Background

Synovial sarcomas are malignant neoplasms with mesenchymal and variable epithelial differentiation. They are infrequent, accounting for 5-10% of all soft tissue sarcomas [1]. For every one million people in the United States, one to two are diagnosed with synovial sarcoma each year [2]. This tumor is most common in adolescents and young adults; with the majority of cases occurring between 10 and 40 years of age [1, 3]. It is rarely encountered in those over 50 years old. There is a slight male preponderance [3], and similar incidences in all ethnic groups have been described [4, 5]. This neoplasm can occur in almost any location in the body. In the vast majority of cases, it involves deep soft tissue of the lower extremities, frequently in the vicinity of large joints, like the knee and ankle [6]. It can also occur in viscera (heart, lung, pleura, kidney), oral cavity, mediastinum, retroperitoneum, peritoneum, central nervous system, and peripheral nerves. Typically, it has a slow growth pattern and benign radiologic appearance. Clinically, synovial sarcomas can be associated with pain depending on their location in relation to nerves. Some authors have observed that long-lasting pain at the tumor site before the development of swelling is more common with synovial sarcomas than with other sarcomas [7]. Most cases, however, are diagnosed only when their size is larger than 5 cm [8]. Similar to other soft tissue sarcomas, synovial sarcomas in the hand-wrist area are infrequent [9].

This paper documents an unusual case of hand-wrist synovial sarcoma in a 69-year-old Caucasian woman, and characterizes this condition’s demographic, pathologic, and clinical features with a literature review.

Case presentation

A 69-year-old Caucasian woman with a past medical history of low back pain, hypertension, and hyperlipidemia presented with a chief complaint of a dorsal ulnar-sided left hand-wrist mass that had been growing slowly over the previous 10 years. The patient stated that the mass had become progressively more painful over time, being particularly tender when she wore a watch. There had been no history of preceding trauma nor constitutional symptoms. On physical exam, the skin on the hands and wrist was intact with normal musculature. In the left dorsal ulnar wrist, near the extensor carpi ulnaris tendon, there was a small palpable mass that was semi-firm and not mobile; quite tender to palpation. A hand-wrist X-ray showed marked osteoarthritic changes. An initial clinical diagnosis of a probable ganglion cyst was made, and the patient underwent surgical excision of the mass.

The pathology of the soft tissue fragments revealed a biphasic neoplasm composed of spindle cells admixed with neoplastic glands (Fig. 1). No necrosis or active mitotic activity was seen. The tumor cells were positive for TLE1, focally positive for CK19, CK7, and S100, and negative for CDX2, SMA, CK20, and TTF-1 (Fig. 2). Due to tissue fragmentation, surgical margins could not be assessed; although they appeared to be involved by the neoplasm. FISH (fluorescence in situ hybridization) for SS18 (SYT) gene break-apart rearrangement on chromosome 18q11.2 was performed (Fig. 3), and the SYT gene rearrangement was detected in 71% of cells; thus confirming the diagnosis of synovial sarcoma.

Fig. 1
figure 1

a Hematoxylin and eosin (H&E) stain, magnification ×10: low-power view of the neoplasm. b H&E stain, magnification ×40: high-power view of the epithelial component surrounded by fascicles of spindle cells. c H&E stain, magnification ×40: high-power view of bundles of spindle cells. d H&E stain, magnification ×40: thickened bundles of wiry collagen (arrows)

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Fig. 2
figure 2

a–c CK7 (a), CK19 (b), and TLE1 (c) stains, magnification ×20: strong expression of CK7 and CK19 in the epithelial component, with focal/patchy expression in the spindled cells. The tumor cells are positive for TLE1

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Fig. 3
figure 3

Interphase FISH for the assessment of SS18 (SYT) gene break-apart rearrangement: the first probe, a SpectrumOrange labeled ~ 650 kb probe, extends distally from the SS18 (SYT) gene. The second probe, a SpectrumGreen labeled ~ 1040 kb probe, lies proximal to the SS18 (SYT) gene. In normal cells that lack SS18 (SYT) gene rearrangement, two pairs of orange and green fusion signals will be observed. In abnormal or tumor cells with SS18 (SYT) gene break-apart, one fusion, one green and one orange signal pattern are seen, as in the cells showed

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CT (computed tomography) of the thorax/abdomen and pelvis were without evidence of metastatic sarcoma. The tumor was classified as AJCC (American Joint Commission on Cancer) Stage IIA. A wide re-excision of the tumor was performed with en-bloc resection of the distal ulna. The resected tissue showed an ill-defined 1.0 × 0.5 × 0.5 cm firm mass involving the soft tissue without involving the bone. The histopathologic exam confirmed the prior diagnosis. The patient received adjuvant radiotherapy and had regular follow-ups for 5.5 years with no evidence of any local recurrence of the tumor or distant metastases. The timeline of the episode of care is summarized in Fig. 4.

Fig. 4
figure 4

Timeline of the episode of care

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Discussion and conclusions

Synovial sarcomas are rarely encountered in routine clinical practice. Nevertheless, they are a highly malignant type of soft tissue sarcoma. Therefore, clinicians and pathologists should always maintain a high level of suspicion to ensure these cases are not unrecognized.

Synovial sarcomas in the hand-wrist area are an uncommon occurrence. Their frequency is 4-8.5% of all synovial sarcomas in different studies [10,11,12]. When a synovial sarcoma arises in the hand-wrist, the incidence of finger involvement is less common than that of the carpus [4, 13]. Clinically, many of these tumors, particularly when small in size, are initially misinterpreted as benign lesions such as ganglion cysts or glomus tumors.

The synovial sarcoma case herein described is particularly unusual considering the patient’s age and sex (a woman in her late sixties), and the infrequent location (the hand-wrist region). Despite its name, synovial sarcomas do not arise from synovium and rarely occur in the joints. A microscopic similarity to the primitive synovium was observed early in the literature, but its histogenesis is still unclear [6, 14]. Nevertheless, the term synovial sarcoma continues to be used. A 2010 study suggested that a human multipotent mesenchymal stem cell may be the cell of origin [15].

Histologically, there are three variants of synovial sarcoma [16]: monophasic, biphasic, and poorly differentiated. The monophasic variant is characterized by fascicles of atypical spindled cells with scant cytoplasm and monotonous vesicular nuclei, often overlapping. There is a variable mitotic rate. Collagenous stroma can be more or less abundant, and thickened bundles of “wiry collagen” can be seen. Vasculature can be prominent, and hyalinization or myxoid changes are rarely seen. Mast cells are frequently observed, and necrosis is uncommon. Biphasic synovial sarcoma contains the aforementioned spindle cells, and in addition there is an epithelial component showing glandular or nested growth. The epithelial cells have amphophilic cytoplasm and round to ovoid nuclei. The glandular lumina may contain eosinophilic amorphous material or mucin. Rarely, squamous metaplasia can be seen. Poorly differentiated synovial sarcoma is characterized by hypercellularity, hyperchromatic nuclei, polymorphism, and increased mitoses. Necrosis is common. Poorly differentiated areas may be present adjacent to more typical monophasic or biphasic areas. In some cases, the entire tumor is poorly differentiated.

A characteristic cytogenetic translocation t(X;18) (p11.2;q11.2) is present in almost all synovial sarcomas; helping provide diagnostic confirmation. This translocation fuses SS18 (SYT) in chromosome 18 and SSX1, SSX2, or SSX4 in chromosome X [17]. Immunohistochemistry shows that synovial sarcomas are strongly positive for TLE1, although other sarcomas and carcinomas can rarely express TLE-1 [18, 19]. Keratins and EMA are diffusely positive in the epithelial components, and focally positive in the spindled cells [20]. Focal S100 protein or SOX10 positivity can also be seen in a percentage of cases. CD56 and CD99 are usually positive, while CD34, SMA, desmin, myogenin, PAX3, synaptophysin, TTF-1, and NKX2 are negative [21].

In 1986, Dreyfuss et al. [11] performed a literature review of hand synovial sarcoma cases occurring between 1934 and 1984. An English literature search in PubMed using the terms “synovial sarcoma”, “hand” and “wrist” from 1983 to 2020 was performed to provide a review of cases not included in the aforementioned review. Our literature search started from 1983 in order to include a paper from 1983 (Kinsella et al. [22]), which was not reported in Dreyfuss’s review. One hundred and eighty-nine cases of synovial sarcoma of the hand-wrist have been recorded [6, 8, 10, 12, 13, 22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67] during the past 37 years (Table 1). Among these, 57 cases in the hand-wrist where demographic, pathologic, and clinical information was available were analyzed (Table 2).

Table 1 Summary of the Pub-Med English literature on 189 cases of synovial sarcoma of hand-wrist (1983–2020)
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Table 2 57 cases of synovial sarcoma of the hand-wrist in the Pub-Med English literature (1983–2020): demographic, pathologic, clinical, and therapeutic features are reported for each case
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The demographic features of the cases reported in the literature are summarized in Table 3. The male-to-female ratio was 1.23:1, which is slightly diminished compared to Dreyfuss’s ratio (1.68:1). The mean age of the present literature review (33.6 years) is similar to that from Dreyfuss’s study (33 years). Thirty-seven subjects (65%) were between 10 and 40 years old, and only 5 (8.7%) were above 69 years old. These results are in accordance with the findings of Dreyfuss et al. and in keeping with the literature [16]. Therefore, these findings corroborate that the case report presented herein is a rare occurrence.

Table 3 Summary of demographic, histologic and clinical parameters for the 57 subjects analyzed. For each parameter, N highlights the number of subjects for whom the parameter was provided
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The hand was the most commonly involved location (45 cases, 78%). Nearly all cases involved the soft tissue with the palmar surface of the hand reported in 18 cases, the dorsal surface in four, the area between metacarpals in five, the fingers in eight, the anatomical snuffbox in one. A digital nerve was involved in one case, while an unspecified hand area was reported in eight cases. The wrist was involved in 14 cases (24.5%), and two cases concomitantly involved the hand. Among these, in 13 cases affected the soft tissue, while only one case involved the median nerve. These findings confirm that the incidence of finger involvement by this type of sarcoma is less common than that of the carpus [13].

In 20 cases collected, the duration of symptoms before diagnosis was clearly stated in the studies and is reported in Table 3. In six cases, the tumors were initially considered benign conditions, like abscesses, fibromas, arthritis, and so forth. According to most authors, a delay in diagnosing this kind of tumor is very frequent due to the insidious growth pattern and non-specific radiological appearance. These tumors can be present for extended periods (2–20 years). In the case report herein described, the patient presented with a slowly growing hand-wrist mass, which became progressively more painful over a 10-year period.

The greatest dimensions of the tumors at diagnosis were clearly reported in only 34 cases. Size ranged between 0.5 and 10 cm, with an average of 2.8 cm. In eight additional cases, the size reported was “5 cm or less”, while in two it was “more than 5 cm”. In total, 37 cases out of 44 were diagnosed when the tumor size was 5 cm or less. Therefore, this review and the presented case report show that in a majority of cases, this tumor is 5 cm or less in greatest dimension. This is in disagreement with few articles stating that larger tumor sizes are usually present at diagnosis [13]. The rates of different histologic subtypes are reported in Table 3.

Radical surgical excision was the treatment of choice (57 cases, 100%). Adjuvant radiotherapy was performed in 29 cases (51%), while chemotherapy was used in 12 cases (21%), either before or after surgery. These percentages are higher than those observed by Dreyfuss et al., who found that 30% of patients had radiotherapy and 5% chemotherapy. This demonstrates more widespread use of therapies like radiation and chemotherapy in recent decades to treat synovial sarcomas.

The follow-up period is summarized in Table 3. The recurrence rate was 32.6% (16 out of 49 followed-up cases): in 4 cases local recurrences were seen, in 9 cases lung metastases, in one case lymph node metastasis, and in 4 the site of recurrence was not specified. According to the literature, the rate of recurrence of these tumors is around 80% [60]. In Dreyfuss at al. review, the rate of recurrence was 54%. Several factors have been associated with a higher recurrence risk: advanced age, larger tumor size (> 5 cm), central location, male sex, neurovascular or bone invasion, p53 overexpression, high proliferative index, specific SYT-SSX fusion types, and incomplete excision [68, 69]. Regarding the excision of hand-wrist tumors, it has to be considered that these body areas present particular challenges due to their specific anatomic features: there is limited soft tissue, and each compartment is small. Therefore, it can be difficult to obtain wide surgical margins [70]. In the present literature review, chi-square analysis was used to compare the rate of recurrence and metastasis in different subgroups of patients. The rate of recurrence and metastasis was not significantly different (p > 0.05) when comparing tumor size (less than or equal to 5 cm versus those greater than 5 cm), histology subtype (biphasic versus monophasic), and age (those less than or equal to 40 versus those older than 40). It is uncertain why the recurrence rate in the present literature review is relatively lower compared to the review by Dreyfuss et al. and also considering that Dreyfuss did not provide the tumors’ size at diagnosis in their analysis.

In the literature analyzed, the mortality rate was 10.2% (5 out of the 49 followed-up subjects). Sixteen patients (28%) survived at least 5 years after beginning treatment. Twelve (21%) survived at least 10 years, with one surviving more than 32 years. The overall five-year survival rate for synovial sarcomas of any location is 27–85% in the literature [13, 16]. Dreyfuss et al. in their review focused on hand synovial sarcomas found that 18% of the patients survived five years after beginning treatment and 9% survived ten years. Therefore, the present literature review showed an improved 5-year and 10-year survival in hand-wrist sarcomas in the recent decades. Various factors seem to have a poor survival prognostic value in subjects affected by synovial sarcomas [71]: advanced age at diagnosis, tumors larger than 4 or 5 cm, central location, poorly differentiated histology. Recent data suggest that fusion type does not have survival prognostic value. The synovial sarcoma in the case report herein described had several favorable prognostic factors that could justify the uneventful five-years follow-up: peripheral location, small size, lack of poorly differentiated histology, negative resection margins at the re-excision.

In conclusion, this literature review confirms that synovial sarcomas of hand-wrist are more frequent among males and subjects 10 to 40 years old. These findings corroborate that the case report presented is a rare occurrence. In the literature analyzed, the incidence of finger involvement by this type of sarcoma was less common than that of the remaining areas of the hand and wrist. A delay in diagnosis was not common, probably because a high level of suspicion for this tumor has been achieved. Moreover, in most cases, this tumor was diagnosed when 5 cm or less in greatest dimension. The five-year survival rate in the cases analyzed was higher than that reported in the previous literature review on hand synovial sarcomas; suggesting an improved survival in the recent decades.