Unique case of metachronous adrenal and hepatic myelolipomas

Abstract

We present a unique case of metachronous adrenal and hepatic myelolipomas in a 62-year-old man. Myelolipomas are most commonly found in the adrenal gland, with extra-adrenal sites such as the lung, retroperitoneum and liver reported. They are a form of benign mesenchymal tumour, with only 25 case reports of a hepatic location published to date. The are no guidelines to its management. Our patient underwent resection due to pain, and after a complicated postoperative period is pain free.

Background

Adrenal myelolipomas are an uncommon form of benign adrenal lipomatous lesion. Hepatic myelolipomas (HM) are exceedingly rare and have only been described in case reports. This is the first report of a patient having metachronous adrenal and HM, both requiring resection.

Case presentation

A 62-year-old man presented with a chronic history of right upper quadrant (RUQ) abdominal pain radiating down his right flank. It was associated with intermittent nausea and vomiting. There was no weight loss. He had a surgical background significant for a previous right adrenalectomy 9 years earlier for a myelolipoma, a laparotomy over 20 years prior for a traumatic liver laceration that did not require resection and open appendicectomy. His medical background included type 2 diabetes mellitus, hypertension and mild developmental delay. The only regular medication was metformin 500 mg three times a day. He had normal vital signs preoperatively, and on examination, he had a soft abdomen with a generally tender RUQ. He underwent investigations as outlined below.

Investigations

The preoperative bloods showed mildly elevated transaminases with alanine aminotransferase (ALT) 114 U/L, aspartate aminotransferase (AST) 54 U/L and gamma-glutamyl transferase (GGT) 91 U/L. Alkaline phosphatase (ALP) and bilirubin was normal, as was creatinine, white cell count and haemoglobin. The patient underwent contrast-enhanced CT and MRI scans which demonstrated a 43×36×25 mm mass in segment VII of the liver (figure 1). On CT, this lesion demonstrated areas of macroscopic fat with peripheral wall calcification, corroborated by the MRI which showed the lesion contained essentially fat, with no infiltration into the surrounding tissue and no enhancement after contrast injection. Based on these features a radiological diagnosis of a possible angiomyolipoma was made.

Figure 1.

Preoperative axial imaging of lesion. (A) Contrast-enhanced CT scan in delayed phase, demonstrating a 43×36×25 mm hypoenhancing heterogeneous lesion demonstrating areas of macroscopic fat, with peripheral calcification in segment VII (solid arrow). (B) Gadolinium MRI scan, T2-weighted, demonstrating a well demarcated, fat containing lesion corresponding to the findings in picture A (dashed arrow).

Treatment

A decision was made for operative management given the patient’s pain without alternative aetiology. The patient underwent an open segment 7 liver resection with cholecystectomy via a reverse L incision. The liver was densely adherent to the diaphragm, and during mobilisation a small partial thickness diaphragmatic defect was oversewn with a 1 nylon suture. There were no other intraoperative complications. The initial postoperative course was complicated by a bile leak, requiring endoscopic retrograde cholangiopancreaticogram and bile duct stenting, and a hospital acquired pneumonia requiring antibiotics and physiotherapy. Histopathology of the resected specimen demonstrated admixed adipose and haemopoietic elements consistent with a myelolipoma, with background liver parenchyma showing steatohepatitis and early cirrhosis (figure 2).

Figure 2.

Microscopic view of resected specimen using H&E staining. (A) ×2 magnification showing liver parenchyma on left (solid arrow) and myelolipoma on right (dashed arrow). (B) x10 magnification showing adipocytes (transparent arrow) and haemopoietic elements such as megakaryocytes (solid arrow).

Outcome and follow-up

The patient was discharged on postoperative day 12. The patient represented 2 weeks later with fevers and RUQ pain and was found to have a right empyema with a subdiaphragmatic collection. The patient underwent a videoscopic assisted decortication where a diaphragmatic defect was noted, and a transdiaphragmatic drain was inserted via the thoracic cavity. This drain remained in situ for long term control of the collection and was retracted slowly over the 2 months following discharge. On most recent follow-up, he was pain free.

Discussion

The authors believe this to be the first reported case of metachronous adrenal and HM in the published literature. Myelolipomas are rare benign tumours of mesenchymal origin that are characterised by mature adipose tissue and haemopoietic elements such as megakaryocytes.^{1 2} The majority of myelolipomas occur in the adrenal gland, and reported extra-adrenal sites include the retroperitoneum, lung and liver.¹ The tumourigenesis of a myelolipoma is largely unknown however hypotheses include metaplastic changes, bone marrow emboli or embryonic remnants of haemopoietic tissue.¹ HMs are rare and described in case reports only. The pathogenesis of an HM is even more unclear than that of an adrenal lesion, with theories including ectopic adrenal tissue, direct invasion and liver cell metaplasia.^3–5 A comprehensive review of HM case reports was recently undertaken by Li et al, who found only 24 existing reports in the literature.⁴ This review found that they are more commonly found in females and in the right liver, with a median age of 56 years. Preoperative imaging included ultrasound, CT and MRI, with angiography used selectively to determine vascular supply. The radiological appearance is dependent on the fat content of the lesion (typically hypodense on CT and hyperintense on T2-weighted MRI), but may contain hyperenhancing parts reflecting haemorrhage, calcification or necrosis.^{6 7} Given the rarity of cases, there are no established guidelines for its management. Percutaneous biopsy has been described as the only reliable way to establish a histological diagnosis preoperatively.⁸ Resection tends to be performed due to symptoms or uncertainty over diagnosis.⁴ In our patient, resection has led to resolution of symptoms despite the high morbidity of the procedure. It is unknown whether or not the patient’s metachronous tumours are due to metastasis from the primary adrenal tumour, direct invasion or a de novo event. Given the patient’s previous trauma, bone marrow emboli are also a possibility.

Learning points.

• Myelolipomas are usually located in the adrenal gland.

• Hepatic myelolipomas are rare and are described in case reports only; this is the first report of a metachronous adrenal and hepatic myelolipoma.

• Histologically they comprise of an admixture of mature adipocytes and and haematopoietic precursor cells such as megakaryocytes.

• Given the rarity, there are no established guidelines to the management of hepatic myelolipomas.