|Year : 2013 | Volume
| Issue : 2 | Page : 70-75
Histopathological study of soft tissue sarcomas seen in a teaching hospital in Kano, Nigeria
Ibrahim Yusuf1, Aminu Zakari Mohammed1, Yawale Iliyasu2
1 Department of Histopathology, Aminu Kano Teaching Hospital, Kano, Nigeria
2 Department of Pathology, Ahmadu Bello University, Zaria, Nigeria
|Date of Web Publication||7-Dec-2013|
Department of Histopathology, Aminu Kano Teaching Hospital, Kano
Source of Support: None, Conflict of Interest: None
Background and Objective: Malignant soft tissue tumours account for less than 1% of overall human burden of malignant tumours. Increasing incidences of these tumours have been noted worldwide. This study aims to determine the pattern of soft tissue sarcomas seen in a teaching hospital. Materials and Methods: The study comprised of all cases of soft tissue sarcoma diagnosed over a 10-year review from 1 January 1999-31 December 2008. Results: A total of 264 cases of soft tissue sarcomas were reviewed; 162 males and 102 females with a male to female ratio of 1.6:1. The age range was between 3 months and 89 years with a mean age of 39.0 years. Kaposi sarcoma was the predominant histological type with 56 cases (21.2%). This was followed by rhabdomyosarcoma with 54 (20.5%) cases, dermatofibrosarcoma with 52 (19.7%) cases and liposarcoma with 32 (12.0%) cases. The most common site of affectation was the lower limb with 73 (27.7%) cases, followed by the trunk with 66 (25.0%) cases, head and neck with 45 (17.0%) cases and upper limb with 35 (13.3%) cases. Two hundred and eight cases satisfied the criteria for grading, out of which 34.1% were classified in grade I, 32.2% in grade II and 33.7% in grade III.
Conclusion: Soft tissue sarcomas accounted for 8.8% of malignant tumours seen over the review period and Kaposi sarcoma was the predominant histological subtype commonly affecting young adults in our centre.
Keywords: Grading, histopathology, sarcoma, soft tissue
|How to cite this article:|
Yusuf I, Mohammed AZ, Iliyasu Y. Histopathological study of soft tissue sarcomas seen in a teaching hospital in Kano, Nigeria. Niger J Basic Clin Sci 2013;10:70-5
|How to cite this URL:|
Yusuf I, Mohammed AZ, Iliyasu Y. Histopathological study of soft tissue sarcomas seen in a teaching hospital in Kano, Nigeria. Niger J Basic Clin Sci [serial online] 2013 [cited 2023 Feb 4];10:70-5. Available from: https://www.njbcs.net/text.asp?2013/10/2/70/122762
| Introduction|| |
Soft tissue sarcomas are mesenchymal proliferations that occur in the extra-skeletal, non-epithelial tissues of the body, excluding the viscera, coverings of the brain and lymphoreticular system. 
The aetiology of most soft tissue sarcomas is unknown.  They have, however, been associated with urbanisation, overcrowding, toxic fumes and emissions from motor vehicles and industrial machines. Other associations include industrial wastes containing large quantities of polycyclic aromatic hydrocarbons, agricultural and agro-allied chemicals, irradiation, chemicals and heat burns as well as trauma in addition to oncogenic viruses, genetic predispositions and immunosuppression. 
Soft tissue tumours may arise from any location, and occur in all age groups of both sexes with male predominance, though gender and age incidences vary among histological types. The incidence generally increases with age and about 15% arise in children below the age of 15 years. 
Rhabdomyosarcoma is the most common type of soft tissue sarcoma among children and adolescents by a striking majority,  while malignant fibrous histiocytoma (MFH) is the most common in adults. ,
Malignant mesenchymal neoplasms are life threatening and may pose a significant diagnostic and therapeutic challenge to pathologists and oncologists. , Few pathologists have extensive experience with these tumours; hence after biopsy, pathological classification may be incomplete or inaccurate. 
Patients and clinicians fail to appreciate the significance of enlarging soft tissue masses and tissue biopsies for diagnosis are commonly obtained after significant delay. A cursory review revealed an increased registration for soft tissue sarcomas in our department and most of the patients present late with large soft tissue masses.
A significant increase in the understanding of these tumours, both from histopathological and genetic points of view, has led to an upsurge of interest in the study of soft tissue tumours worldwide, with consequent reports of increasing incidences in Europe,  United States,  Asia , and Africa. ,,
| Materials and Methods|| |
The study comprised of all cases of soft tissue sarcomas diagnosed over a 10-year period from 1 January 1999-31 December 2008. Laboratory request forms and duplicate copies of histological reports were retrieved and relevant clinical information and histological type of the tumours were extracted. Corresponding haematoxylin and eosin stained slides were reviewed and evaluated. Phosphotungstic acid haematoxylin (PTAH) stain was used in cases of rhabdomyosarcoma to demonstrate skeletal muscle striations. Thirty (11.4%) selected cases were subjected to immunohistochemistry to determine their unequivocal histological categorisation. Antibodies such as factor VIII-related antigen were used to demonstrate 10 cases of Kaposi sarcoma. Five cases each of fibrosarcoma, malignant peripheral nerve sheath tumour (MPNST), leiomyosarcoma, synovial sarcoma and angiosarcoma were stained with vimentin, S-100 protein, desmin, S-100/CK 7 and factor VIII-related antigen, respectively. The tumours were classified according to the 2005 WHO classification  and graded using the French Federation Nationale des Centres de Lutte Contre le Cancers (FNCLCC)  grading system, which is based on tumour differentiation, mitotic index and tumour necrosis. The results were analysed using frequency tables.
| Results|| |
A total of 2997 malignant tumours of various histological types were diagnosed over the 10-year period. Out of this number, 264 cases were soft tissue sarcomas representing 8.8% of all malignant neoplasm that were diagnosed.
Immunohistochemistry was applied to 30 (11.4%) selected cases. All cases of leiomyosarcoma, angiosarcoma and four cases of fibrosarcoma were positive for desmin, factor VIII-related antigen and vimentin, respectively. A case initially diagnosed as fibrosarcoma showed positivity for S100 protein and CK7 and was re-classified as synovial sarcoma. Only 7 out of 10 cases of Kaposi sarcoma were positive for factor VIII-related antigen. A case of MPNST showed positivity for vimentin and has foci exhibiting herringbone morphology and was re-classified as fibrosarcoma while the remaining were reactive for S-100. The five cases of biphasic synovial sarcoma stained with S-100 and CK 7.
Eight hundred and seventy-four (874) cases of soft tissue neoplasms (benign and malignant) were also received over the same period and soft tissue sarcomas accounted for 30% (264 cases) of the cases. A total of 162 (61.4%) cases occurred in male patients and 102 (38.6%) occurred in females patients giving a male to female ratio of 1.6:1 [Table 1].
|Table 1: Sex distribution of soft tissue sarcoma according to histological subtype|
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The overall age range was from 3 months-89 years with a mean age of 39.0 years. The mean age for males was 42.2 years, which was much higher than that of females (33.1 years). The highest frequency of 54 cases (20.5%) for both sexes occurred in the sixth decade while the lowest frequency of 8 cases (3.0%) occurred in patients older than 70 years of age [Table 2].
|Table 2: Age distribution of soft tissue sarcoma according to histological subtype|
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The lower limb was the most frequently affected site for both sexes with 73 cases (27.7%). This was followed by trunk, head and neck, upper limb, retroperitoneum and perineum accounting for 66 (25.0%), 45 (17.0%), 35 (13.3%), 23 (8.7%) and 22 cases (8.3%), respectively [Table 3].
|Table 3: Site distribution of soft tissue sarcoma according to histological type|
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Kaposi sarcoma was the most common histological type of soft tissue sarcoma in adults accounting for 56 (21.2%) cases. In males, Kaposi sarcoma still remains the most frequently encountered histological type (35 cases, 21.6%) while in females the predominant histological type was rhabdomyosarcoma (26 cases, 25.4%). Embryonal subtype of rhabdomyosarcoma was the most frequent histological type seen in children aged less than 15 years. The frequencies of other soft tissue sarcoma histological types and their sex ratios are shown in [Table 1].
A total of 208 cases of frankly malignant tumours satisfied the criteria for grading, which is based on degree of tumour differentiation, mitotic index and tumour necrosis. Seventy-one (34.1%) cases were classified as grade 1, 67 (32.2%) of the cases as grade 2 and 70 (33.7%) of the cases as grade 3 [Table 4].
| Discussion|| |
Soft tissue sarcomas are reported to be rare in developed nations of United States and Europe and accounts for 0.8-1% of all malignant neoplasms.  There are reports, however, of increasing incidence worldwide.  In Africa, survey of some hospital-based studies show higher proportions than that seen in developed countries.  In conformity with this rise in incidence beyond worldwide figures, studies in Port Harcourt,  Jos  and Ibadan,  Nigeria, found soft tissue sarcomas constituting 2.8%, 11.3% and 2.4% of all malignant solid neoplasms respectively. This study found these tumours representing 8.8% of solid malignancies.
Available literature on soft tissue sarcomas reported a male predominant pattern of affectation. , In this study, the male to female ratio is 1.6:1 and this male predominance agrees with various studies conducted globally. ,,],,
The peak age at which soft tissue sarcomas occur vary among the histological types, but generally the median age is about 60 years. , However, studies mostly from developing countries depicted a lower average age of presentation. In Iran  and Pakistan,  the average age at occurrence is 39.5 and 38.5 years, respectively, and this figure agrees with the findings of this study in which the average age is 39 years.
Approximately, one-third to one-half of all sarcomas of non-osseous origin occurs in the lower limbs , and this predilection for the lower extremities has been clearly demonstrated by several studies in various parts of the world. ,, This review found the lower limbs to be the most common site of occurrence (27.7%) and this agrees with findings in other parts of Nigeria, , Africa , and other parts of the world. ,,
Kaposi sarcoma was the most common histological subtype in adults and accounted for one-fifth (21.2%) of sarcomas received. Even though the serological status of patients in this study was not determined to establish any association between Kaposi sarcoma and human immunodeficiency virus (HIV), the high prevalence of HIV infection estimated to be 3.4% in this locality,  may have resulted in the high frequency of Kaposi sarcoma recorded. Most series reported MFH as the predominant histological subtype of soft tissue sarcoma  However, our finding in this centre is in concordance with that of Mandong et al.,  in Jos where Kaposi sarcoma was also the most frequent histological subtype but differs from reports from Port Harcourt  and Ilorin  where rhabdomyosarcoma and fibrosarcomas predominated, respectively.
Rhabdomyosarcoma is the most common soft tissue sarcoma in children aged under 15 years, adolescents and young adults.  A significant number of rhabdomyosarcoma cases (55.6%) occurred below 15 years of age in this centre with males forming the majority and this is similar to the findings of other local  and international studies. ,, The head and neck remain the most common site of affectation in this and other studies  except reports from Port Harcourt  where the trunk predominated closely followed by head and neck. The histiogenesis of dermatofibrosarcoma protuberans (DFSP) remains controversial; the immunohistochemical profile is more in keeping with fibroblastic rather than fibrohistiocytic or neural derivation.  DFSP constituted about one-fifth (19.5%) of all soft tissue tumours recorded in this study in agreement with Rahaman et al.,  in Ilorin. Available literatures , including this study reported the trunk as the most common site of affectation.
The vast majority of studies found liposarcomas constituting between 10% and 15% of sarcomas of the soft tissue, , with a male predominance and a predilection for the lower limb. ,, This series found them to constitute 12.0% in keeping with the earlier reported findings. However, in contrast to male preponderance recorded in most studies including this, Seleye-Fubara  in Port Harcourt reported adipocytic tumours as being more common in females by a slight margin. They attributed this to the steatopygic nature of women and their tendency to accumulate fat. This, however, cannot be extrapolated to liposarcomas since there is little evidence that lipomas undergo malignant transformation.  The lower limb was the most common location for this tumour in this and several other studies.
Excluding leiomyosarcomas arising from uterine and gastrointestinal origins, which are not included in the definition of soft tissue malignancies, these tumours are said to constitute 5-10% of sarcomas of the soft tissue in conformity with the findings of this study (6.1%). As against female preponderance seen in some other studies,  a significant male bias is depicted in this study and that of Mending et al.,  in Jos. The Jos study  also recorded the thigh as the most common location of leiomyosarcoma while other series including this study found the retroperitoneum to be the most frequent site of affectation. This series found Synovial sarcomas having a mean age of affectation of 28.9 years and majority of the patients being adolescents and young adults. A greater number of males than females were recorded with a predilection for the extremities, particularly the lower limbs. This is in agreement with most other studies. ,,
Fibrosarcoma constituted 4.5% of sarcomas of the soft tissue in this study and this figure agrees with the findings of some local and international studies, , and is at variance with some other studies, ,, which reported fibrosarcomas to be the most common soft tissue sarcoma. Other series , including this study found that a higher proportion of males than females are affected with a predilection for the extremities (41.0%). Among the cases recorded there was a case of infantile fibrosarcoma occurring in a 30-month-old male child. This intermediate grade tumour has a more favourable prognosis than adult fibrosarcomas and instances of spontaneous regression have been documented. , Angiosarcomas are reported to be among the rarest forms of soft tissue neoplasms.  They accounted for 3.4% of sarcomas in this study, which is higher than the frequency of 2.0% reported by Cormier  in United States and 1.5% by Seleye-Fubara in Port Harcourt.  This study and other available literatures ,,, reported a male predominance in its occurrence.
Prognosis of soft tissue sarcoma is dominated by local recurrence and metastasis. Histological grade indicates probability of distant metastasis and overall survival. , The metastasis-free 5 year survival rate was determined in a study by Coindre et al.,  to be significantly lower for grade 3 tumours. In addition, response to adjuvant chemotherapy has been reported to be more efficient in grade 3 tumours due to their high mitotic index.
In this study, there were 32.2% of soft tissue malignancies categorised in grade 2. Grades 1 and 3 constituted 34.1% and 33.7%, respectively. This contrast slightly with the results obtained by Hasegawa et al.,  in their prospective study of prognostic factors of soft tissue sarcomas where they found 25.4% of the tumours to belong to grade 1, 32.6% in grade 2 and 42.0% in grade 3. High grade tumours (grades 2 and 3) constituted 77.2% in their study, which is higher than that recorded by this study (67.8%).
| Conclusion|| |
Soft tissue sarcomas accounted for 8.8% of malignant tumours seen over the review period, which is consistent with relative increase in proportion of these tumours seen in developing countries and Kaposi sarcoma was the predominant histological subtype commonly affecting young adults. Late presentation is a major challenge in our environment and public awareness campaign will help ameliorate this trend. Immunohistochemistry has been invaluable in categorisation of some of these tumours and contributed to ensuring prompt and more accurate diagnosis in our centre.
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[Table 1], [Table 2], [Table 3], [Table 4]