Cholesterol Granuloma of the Abdominal Wall: An Unusual Finding in the Setting of Renal Cell Carcinoma.

Cholesterol granulomas are composed of a distinct type of granulation tissue that contains lipids and cholesterol crystals. They are not believed to be a pathological entity, but rather an inflammatory tissue reaction to the presence of trapped blood secondary to localized hemorrhage.1 Cholesterol granulomas can be identified histologically by the presence of multi-nucleated giant cells, hemosiderin, and red blood cells along with their associated break-down products.1 Recognizing cholesterol granulomas can provide clinical utility as they demonstrate a tendency to mimic carcinoma both clinically and radiologically.

Introduction

Although these complexes are almost exclusively found in the middle ear, petrous apex, and mastoid, there have been isolated reports of their discovery in breast tissue, peritoneum, pancreas, kidneys, and testes. The authors report a case of an incidental discovery of a cholesterol granuloma within the abdominal wall during a partial nephrectomy on a 66 year old female.

Case report

The case reported is a 66 year old female with a BMI of 49.1 kg/m2 and a history of well-controlled hyperlipidemia, hypertension, and type 2 diabetes mellitus, who initially presented with painless gross hematuria for one month. A CT scan of her abdomen revealed a renal mass on the right kidney, measuring 2.9 cm. She had an extensive history of smoking and no family history of genitourinary cancers. Due to the suspiciousness of the mass, she underwent a robotic-assisted laparoscopic right partial nephrectomy. The renal mass was successfully removed and pathology results returned as renal cell carcinoma. During the procedure, a separate 1.3 cm friable mass was noted within the right anterior abdominal wall just below the right sub-costal margin. The mass (Fig. 1) was enucleated from the abdominal wall and sent to pathology. The pathologist's report identified the mass as a cholesterol granuloma (Fig. 2), quite an unusual finding for this location of the body.

Figure 1

Cholesterol granuloma fixed to right anterior abdominal wall.

Figure 2

On higher power, there were numerous cholesterol clefts, admixed with multinucleated giant cells and foamy macrophages, 20× (Hematoxylin & Eosin).

Discussion

Although the cause of this patient's cholesterol granuloma remains ambiguous, there are several etiologies that have been suggested in the literature. Among them, high serum cholesterol levels and trauma have been well-documented. Although our patient's serum cholesterol levels were within normal limits at the time of presentation, she has a history of statin-controlled hyperlipidemia and significant fatty infiltration was seen on her liver during the operation. Despite having a previous cholecystectomy, she reports no history of trauma or other surgeries in her abdomen, likely ruling out hyperlipidemia and trauma as the etiology of her cholesterol granuloma. Interestingly, although clear cell carcinomas contain a very high lipid content, there are no established associations between clear cell carcinomas and cholesterol granulomas in the literature. Therefore, the lipid content of clear cell carcinomas appears to be a coincidence in terms of the formation of this patient's cholesterol granuloma.

Cholesterol granulomas are not thought to have defining imaging features, and this patient's cholesterol granuloma was not seen on computed tomography (even retrospectively). However, this type of lesion may possibly be detected by magnetic resonance imaging, given that cholesterol granulomas appear as high signal intensities on both T1- and T2-weighted images, which can be amplified with intravenous gadolinium. With nearly all cholesterol granulomas representing a benign process, pursuing their identification through imaging does not seem to be of much concern. Since they are known to mimic malignant pathology, diagnoses like lipoma, xanthoma, lipoid granulomatosis, and metastasis must be considered before a lesion is removed and pathologically identified.

In conclusion, although cholesterol granulomas outside the realm of otology are extremely rare, they are generally benign lesions that are easily curable with resection. Early recognition and management is important, as there is a risk that malignancy may be suspected either pre- or intraoperatively and an unnecessarily radical approach may be entertained. It is, therefore, important that both clinicians and pathologists are aware of the possibility for cholesterol granulomas to mimic carcinoma in many places within the body.

Conflict of interest

The authors declare that they have nothing to disclose.