Malignant tumors in the liver are predominantly carcinomas, and sarcomas in rare cases. In our report, neither clinical presentation nor radiological examinations revealed the occurrence of a primary tumor elsewhere. This patient had no family or personal history of malignancy either. Unobvious symptoms, non-apparent signs, negative serology tests, near to normal laboratory reports, and untypical radiology appearance misled us to a diagnosis of benign hepatic tumor rather as the MFS of liver.
MFS are classified into two types, solid and “tail-like” pattern by T2-weighted magnetic resonance images (MRI). In “tail-like” type, there are extensive spread along the fascial planes that extended away from the primary site of tumor [20]. MFS with “tail-like” pattern is significantly related to a superficial (subcutaneous) origin, which usually grow in an infiltrative way and have a poor prognosis [21, 22]. However, it should be noted that the solid type appearance of MFS does not necessarily mean negative metastases, as it happened in our patient.
If a biopsy was performed to suggest a diagnosis of MFS, a thorough radiological investigation to estimate the tumor extension should be mandatory. Due to its infiltrative nature, a much wider margin should be applied even for a low or intermediate-grade MFS to prevent a local recurrence [23]. In case of incomplete resection, extra revision surgery should be systematically performed [24]. Unfortunately, initial biopsy was denied in our case and although we removed the tumor with an extended margin, it may be not really adequate as demanded in MFS treatment. In addition, initial pathological findings of the resected liver tumor were not distinct enough to diagnose MFS after the surgery.
In general, low grade MFS is shown as a jelly-like multinodular tumor with a weakly invasive pattern of growth. Under microscope, spindle or stellate-shaped tumor cells are mainly distributed on a mucoid matrix (50%), mainly consists of hyaluronic acid [25]. Extra features include curvilinear elongated blood vessels and occasional existence of pseudolipoblasts. However, no specific findings were identified in our patient, and the existence of bile duct epithelium (CK and CK7 staining in IHC) misled the pathological diagnosis to the benign hamartoma. In fact, it would be very difficult to make the primary diagnosis of liver MFS even with a preoperative biopsy. It was not until the development of extensive peritoneal metastases leading to percutaneous biopsy that MFS was suggested. A thorough microscopic comparison of two pathological specimens Similarities include the presence of plump spindled tumor cells with hyperchromatic nuclei, predominant mucous stroma, and IHC staining of vimentin. However, CK and CK7 staining in the peritoneal specimen were quite different from those in hepatic tumor, may be due to the presence of adjacent liver tissue.
Stringent follow-up was not required in our patient because there was no report of metastasis in hamartoma. In contrast, although low grade MFS is considered to have less potential of malignancy, it shows considerable frequency of metastases (about 20 to 25%) [1, 20]. Metastases of MFS are most common in brain, lung, stomach, small bowel, adrenal gland, pelvis, and retroperitoneum [26]. Larger size (over 5 cm) and necrosis are the most predictors of metastasis [25]. Tumor size, pathological grade, and surgical margins were statistically significant predictors of survival [27]. Primary operation of MFS without careful evaluation and specific plan is the most significant risk factor associated with poor prognosis [28]. From MRI and CT evaluation before the surgery and also according to the intraoperative observation, there is a clear outline of this intrahepatic mass. Therefore we removed the intact mass with a margin approximately 5 mm from the normal liver tissue. More extended margin was not applied and frozen sections were not taken as it was recognized as a benign tumor. In fact, we agree that the surgical margin might be not adequate, should we know in advance that it developed into a malignant manner. A relative wide margin should be always used if the character of the tumor cannot be precisely determined, as long as the surgical conditions allowed.
To our knowledge, this is the first case report of a primary MFS in the liver. Although the occurrence is remarkably rare, we should learn a lesson and bear in mind of this probability. Comprehensive radiological inspection, intensive preoperative evaluation, careful design of operating procedures, wide margin resection, consecutive treatment, and strict periodical follow-ups should be taken to ensure a better prognosis of this kind of neoplastic disease.