0.74-0.79) 0.30 (0.28-0.31)
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Discussion

Soft tissue sarcomas are rare neoplastic lesions accounting for 1% of adult malignancies (1). Limb soft tissue sarcomas are even less frequent. According to previous studies, malignant fibrous histiocytoma was the most common soft tissue sarcoma in extremities with an incidence of 23%-24% (10–13). In another study, leiomyosarcoma was recognized as the most common and malignant fibrous histiocytoma as the second most common soft tissue sarcomas (8). According to a recent population-based study in Australia in 2019, leiomyosarcoma (20.43%), malignant fibrous histiocytoma (16.14%), and soft tissue tumors/sarcomas, and NOS (10.18%) were the most common STS subtypes(14).

In the present study, the most common soft tissue sarcomas of the extremities were mesenchymal tumor (12.26%), spindle cell sarcoma (12.18%), and malignant fibrous histiocytoma (11.45%) [Table 2]. This discrepancy in the results can be attributed to inaccurate and un-detailed histopathological classifications in the noted studies. In these studies, soft tissue sarcomas were not classified according to ICD-O3, and the major group of soft tissue sarcoma NOS were ignored. According to our database analysis, soft tissue sarcoma NOS include 32.39% of all extremity soft tissue sarcomas which was more frequent than other histopathological major groups. In their study, A. Gingrich et al. pointed out that most extremity soft tissue sarcomas in both nonelderly adult and elderly adult populations were soft tissue sarcoma NOS (15). They also used ICD-O3 to classify the tumors (15). In the current study, ignoring soft tissue sarcoma NOS, malignant fibrous histiocytomas (MFH) included 11.45% of soft tissue sarcomas. The other probable cause of contradictory results can be racial differences.

Gender dominancy was also observed in most groups and their subgroups, with men suffering much more often soft-tissue sarcomas [Table 2]. In some of the groups, this dominant ratio was statistically significant. Although female predominancy in the incidence ratio of tumors was detected in a few groups, they were not statistically significant. In general, the SRR was 1.31 in a total of 2,593 cases of soft-tissue sarcoma. Although some reports indicated that STS involved both genders with approximately equal ratios (13,16), some other studies revealed male dominancy among STS patients (13,16). According to Parker et al., soft-tissue sarcoma was more frequent in men, and deaths due to STS were more frequent in females (17). On the contrary, Reshadi et al. reported a higher prevalence of STS in the female population(10).

As illustrated by the results, the incidence rates (per million) of soft-tissue sarcoma increased with age in total cases and by subgroups [Table 3]. The incidence rates (per million) of STS in the age range of above 65 years was higher than other age groups. This finding is comparable to most of the results obtained in previously conducted studies (13,15). On the other hand, Reshadi et al. reported the peak age of incidence between 30-59 years of age (10).

The majority of soft-tissue sarcomas in the Iranian population were detected in the hip and lower extremities [table 4]. As an exception, malignant giant cell STS were more frequent in the upper limbs. The findings in the Iranian population are comparable to the published studies reporting that 75% and 33% of soft-tissue sarcomas of extremities occur in lower limbs and thighs, respectively (10,18).

The present investigation was the first epidemiological study on the soft-tissue sarcoma of the extremities based on Iran National Cancer Registry (INCR) data. Herein, we gathered precious epidemiological findings which can be used in further investigations. Among the notable limitations of the present study, we can refer to incomplete recorded data and a lack of insight into the geographic distribution of tumors in the country. Furthermore, in this registry, due to incomplete histopathology registration of the patients and lack of histology codes, we had no information about histology codes and staging of the lesions. Moreover, no information was available regarding the type of treatment and patient surveillance. The International Classification of Diseases for Oncology, third edition (ICD-03), was used to identify patients with soft tissue sarcomas (2009 to 2014) according to INCR. Although it was better to use the new version of ICD-09 or ICD-10, the data was gathered according to (ICD-03). It is suggested that further studies be conducted to complete the database and analyze this information.

In conclusion, soft-tissue sarcomas of extremities are rare neoplastic lesions. The incidence rate of these tumors in the Iranian population increases with age, and they are more frequent in patients older than 65 years of age; moreover, most of these tumors are more common in males. The three most common histopathological types of soft-tissue sarcomas in extremities include mesenchymal tumor, spindle cell sarcoma and leiomyosarcoma. Among the Iranian population, the majority of soft-tissue sarcomas in extremities occur in the lower limbs and hip region. The three most common soft tissue sarcomas based on (M-codes) in extremities were mesenchymal tumor (M-code: 8800), spindle cell sarcoma (M-code: 8801), and malignant fibrous histiocytoma tumor (M-code: 8800) according to INCR. Most soft tissue sarcomas were detected in the lower limbs and pelvis region.

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