LGFMS was identified as a distinct entity in 1987 [
2]. Though patients as young as 3 years and as old as 78 years have been diagnosed with this tumor, it commonly afflicts young to middle aged adults, males more than females [
1,
3-
5].
Dragging of Glisson's capsule due to the large size probably accounts for pain in the present case as these are usually painless slowly growing masses. This mass was mistaken for a hemangioma for reasons cited earlier. Hence a pre-operative cytological diagnosis was not possible. In addition, needle aspiration study is not specific for diagnosis [
6]. This problem of diagnosis was partly circumvented by laparoscopy. The surgical plan was based on the laparoscopic findings and it helped in anatomic localization of the lesion. Further, the identification of large tortuous vessels in the vicinity of the tumor helped in reducing the hemorrhage at surgery. This vascular supply of the tumor accounts for the peripheral enhancement which led us to suspect a possible subcapsular hemangioma of the liver.
LGFMS usually arises in the deep soft tissue of the lower extremity particularly the thigh [
1,
7]. Many of them arise in the skeletal muscle while some of them are confined to subcutaneous tissue [
1]. Although this patient did not show invasion of surrounding tissues on microscopy, these tumors could have extensive infiltration to surrounding tissues even when the tumor is grossly well circumscribed. These tumors have been described in locations like the chest wall, axilla, shoulder, inguinal region, buttock and the neck apart from thigh [
1,
8-
10]. Rare reports include those in the retroperitoneum, the small bowel mesentery, pelvis and the mediastinum [
11-
15]. Though a large LGFMS has been reported to arise from the abdominal wall [
16], it has not been reported in the falciform ligament.
Immunohistochemically, the tumor cells stain strongly and diffusely for vimentin [
1]. Rarely, focal immunoreactivity could be seen for smooth muscle actin, desmin or cytokeratin [
1,
17]. Though CD 34 is negative, one case of diffuse staining has been reported [
18]. LGFMS with giant rosettes has been identified as a separate entity but there are arguments to consider them as same tumor with some varying features on microscopy [
3,
19]. In two LGFMS, no abnormal DNA content or chromosomal aberrations were noted but cytogenetic analysis revealed a ring chromosome in another report [
20,
21]. In the present case, the cells expressed vimentin but there was no immunoreactivity with other markers.
LGFMS must be distinguished from myxofibrosarcoma as their clinical behaviors are different with LGFMS likely to metastasize more often [
22]. The latter lacks areas of fibrous stroma, is uniformly myxoid and in addition it does not show whorled arrangement of tumor cells [
12]. Other malignant tumors that need to be distinguished from LGFMS include malignant peripheral nerve sheath tumor and spindle cell liposarcoma [
1]. More often these lesions are mistaken for benign lesions like myxoid neurofibroma, desmoid fibromatosis, perineuroma or nodular fascitis [
1,
23]. The initial evaluation led us to believe that the tumor was a fibrous histiocytoma. However, with the study of more sections and the help of a reference pathologist, the tumor was diagnosed as LGFMS. The other lesions described above have been excluded in the present case by microscopic findings and immunohistochemistry.
These tumors have been reported to recur and metastasize [
1,
10,
24]. These tumors have recurred as early as 6 months to as late as 50 years in 65% of patients. Metastasis also has been reported to occur frequently with lung being a common site. These tumors have a protracted course even after metastasis. Interestingly, in a larger study, only 5% metastasis has been reported attributing this to prospectively following up a low grade sarcoma while earlier studies have worked back on a metastatic disease [
3]. Although a satisfactory wide excision with an intact capsule was possible, as the tumor was large and deep seated, this patient is kept under follow-up. Patient is recurrence free at one year. Adjuvant radiation was not considered in view of the peculiar position of the tumor. Responses to chemotherapy have been poor and with the limited experience must be considered investigational.
Even with advent of many imaging modalities, in certain situations like the one described, a cytopathological diagnosis may not be technically feasible. Diagnostic laparoscopy would be very useful for anatomic localization. Proper histopathologic evaluation of the tumor and immunohistochemistry is necessary for accurate diagnosis. Exclusion of other similar appearing tumors is essential.
1 AC Ashok,2 and NK Alva3
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