Two Case Reports of Adrenal Myelolipoma: Insights into a Rare and Benign Mass

Abstract

Introduction

Adrenal myelolipoma (AML) is a rare, benign, and nonfunctional tumor composed of adipose and hematopoietic tissue. With the increasing use of imaging techniques, AML is more frequently detected as an incidental finding. While small and asymptomatic cases are managed conservatively, larger tumors or symptomatic cases often require surgical intervention, with laparoscopic adrenalectomy emerging as a preferred minimally invasive approach.

Case Presentation

This report presents two cases of AML diagnosed in a single day at our institution. The first case involved a 53-year-old male with persistent abdominal pain, while the second case was a 61-year-old male with an incidental adrenal mass discovered during imaging for an unrelated procedure. Both patients successfully underwent laparoscopic adrenalectomy, and histopathological analysis confirmed the diagnosis of AML. No postoperative complications were observed, and follow-up showed favorable outcomes.

Conclusion

AML remains a clinically significant entity due to its varied presentation and potential complications. While traditionally open adrenalectomy was the standard, laparoscopic adrenalectomy is a safe and effective alternative, even for larger tumors, providing benefits such as reduced morbidity. Further research is needed to refine management strategies and long-term outcomes for AML patients.

Introduction

Adrenal myelolipoma (AML) is a benign, nonfunctional, and rare neoplasm consisting of mature adipose and hematopoietic tissue in varying proportions [1]. It is primarily localized in the adrenal glands within the retroperitoneal space and was historically discovered post-mortem. Historically, AML was most commonly identified incidentally during autopsy or cadaveric dissection before the widespread use of advanced imaging modalities. Such findings highlighted its often asymptomatic nature and benign biological behavior. Narayan et al. [2] reported an incidental AML discovered during cadaveric dissection that mimicked ectopic adrenal or renal tissue, underscoring the diagnostic challenges posed by fat-containing retroperitoneal lesions in the absence of imaging correlation. These early anatomical observations contributed to the foundational understanding of AML before the modern era of radiologic diagnosis. However, with the increased use of advanced imaging techniques like ultrasonography, computed tomography (CT), and magnetic resonance imaging, it is now frequently detected incidentally, accounting for approximately 6%–16% of adrenal incidentalomas [3]. Although AMLs are predominantly asymptomatic, larger tumors may lead to abdominal or flank pain due to compression of adjacent structures and, in rare cases, can be associated with hemorrhage or rupture [3]. Histopathological examination plays a crucial role in the diagnosis of masses and tumors [4, 5]. Imaging studies are essential for the diagnosis of AML, with CT and MRI being the most reliable methods, though histopathological examination remains the gold standard for definitive diagnosis [6]. While open adrenalectomy has been the traditional treatment for large AMLs, recent advancements have demonstrated the feasibility of minimally invasive laparoscopic resection, offering a promising alternative for selected cases [7]. This report presents two cases of AML which was observed in 1 day at our institution during the adrenalectomy.

Case Presentation

A 53-year-old male presented with a 2-month history of continuous abdominal pain. He denied experiencing headaches, respiratory symptoms, nausea, vomiting, changes in bowel habits, fever, jaundice, hematemesis, or melena. His physical examination was unremarkable, and his vital signs were within normal limits. The patient’s body mass index was 35 kg/m². He reported no history of medication use and had previously undergone an appendectomy operation. Routine biochemical tests, including electrolytes and ionized calcium, were within normal ranges. Blood urea was measured at 45 mg/dL (reference range: 18–55 mg/dL), and serum creatinine was 1 mg/dL (reference range: 0.5–1.4 mg/dL). Hormonal assays, including follicle-stimulating hormone (3.75 mIU/mL; ref: 0.95–11.95 mIU/mL), luteinizing hormone (2.21 mIU/mL; ref: 0.57–12.07 mIU/mL), prolactin (12.98 ng/mL; ref: 1.46–19.4 ng/mL), testosterone (17.29 nmol/L; ref: 4.41–35.38 nmol/L), progesterone (<0.1 ng/mL; ref: <0.1 ng/mL), morning cortisol (8.3 µg/dL; ref: 3.7–19.4 µg/dL), thyroid-stimulating hormone (0.88 mIU/L; ref: 0.35–5.55 mIU/L), and hemoglobin A1C (5.5%; ref: <5.7%) were all within normal limits. Abdominal and pelvic ultrasound revealed a well-defined hyperechoic lesion measuring 70 × 90 mm, located in the subcapsular region of the posterior segment of the right liver lobe. A subsequent abdominal CT scan demonstrated a lobulated, well-circumscribed retroperitoneal mass situated above the right kidney. The mass exhibited heterogeneous density with areas of soft tissue attenuation and measured 73 × 56 mm in axial dimensions. The lesion contained macroscopic fat with attenuation values consistent with adipose tissue (approximately −30 to −100 Hounsfield units), interspersed with areas of soft tissue density corresponding to myeloid components. No evidence of local invasion was observed. Following contrast administration, mild enhancement of the nonfatty elements was noted without suspicious washout characteristics. MRI findings were consistent with those observed on CT. On MRI, the lesion demonstrated high signal intensity on T1-weighted images with signal suppression on fat-saturated sequences, confirming the presence of macroscopic fat. T2-weighted images showed heterogeneous signal intensity corresponding to the mixed adipose and hematopoietic composition. The patient underwent transperitoneal laparoscopic adrenalectomy using 4 ports. After mobilization of the surrounding structures, the adrenal mass was carefully dissected with preservation of the tumor pseudocapsule and without evidence of capsular rupture or spillage. The specimen was placed in an endoscopic retrieval bag (endobag) and extracted through a slightly enlarged port site to prevent tumor fragmentation. Intraoperatively, a retroperitoneal mass was identified without evidence of renal vascular compromise. The excised specimen measured 70 × 50 × 30 mm (Fig. 1a). Histopathological examination confirmed the diagnosis of AML (Fig. 1b, c). At 3 months of follow-up, the patient remained asymptomatic, with no evidence of postoperative complications, hormonal abnormalities, or radiologic recurrence.

Fig. 1.

Macroscopic and microscopic features of 2 cases of AML: macroscopic view of the first case of AML (a); hematoxylin and eosin (H&E) staining of the first case of AML(10×) (b); H&E staining of the first case of AML (×40) (c); macroscopic view of the second case of AML (d); H&E staining of the second case of AML (×10) (e); H&E staining of the second case of AML (×40) (f).

A 61-year-old man presented with no clinical symptoms but revealed a right adrenal mass in a CT scan. A CT scan performed before percutaneous nephrolithotomy revealed a 103 × 54 mm well-defined right adrenal mass containing substantial macroscopic fat with negative attenuation values consistent with adipose tissue. The lesion showed heterogeneous internal architecture without invasive features, consistent with a giant AML based on its maximal diameter exceeding 10 cm. His physical examination was unremarkable. He had good general condition and stable vital signs. The patient’s body mass index was 34 kg/m². He reported no history of medication use. Routine biochemical tests, including electrolytes and ionized calcium, were within normal ranges. Blood urea was measured at 39 mg/dL (reference range: 18–55 mg/dL), and serum creatinine was 1.2 mg/dL (reference range: 0.5–1.4 mg/dL). Hormonal assays, including follicle-stimulating hormone (3.25 mIU/mL; ref: 0.95–11.95 mIU/mL), luteinizing hormone (1.8 mIU/mL; ref: 0.57–12.07 mIU/mL), prolactin (7.24 ng/mL; ref: 1.46–19.4 ng/mL), testosterone (11.11 nmol/L; ref: 4.41–35.38 nmol/L), progesterone (<0.1 ng/mL; ref: <0.1 ng/mL), morning cortisol (5.7 µg/dL; ref: 3.7–19.4 µg/dL), and thyroid-stimulating hormone (2.31 mIU/L; ref: 0.35–5.55 mIU/L), were all within normal limits. Although hemoglobin A1C (5.9%; ref: <5.7%) was remarkable. The patient underwent transperitoneal laparoscopic adrenalectomy using a four-port technique. The mass was dissected meticulously with intact pseudocapsule preservation. No intraoperative rupture or tumor spillage occurred. The specimen was retrieved using an endoscopic specimen retrieval bag through a protected extraction site. Intraoperatively, a retroperitoneal mass was identified without evidence of renal vascular compromise. The excised specimen measured 100 × 50 × 30 mm (Fig. 1d). Histopathological examination confirmed the diagnosis of AML (Fig. 1e, f). At 6 months of follow-up, the patient remained clinically stable without evidence of recurrence, endocrine dysfunction, or postoperative complications.

Discussion and Conclusion

AML remains a subject of clinical interest due to its benign nature, varied presentation, and evolving management strategies. While traditionally considered an incidental finding, the increasing use of high-resolution imaging has led to a higher detection rate, even in asymptomatic individuals [7, 8]. However, the optimal management of AML, particularly in cases of large tumors, remains debated. The two cases in this report illustrate different clinical scenarios: 1 patient presented with persistent abdominal pain, while the other had an incidental discovery during imaging for an unrelated condition. A key challenge in AML management is determining when surgical intervention is necessary. Literature suggests that tumors larger than 6 cm, symptomatic cases, or those with imaging characteristics suspicious of malignancy should be considered for adrenalectomy [8, 9]. While traditional open adrenalectomy was historically preferred for large AMLs, recent studies advocate for laparoscopic approaches even for tumors exceeding 10 cm (giant AML), citing reduced morbidity and faster recovery [8]. Both cases in this report underwent laparoscopic adrenalectomy, which is becoming a widely accepted approach due to its minimally invasive nature and reduced recovery time. One of the critical concerns with AML is its potential for complications such as spontaneous hemorrhage, rupture, or mass effect on adjacent organs [7, 9]. While rare, tumor rupture has been reported, particularly in lesions greater than 10 cm, raising the question of whether elective surgery should be considered preemptively in large asymptomatic AMLs [9]. The literature suggests that hemorrhagic changes occur in up to 19% of cases, with rupture observed in approximately 4.5%, reinforcing the rationale for surgical excision in larger tumors [8]. In the present report, neither patient experienced rupture, but their tumor sizes (7.3 cm and 10.3 cm) placed them within the range where surveillance alone may pose risks. Although the gross pathological examination described areas of disruption, this was attributed to specimen handling and sectioning during pathological processing rather than intraoperative rupture. Histopathological examination remains the gold standard for diagnosing AML, allowing differentiation between benign and malignant tumors [10, 11]. In both cases, postoperative histopathological analysis confirmed AML without signs of malignancy, highlighting the importance of definitive tissue diagnosis [12]. Furthermore, while AMLs are typically nonfunctioning, a subset may exhibit hormone production, necessitating biochemical assessment in certain cases [9]. The cases in this report had normal hormonal profiles, aligning with the majority of AML presentations.

The differential diagnosis of AML includes retroperitoneal liposarcoma, renal angiomyolipoma, and ectopic adrenal tissue. Retroperitoneal liposarcoma may present as a large fat-containing mass; however, it typically demonstrates infiltrative margins, thick septations, nodular nonfatty components, and, histologically, cytologic atypia and lipoblasts, which are absent in AML. Renal angiomyolipoma, another fat-containing lesion, is usually renal in origin and characterized by a triad of dysmorphic blood vessels, smooth muscle cells, and adipose tissue; radiologic continuity with the renal cortex helps differentiate it from adrenal lesions. Ectopic adrenal tissue may mimic adrenal masses but lacks the characteristic admixture of mature adipocytes and trilineage hematopoietic elements seen in AML [13]. Careful radiologic assessment combined with definitive histopathologic evaluation allows accurate distinction between these entities and prevents misdiagnosis. On CT scan, AML typically appears as a well-circumscribed adrenal mass containing macroscopic fat, with attenuation values ranging from −30 to −120 Hounsfield units. The presence of intermixed myeloid elements may produce heterogeneous soft tissue density areas within the lesion. After contrast administration, AML generally demonstrates mild to moderate enhancement of the nonfatty components without aggressive washout patterns [3, 14]. On MRI, the fatty component shows high signal intensity on T1-weighted images with signal suppression on fat-saturated sequences, while T2-weighted images demonstrate variable heterogeneous signal depending on the proportion of hematopoietic tissue. These characteristic imaging features often allow a confident preoperative diagnosis of AML and help differentiate it from other adrenal or retroperitoneal masses [3, 14]. Histopathological examination remains the gold standard for confirming AML and excluding malignant mimickers. In both cases, microscopic evaluation demonstrated mature adipocytes admixed with trilineage hematopoietic elements, including erythroid, myeloid, and megakaryocytic precursors. Importantly, there was no evidence of cytologic atypia, lipoblast formation, increased mitotic activity, tumor necrosis, or infiltrative growth pattern. These findings effectively excluded retroperitoneal liposarcoma, which typically exhibits atypical stromal cells and lipoblasts, as well as other malignant fat-containing neoplasms. The absence of aggressive histologic features correlated with the patients’ uneventful postoperative recovery and lack of recurrence during follow-up, further supporting the benign biological behavior of AML. During follow-up (3 and 6 months, respectively), neither patient demonstrated recurrence or endocrine abnormalities, supporting the favorable short-term outcomes of laparoscopic adrenalectomy for AML, including in giant lesions.

Despite its benign nature, optimal management of AML remains debated. While surgical intervention for tumors larger than 6 cm is due to increased risk of hemorrhage, others suggest that lesions exceeding 8–10 cm, often termed “giant AML,” may carry a higher probability of spontaneous rupture and therefore warrant elective resection. However, robust prospective data defining a universal surgical threshold are lacking. Conservative management may be appropriate for small, asymptomatic AMLs, but surveillance carries potential risks, including interval growth, hemorrhagic transformation, and rare rupture. Additionally, long-term outcome data comparing observation versus early surgical intervention remain limited. Our cases, including one giant AML measuring 10.3 cm, support the feasibility and safety of laparoscopic adrenalectomy even for larger tumors, while underscoring the need for clearer evidence-based guidelines regarding size-based management strategies. The 2 cases discussed highlight the diverse presentation of AML, 1 with symptoms of abdominal pain and the other discovered during imaging for an unrelated issue. Although both lesions were clinically nonfunctioning and baseline biochemical tests and baseline morning cortisol levels were within normal ranges, we acknowledge that comprehensive endocrine evaluation of adrenal incidentalomas typically includes overnight dexamethasone suppression testing and measurement of plasma free or urinary fractionated metanephrines and normetanephrines. These investigations were not fully performed in our cases, which represents a limitation of this report. However, neither patient demonstrated clinical signs or perioperative features suggestive of functional adrenal pathology. Management of AML, particularly in large tumors, remains a topic of debate, but minimally invasive laparoscopic adrenalectomy has become an effective treatment, offering benefits such as reduced morbidity and quicker recovery. Histopathological examination remains crucial in confirming the diagnosis and ruling out malignancy. While most AMLs are nonfunctional and asymptomatic, close monitoring or surgical intervention may be warranted for larger tumors or those with concerning features, as evidenced by the patients in this report. Future studies should focus on refining guidelines for AML management, including the long-term outcomes of conservative surveillance versus early surgical intervention.

Statement of Ethics

Ethical approval was waived for this case report by local guidelines. The patients permitted us to use clinical information and photographs for publication by written consent. Written informed consent was obtained from the patients. A CARE checklist is provided in the online supplementary file (for all online suppl. material, see https://doi.org/10.1159/000551367) for reporting case reports.

Conflict of Interest Statement

The authors confirm that there are no known conflicts of interest.

Funding Sources

There was no significant financial support for this work.

Author Contributions

M.S. and M.J.N. contributed to conceptualizing the study and finalizing the manuscript. S.S., A.A., A.K., and H.Y. gathered the data and contributed to the writing of the initial draft.

Funding Statement

There was no significant financial support for this work.

Data Availability Statement

The data that support the findings of this study are not publicly available due to privacy reasons but are available from the corresponding author upon reasonable request.