Gastric liposarcoma was first reported in 1941 by Abrama and Tuberville (7). Since then, a limited number of cases have been reported with an annual incidence of 50 to 60 new cases (8). More than 80 subtypes have been described and this wide diversity is due to continuous advances in molecular diagnosis (3). Liposarcoma is the most frequent histological subtype of soft tissue sarcomas, accounting for 50% and 25% of retroperitoneal and extremity sarcomas, respectively (6, 9). In histological terms, liposarcomas are divided into 5 subtypes: well-differentiated, myxoid, pleomorphic, mixed-pleomorphic, and dedifferentiated (3). Well-differentiated liposarcoma (WDLPS) or atypical lipomatous tumor (ALP), is a locally aggressive neoplasm that occurs during the fourth to fifth decade of life. This pathology represents approximately 40–45% of all liposarcomas and is composed of an atypical proliferation of adipocytes and focal nuclear atypia in both, adipocytes and stromal cells (3). The mixed subtype is the second most prevalent liposarcoma in adults and frequently occurs in children and adolescents. It presents a myxoid stroma and similarly, round to ovoid cells with a minimum of lipoblasts (4). Less than 5% of liposarcomas are of the pleomorphic type, this subtype exhibits a variable number of pleomorphic lipoblasts and denotes a high-grade sarcoma (10). Usually, dedifferentiated liposarcoma originates from recurrent WDLPS. A transition from an atypical lipomatous tumor to a non-lipogenic high-grade sarcoma is evident in this pathology and, like WDLPS, immunopositivity for CDK4 and MDM2 is used for diagnostic support, although is not confirmatory (11).
Approximately, 30% of gastric liposarcomas are located in the antrum, especially in the lesser curvature, followed by the gastric fundus, body, and esophagogastric junction (5). Symptoms are closely related to the tumor size. In small tumors (≤ 4cm), as in the present case, the symptoms are nonspecific, such as diarrhea, abdominal pain, and weight loss (12). Larger (> 4cm) tumors can present symptoms related to gastrointestinal bleeding, particularly those that graze against the contralateral gastric wall and subsequently ulcerate. Although our patient did not present any symptoms, it could have been complicated by an endoluminal obstruction in the pylorus due to the size and location (4).
EGD presents well-defined, yellowish, submucosal masses that share similar characteristics to gastric lipomas. Likewise, lipomas show typical endoscopic signs such as naked fat, tending, cushion, or pillow sign (13, 14). It is important to mention that our patient presented the pillow or cushion sign even though it is a malignant tumor, which implies that this finding is not exclusive to lipomas (15). Computed tomography (CT) allows us to assess the tumor characteristics as well as the possibility of metastatic disease. WDLPS presents as heterogeneous masses with fatty density and is associated with enhanced areas (16). However, the mixed subtype is related to cystic areas and enhancement in solid components. Furthermore, the finding of hemorrhagic areas and necrosis suggests dedifferentiated liposarcoma (17).
Despite the negative result in the immunohistochemical study for MDM2, our patient's histological diagnosis was WDLPS. This finding is in line with previous studies that support the use of MDM2 and CDK4 only as supplemental studies (12, 18). The differential diagnoses of gastric liposarcoma are multiplied, which include gastrointestinal stromal tumors (GISTs), gastric lymphomas, and retroperitoneal liposarcomas (19, 20). In the case of WDLPS, the main differential diagnosis is gastric lipoma since its endoscopic and tomographic characteristics are similar. Given this likeness, conservative surgery should be attempted due to the possibility of benignity.
A complete surgical resection achieving free margins is related to a better prognosis without requiring lymphadenectomy (21). However, most studies report radical surgeries in which the preservation of healthy parenchyma is scarce, even in small tumors (≤ 4cm) (5). Only 43 cases have been reported in the English literature, including 40 patients who received radical surgery (standard gastrectomy). The type of surgery was not described in two patients, and only one treated with endoscopic submucosal dissection (ESD) achieved free surgical margins (22, 23). The surgical technique that we present allowed us to completely resect the tumor preserving the gastric parenchyma and achieving free surgical margins with greater safety than endoscopic procedures.
Herein, we report a patient with a large gastric liposarcoma with a complex location successfully treated with minimally invasive surgery and achieving preservation of gastric parenchyma. Despite the difficult tumor position, from our perspective, this surgical approach was safe and will allow a better quality of life compared to radical surgery.