Chondrolipoma of the stomach

Abstract

Chondrolipoma, a rare variant of a lipoma, is a benign mesenchymal neoplasm characterised by mature adipocytes with neoplastic hyaline cartilage formation. We describe the first case of a gastric chondrolipoma. The tumour was completely excised via laparoscopic gastric wedge resection with uneventful postoperative recovery. Histology of the tumour demonstrates mature adipose tissue and benign cartilage with patchy calcification.

Background

Lipomas are benign mesenchymal neoplasms characterised by mature adipocytes. Histologic variants include osteolipoma, myolipoma, myelolipoma, myxolipoma, angiolipoma, fibrolipoma and chondrolipomas.¹ Chondrolipoma is a rare variant of lipoma, containing mature hyaline cartilage among fatty tissue.² A PubMed search of the literature identifies 50 cases of reported chondrolipomas, revealing they can arise from various anatomical sites, with a predilection for the head and neck region (54%), in particular the oral cavity (33%), and the remaining sites include soft tissue (breast 18%, limbs 18%, torso 4%), pelvic cavity (4%), mediastinum (2%) and abdominal cavity (2%). Only one previous case of intra-abdominal chondrolipoma has been reported, arising in the small intestine of a child.³ This is the first case in the literature of a chondrolipoma arising from the stomach.

Case presentation

A 41-year-old Caucasian woman presented with 12 months of abdominal pain. Her medical history was significant for cholecystectomy, caesarean-section, gastro-oesophageal reflux disease and cigarette smoking. Regular medications comprised only esomeprazole. No abnormal findings were noted on examination.

Investigations

Gastroscopy demonstrated a fundal submucosal lesion with approximate diameter of 2 cm and with normal overlying mucosa. Abdominal CT confirmed the presence of a lesion involving and adjacent to the gastric fundus (6.6×5.4×6.8 cm) of predominantly fat density with internal calcific foci (figure 1). Radiologic dimensions were substantially larger than was seen on gastroscopy. The mass appeared to extend into the gastric wall but with a large exophytic component. No evidence of lymphadenopathy or metastatic disease was seen. A gastrointestinal stromal tumour (GIST) variant was the favoured clinical diagnosis, but the radiologic findings were atypical.

Figure 1.

Abdominal CT demonstrates predominantly fatty density mass in relation to gastric fundus with large exophytic component (white arrow). Mass extends into gastric wall with internal calcific foci (red arrow).

Endoscopic ultrasound (EUS) demonstrated a circumscribed hyperechoic lesion external to the anterior fundal gastric wall, with a smooth border separate from the preserved muscularis propria. The EUS features were suggestive of a lipoma. Nonetheless, the atypical calcification within the lesion raised concern and laparoscopic excision of the lesion was considered as the best course of treatment.

Macroscopic examination of the excised lesion demonstrated a well-circumscribed 7.0×5.5×3.0 cm mushroom-like exophytic homogenous fatty lump, completely covered by a thin smooth translucent membrane. It extended from a small base in the submucosa and was broadly exophytic on the serosal surface, excised clear of excision margins (figure 2A, B). The overlying gastric mucosa was intact with no evidence of ulceration, inflammation, Helicobacter organisms, intestinal metaplasia, dysplasia or malignancy.

Figure 2.

(A, B) Gross appearance of extramural lipomatous tumour. (C) Close inspection shows cartilaginous islands within the tumour.

The tumour comprised mature adipocytes admixed with multiple islands of benign hyalinised cartilage, within which dystrophic calcification was noted (figure 2C). No nuclear atypia, hyperchromasia, mitotic figures or necrosis were present (figure 3A, B). These features were consistent with the diagnosis of chondrolipoma of the stomach.

Figure 3.

(A) Microscopic: benign cartilage circumscribed from mature adipocytes in the tumour external to stomach wall. (B) Microscopic: the cartilaginous component shows sparse normal chondrocytes singly distributed in lacunae in a chondromyxoid matrix.

Differential diagnosis

The gastric mural-based location favoured GIST as the main differential diagnosis. GISTs account for 80% of gastrointestinal tract neoplasms and most frequently originate in the stomach.⁴ Nonetheless, radiologic and EUS features typical for GIST were absent. GISTs appear on CT as soft tissue density lesions. There may be haemorrhage or necrosis as they outgrow their vascular supply, hence they are typically peripherally enhancing with non-enhancing areas of central necrosis. Calcification is uncommon (3%).⁵ Simple lipomas present on CT as well-defined, homogenous fat-density lesions (−70 to −120 HU) without solid components.⁶ The degree of gastrointestinal wall involvement is valuable in distinguishing subepithelial lesions and can be reliably assessed with EUS. GISTs are visualised as hypoechoic lesions arising from the muscularis propria, whereas lipomatous lesions are hyperechoic and typically confined to the submucosa.⁷

In consideration of the fatty appearance on CT and EUS, differentials expanded to include lipoma and lipoma variants such as fibrolipoma, angiolipoma, myolipoma, spindle cell lipoma, chondroid lipoma, chondrolipoma and osteolipoma. The lesion had none of the features of haemorrhage, haemosiderin or fat necrosis, which may be seen in reactive metaplastic change after regional trauma.

Treatment

The patient underwent a gastroscopy followed by a laparoscopic gastric wedge resection. At laparoscopy, a 6 cm lipomatous lesion was found at the fundus of the stomach. A wedge resection was performed, divided ends stapled and specimen extracted.

Outcome and follow-up

Postoperative recovery was unremarkable. The patient was discharged home on day 2 on a soft-diet and a regular proton pump inhibitor.

Discussion

Lipomas are benign mesenchymal tumours composed predominantly of adipocytes. Lipomatous lesions are uncommon within the gastrointestinal tract and when seen are most frequent in the colon (60%–75%). Gastric lipomas are rare and account for <5% of gastrointestinal lipomas and <1% of gastric neoplasms. Rarely, they may prolapse, cause obstruction and intussusception. Patients may present with pain, dyspepsia, bleeding and ulceration, due to irritation and recurrent intussusception.⁵

Lipomas may have mesenchymal components such as cartilage, blood vessels or bone.¹ Chondrolipoma is a rare histologic variant of lipoma. A gastric chondrolipoma has never been previously described. This may have relevance if atypical imaging findings are noted on assessment of submucosal gastric lesions. Only one other case of chondrolipoma has been reported within the abdomen or gastrointestinal tract, in which a jejunal chondrolipoma caused small intestine obstruction in an 11-year-old boy. No definitive lesion could be visualised on imaging and the jejunal lesion was only discovered during surgery.³ This contrasts with our gastric chondrolipoma’s clear radiologic features. Interestingly, both jejunal and gastric chondrolipomas had exophytic components and incorporated multiple layers of gut wall, from submucosa to subserosa and serosa, respectively. This diverges from conventional gastrointestinal lipomas that are characteristically confined to submucosa and rarely subserosa.⁸ Gastric lipomas tend to be located in the antrum.⁹ This chondrolipoma exceptionally arose from the fundus of the stomach.

Two theories predominate on the pathogenesis of chondrolipoma. One is that cartilage arises from chondro-osseous metaplasia secondary to chronic mechanical stress or trophic disturbance.^{3 10} This change may occur with the tumour being in proximity to bone, a large joint, lipodystrophic change or a myxoid background.¹¹ While this theory examines the periarticular nature of cartilage formed under biomechanically stressed sites, visceral sites of chondrolipomas (mediastinal, intra-abdominal, pelvic) invites further investigation. The second theory is that cartilage may originate from multipotent cells in the mesenchymoma.³ Nakano et al showed differences in the expression of transforming growth factors TGF-β1, -β2, -β3, bone morphogenetic protein and latent TGF-β binding protein-1 between the metaplastic cartilage in chondrolipoma compared with that of native cartilage from the trachea and in osteochondromas, which is suggestive of variable pathways in chondrogenesis in various cartilage-containing lesions.¹²

Despite having similar radiological appearances and a similar name, the non-adipocytic component in chondroid lipomas lack hyalinised (true) cartilage and instead comprise non-hyalinised chondromyxoid matrix with round cells and occasionally show haemorrhage and fibrosis. Chondroid lipomas also share the same t(11;16) translocation seen in hibernomas, which is not found in chondrolipomas.¹³ `

The treatment of choice for chondrolipoma is surgical excision; this enables definitive diagnosis and exclusion of more sinister differential diagnosis. Extrapolation from the literature suggests that recurrence is rare, and no metastatic potential has been reported.^{3 10}

Learning points.

• Chondrolipoma is a benign, rare, histologic variant of the more prevalent classic lipoma. This is the first case described of a chondrolipoma of the stomach.

• Diagnosis of chondrolipomas require clinical, radiological and pathological correlation.

• Complete surgical excision is diagnostic and likely to be curative.