Unusual mucosal lesion: A case of rectal pseudolipomatosis in a 60-year-old patient

Background

Pseudolipomatosis is a very rare pathologic condition initially described by Snover et al. ¹ on colorectal mucosa. At histologic analysis, pseudolipomatosis consists of variable-sized optically empty spaces resembling adipocytes embedded in the lamina propria.^1,2 The frequency of pseudolipomatosis varies around 0.3%–1.7% in endoscopic series; however, the exact incidence of this lesion is difficult to assess because of its rarity and likely its diagnosis is often overlooked by pathologists and endoscopists.^2–4 Colic pseudolipomatosis is often diagnosed incidentally or it is found in patients with gastrointestinal disorders such as diarrhea, constipation, abdominal pain or rectal bleeding.^3,5,6 The pathogenesis of pseudolipomatosis is controversial, it is likely due to gas entrapment in the intestinal wall after mucosal injury by endoscopic procedures.^1,2,5,6 However, cases of pseudolipomatosis have been reported in patients with no history of endoscopy, and it has been postulated that the disease likely resulted from released gas from intestinal intraluminal bacteria.^3,7 Also, cases of gastric pseudolipomatosis have been reported in relation to iatrogenic endoscopic procedures or in connection with Helicobacter pylori infection.^8–10 Due to its rarity, the diagnosis of pseudolipomatosis can be misleading and challenging.^2,4 In order to increase awareness of this uncommon and banal condition, we present herein a case of rectal pseudolipomatosis in a 60-year-old patient presenting with rectal bleeding.

Case presentation

A 60-year-old woman presented with recently discovered mild rectal bleeding. Her medical history was unremarkable and she reported no previous colonoscopy. The physical examination was quite normal with no palpable mass. The patient’s laboratory results were within normal limits. She then underwent colonic endoscopy. Approximately, 25 cm from the anal canal, the colonoscopy revealed diffuse rectal erythematous and superficial ulcerations with areas of normal-looking mucosa (Figure 1, arrows). There were no other abnormal mucosal lesions. Biopsies of the rectal ulcerations were performed. The histologic analysis showed focally ulcerated rectal mucosa recovered by normal epithelium with regular crypts without architectural distorsion. The lamina propria was widely occupied by numerous variable-sized optically empty vacuoles resembling adipocytes (Figure 2). Focally, these vacuoles were fused and form large spaces with discrete amorphous and eosinophilic content (Figure 3, black arrow). The empty vacuoles were intermingled with inflammatory cells and seem to be lined by cells with oval to flattened nuclei (Figure 3, red arrow). These empty vacuoles were extended to the muscularis mucosae. The immunohistochemical analysis showed weak and focal positive staining with CD31 (Figure 4(a)) and S-100 (Figure 4(b)) around the empty spaces (vacuoles), corresponding to reactive inflammatory cells of the lamina propria. Then, the histopathologic diagnosis of rectal pseudolipomatosis was disclosed. After the diagnosis, the patient was lost to follow-up.

OPEN IN VIEWER

Figure 1.

Endoscopic view showing erythematous rectal mucosa (red arrow) with areas of normal-looking mucosa (green arrow).

OPEN IN VIEWER

Figure 2.

The histologic view showing focally ulcerated rectal mucosa recovered by normal epithelium with regular crypts without architectural distorsion. The lamina propria is widely occupied by numerous variable-sized optically empty vacuoles resembling adipocytes. (Hematoxylin-eosin 100×).

OPEN IN VIEWER

Figure 3.

Focally, the vacuoles are fused and form large spaces with discrete amorphous and eosinophilic content (black arrow). The empty vacuoles are intermingled with inflammatory cells and seem to be lined by cells with oval to flattened nuclei (red arrow) (Hematoxylin-eosin 400×).

OPEN IN VIEWER

Figure 4.

Immunohistochemical view showing weak and focal positive staining with CD31 (a) and S-100 (b) around the empty spaces, corresponding to reactive inflammatory cells of the lamina propria. Note the strong CD31 positive staining around vascular spaces in the muscularis mucosae (red arrows) (Immunohistochemistry 50× and 100×, respectively).

Discussion

Pseudolipomatosis is a rare benign condition that may affect many parts of the digestive tract, especially the stomach or the rectocolic portion.^6,8,9 Also, cases of pseudolipomatosis have been reported in the female genital tract, causing challenging diagnostic issues.^11,12 Pseudolipomatosis affects adult patients with no established sex predominance.^1,3,6

Despite the endoscopic and histomorphologic fat-like appearance of pseudolipomatosis, histochemical, immunohistochemical and ultrastructural, studies have proven that this appearance is in fact a result of gas accumulation in the mucosa rather than fat cells.^1,3,6 Many authors have reported evidences showing link between endoscopic procedures and the occurrence of pseudolipomatosis.^6,9,10,13 The chemical mucosal injury leading to gas penetration in the colic mucosa was attributed to disinfectants (hydrogen peroxide or peracetic acid) as pseudolipomatosis appeared in epidemic fashion after using these products for endoscopic desinfection.^5,6 It seems that any injury of any nature (chemical or traumatic) of the mucosa can lead to pseudolipomatosis. Kim and Moon ¹⁰ reported a case of gastric pseudolipomatosis following submucosal injection of normal saline and indigo carmine dye mixed with hyaluronic acid. Our current case had no history of endoscopic procedures and we have no informations about disinfectants used by the endoscopist.

The diagnosis of pseudolipomatosis could be challenging and misleading especially when both endoscopists and pathologists are not aware of it.^2,4,11 The clinical presentation is often asymptomatic or related to associated diseases (diarrhea, constipation and so on). The characteristic endoscopic findings in colic pseudolipomatosis are white or yellow, flat to slightly elevated plaques, phenomenon described as the “snow white sign.”^1,6 However, these characteristic endoscopic patterns may be absent like in our current patient. ⁵

The histopathologic aspect of rectocolic pseudolipomatosis shows typically numerous optically empty spaces resembling adipocytes. These spaces are embedded in the lamina propria and intermingled with inflammatory cells without destruction of glandular structures, and usually the inflammatory cells seem to line the empty spaces suggesting vascular structure or adipocytes.^1,2,4,7 Also, these spaces could have discrete eosinophilic amorphous content. ⁷ We have found focally empty spaces with these eosinophilic content in our current case. However, many lesions could mimic histologic patterns of pseudolipomatosis, such as mucosal lipoma, intestinal lymphangioma or even sclerolipomatosis found in Crohn’s disease.^1,4,14–16 A simple clinical, endoscopic and histopathologic confrontation would lead to the correct diagnosis. Table 1 summarizes some differential diagnoses of rectocolic pseudolipomatosis. At immunohistochemistry, the empty spaces observed in pseudolipomatosis are not truly lined by cells expressing adipocytic markers (like S-100 protein) or vascular markers (CD31, CD34, Factor VIII, D2-40).^1,4,6,7 However, care should be taken not to interpret as falsely positive staining the scattered inflammatory cells that could surround empty spaces and be positive for S-100 or CD31.^4,17,18 In our case, scattered lamina propria inflammatory cells show positive staining with S-100 and CD31, and empty spaces are not truly positive as compared with internal controls (vessels or inflammatory cells). Thus, immunohistochemistry easily rules out the diagnosis of lipoma (negativity of S-100) or the diagnosis of lymphangioma (negativity of vascular immunomarkers). Also, pseudolipomatosis is encountered in adults and has endoscopic patterns different from those of colic lipoma or lymphangioma that usually show elevated masses at colonoscopy.^6,15,16,19

OPEN IN VIEWER

Table 1.

Differential diagnoses of rectocolic pseudolipomatosis.

	Pseudolipomatosis	Lipoma	Lymphangioma
Age
children	–	±	+
adults	+	+	+
Endoscopy	Whitish-yellowish plaques	Elevated mass	Elevated mass
Location
intramucosal	+	±	±
extramucosal	–	+	+
Histology
circumscription	–	+	+
“empty spaces” nature	Gas	Adipocytes	Lymphatics
“empty spaces’’ form	Vaguely uniform	Uniform	Variably-shaped
Immunohistochemistry
S-100	–	+	–
vascular markers	–	–	+

–: usually absent; ±: could be rarely present; +: usually present.

Rectocolic pseudolipomatosis is a benign condition as endoscopic lesions tend to disappear in weeks following initial diagnosis, however, cases associated with pneumatosis intestinalis, subcutaneous and mediastinal emphysema and pneumoperitoneum have been reported.^13,20

Conclusion

Rectocolic pseudolipomatosis is a very rare benign condition with misleading and challenging clinicopathologic presentation. Clinicians and pathologists should be aware of this uncommon lesion for correct diagnosis and appropriate clinical management.