Elastofibrolipoma of the colon

To the Editor, During the past several years, we encountered two patients with colon polyps predominantly composed of lipoma‐like adipose tissue elements that were intermingled with characteristic fibrous stroma. Of specific interest were the histological features of the latter, which were identical to those seen in the elastofibromas that occur typically in the subscapular soft tissue. While these features did not align with any of the known diagnostic categories in the gastrointestinal tract pathology, including known variants of lipomas and so‐called ‘elastofibromatous changes/polyps’, they seemed to be morphologically concordant with the ‘elastofibrolipoma’ described by De Nictolis et al. as a mediastinal soft tissue tumor. The two patients were a 65‐year‐old male (Case 1) and a 68‐year‐old female (Case 2). Neither of the patients had prior histories of malignancies nor elastofibromas of the subscapular region. The patient of Case 1 underwent colonoscopy following a positive fecal occult blood test. Colonoscopy revealed a pedunculated polyp in the ascending colon, 35mm in diameter with a long stalk (Figure 1a). Multiple diverticula were also found. The polyp was yellowish with smooth surface, and polypectomy was performed. The patient of Case 2 presented with alternating diarrhea and constipation for several weeks. Colonoscopy revealed a yellowish pedunculated polyp in the transverse colon, 58mm in diameter. Based on the submucosal lipoma‐like appearance of the lesion, polypectomy was performed. Pathologic characteristics of the lesions in both cases were fundamentally the same; therefore, they are described together. The surface of the polyps was covered by normal‐appearing mucosa. The cut surfaces showed homogeneously yellowish, well‐ circumscribed, solid and soft submucosal tumors without areas of hemorrhage or necrosis. Histologically, the submucosal lesions were predominantly composed of nondescript lipoma‐like mature adipose tissue, separated by irregular bands of fibrous connective tissue containing small vessels (Figure 1b). The fibrous tissue was hypocellular and contained numerous elongated or globe‐like eosinophilic to amphophilic deposits which were haphazardly distributed throughout the lesion (Figure 1c). Elastic stains revealed deeply stained and fragmented (i.e., linear, beaded, globular and petaloid) elastic fibers that often had a central dense core and serrated margins (Figure 1d). Bland fibroblast‐like spindle cells and occasional mast cells were also present within the fibrous tissue. These histological features were compatible with “elastofibrolipoma” that was described as a mediastinal soft tissue tumor by De Nictolis et al. No obvious degeneration of the elastic fibers was noted in the vessel's wall or overlying mucosa. An elastofibroma is a rare benign tumor‐like lesion, most commonly observed in elderly people, and predominantly located in the connective tissue between the tip of the scapula and the chest wall. The extensive adipose component in an elastofibroma is an extremely rare feature, and there have been only four reported cases of “elastofibrolipoma” in the literature: one case, which was first defined in 1995 by De Nictolis et al., in the anterior mediastinum and all the other three cases subsequently reported in the subscapular areas. De Nictolis et al. described the “elastofibrolipoma” as having a characteristic fibrous component containing numerous abnormal deposits of elastic fibers, but unlike conventional elastofibromas, the lesion was well circumscribed, surrounded by a fibrous capsule and with more conspicuous adipose tissue centrally and peripherally within the mass. The most common lipomatous tumor in the gastrointestinal tract are lipomas, and colonic lipomas may have variable amounts of additional mesenchymal components. Based on the type of additional tissues present and predominant in the lesion, variants of lipoma have been described such as “angiolipoma”, “angiomyolipoma”, “fibrolipoma” and “angiolipofibroma”. They usually develop as a small, mucosa‐covered intramural polypoid lesions and show fatty masses. Among these lipomatous lesions, the tumor that our two cases most resemble is angiolipofibroma, which is composed of a triphasic mixture of submucosal mature adipose tissue, variably sized vessels and fibrous tissues. However, unlike “elastofibrolipoma” presented here, known variants of lipoma including angiolipofibromas lack abnormal deposits of degenerative elastic fibers in the fibrous stroma.