Adrenal myelolipomas composed with adrenal nodular hyperplasia in the same gland

Introduction

Adrenal myelolipoma is a benign tumor, like a lesion composed of an admixture of hemopoietic elements and mature adipose tissue, similar to those seen in the bone marrow. Fewer than 200 cases of adrenal myelolipomas have been reported in the world literature [1].

Adrenal myelolipomas account for about 4% of adrenal incidentalomas [2-5]. Male to female ratio is 1 : 1 [4, 5]. They are usually unilateral but may be bilateral and may also develop in extraadrenal sites like retroperitoneum, thorax and pelvis [5].

To the best of our knowledge, only few cases of myelolipomas mixed with other adrenal or medullary lesions have been reported [6-9]. Myelolipomas have been reported, with or without hormonal activity, as isolated adrenal masses or in association with other adrenal disorders [8, 9]. Adrenal myelolipomas are mainly asymptomatic, only large lesions manifest as abdominal discomfort, bleeding or symptoms of pressing adjacent organs [4, 5, 10, 11].

We present four incidentally found adrenal myelolipomas. Two of them are isolated, asymptomatic, hormonally inactive adrenal myelolipomas, larger than 4 cm, and two cases are combined adrenal myelolipomas and adrenocortical nodular hyperplasia in the same adrenal gland. One of the mixed adrenocortical hyperplasias containing myelolipoma presented hormonal activity. The diagnosis was established by microscopic examination of the specimen.

Case reports

Case 1



A 40-year-old previously healthy woman was admitted to our hospital because of an incidentally found right adrenal mass. She presented abdominal pain of few months’ duration. The computed tomography (CT) scan revealed a right adrenal mass measuring 41 mm × 39 mm × 18 mm. It was described as a large, heterogeneous mass. There were also focal areas with calcification.

The clinical history and laboratory results demonstrated no evidence suggesting that the patient had a metabolic disorder commonly associated with adrenal tumor like hypercortisolism or catecholamine hypersecretion (Table I).

Keeping in view the large size of the adrenal mass lesion, she underwent right laparoscopic adrenalectomy. The postoperative course was uneventful. Histopathological examination revealed adrenal myelolipoma.



Case 2



A 79-year-old female, known to have hypertension, was hospitalized for examinations of a right adrenal mass that was incidentally discovered by abdominal CT during examinations of weakness and liver region pain (suspicion of cholelithiasis).

Blood and urine tests showed that the adrenal mass was non-functional (Table I). The CT revealed a 40 mm× × 36 mm × 25 mm mass arising from the lateral limb of the left adrenal gland consisting of fat. The patient had left laparoscopic adrenalectomy performed. Histopathological examination revealed adrenal myelolipoma.



Case 3



A 56-year-old female with hypertension and diabetes mellitus was found to have an incidental left-side adrenal mass. An ultrasound test was made for urinary frequency. Physical examination revealed hirsutism, pronounced virilization and obesity. She reported irregular menstrual cycles and sterility.

The CT scans revealed solid well-defined adrenal tumor. It measured 2.0 cm × 1.8 cm and caused distortion of the lateral limb of the left adrenal gland.

Laboratory tests showed overproduction of dehydroepiandrosterone sulfate (DHEAS), androstenedione and testosterone (Table I). A 5 days’ 2 mg dexamethasone suppression test was also performed. The plasma testosterone level was not suppressed (it was even increased), thus confirming the diagnosis of hormonal activity of the adrenal tumor. We exclude Cushing’s syndrome using 2 mg and 8 mg dexamethasone suppression test (Table II). Subsequently, the patient had a total adrenalectomy performed. A histological association of adrenal nodular hyperplasia with the focus of myelolipomas was found (Fig. 1, Fig. 2). The androgens’ level was normal after the adrenal mass was removed without any complications.



Case 4



A 66-year-old man was found to have an incidental well-defined echogenic right adrenal mass. The ultrasound test was done because of the right abdominal pain.

The CT scan of the abdomen showed an isolated 70 mm × 5.5 mm × 4.5 mm heterogeneous right suprarenal mass.

The clinical history, physical examination and laboratory tests showed that there was no evidence suggesting that the patient had metabolic disorders commonly associated with adrenal tumor. The patient was subsequently admitted to the hospital for preoperative work-up of the adrenal mass. The endocrine tests did not suggest that the lesion was hypersecretory (Table I).

Because of the adrenal mass size of over 4 cm, the patient underwent laparoscopic adrenalectomy. The postoperative course was uneventful. Histopathological examination revealed myelolipoma mixed with adrenal hyperplasia.

Discussion

Myelolipomas are usually small non-functional tumors. Histologically, the tumor is primarily composed of fatty tissue with scattered hematopoietic elements [1, 5, 10]. Although those tumors are predominantly associated with adrenal glands, the extraadrenal locations are also reported [10]. Moreover, myelolipomas have been reported not only as an isolated adrenal mass, but also in the association with other adrenal pathological conditions, at a frequency of 5-15%, adrenocortical nodular hyperplasia, adrenocortical adenomas or carcinomas, and endocrinological dysfunctions including Addison’s disease, Conn’s syndrome, Cushing’s syndrome, 21-hydroxylase deficiency, 17-hydroxylase deficiency and very rarely, medullary hyperplasia [2, 9, 12-14]. In a group of 294 patients who underwent adrenalectomy, adrenal myelolipomas were found in 4 cases (1.36%). Two cases of myelolipomas coexisted with adrenal nodular hyperplasia.

A group of 408 patients have been followed up in an outpatient clinic for 2-15 years. Radiological and hormonal tests have not revealed the progression of the disease.

Adrenal myelolipomas are usually diagnosed during imaging procedures performed for other purposes and, in the majority of cases, they are incidentalomas. The large lesions have been reported to present with symptoms such as flank pain resulting from tumor bulk, necrosis or spontaneous rupture with retroperitoneal hemorrhage [10, 11]. In our group, the patients were referred because of an adrenal tumor discovered during an ultrasound examination of the abdomen, performed for reasons other than the suspected adrenal lesion. The ultrasound findings were verified by CT in all cases. The first step in diagnosis work-up of adrenal incidentalomas is assessment of their hormonal activity. In a group of four myelolipomas, only one patient with mixed adrenocortical hyperplasia containing myelolipoma, was diagnosed with androgen overproduction.

Most authors recommended surgery for hormonal active adrenal tumors or/and tumors larger than 4 cm resulting from the strong correlation of adrenal tumor size with a risk of malignancy [4, 10, 15]. There are different indications for surgery in myelolipomas. These tumors are benign even when lesions are more than 6 cm; therefore, the tumor size guideline does not apply to myelolipomas [4, 10, 15]. On the CT scans, they are typically seen as a well-circumscribed, heterogeneous suprarenal masses of low density (usually less than –30 HU equivalent to mature fat). Magnetic resonance imaging (MRI) typically shows high signal intensity on T1-weighted images and attenuates with fat suppression [16]. If there are radiological elements of myelolipoma, some authors advocate surgery for tumor size of even more than 10 cm resulting for a risk of developing abdominal pain or life-threatening hemorrhage that may be associated with large tumors [10].

Myelolipomas are usually diagnosed on CT by the pathognomonic presence of fat in the lesion. In our group of four presenting tumors, the CT scans were not suggestive of myelolipomas. We recommend surgery for adrenal incidentalomas larger than 4 cm resulting from a strong correlation of the adrenal tumor size with the risk of malignancy. The subclinical androgen excess may accompany adrenocortical carcinomas [15]. Because of that, in one case we advocated surgery for hormonally active tumor of 2 cm.

The laparoscopic adrenalectomy became the standard of care for the treatment of functioning and non-functioning adrenal tumors. In our own material, two patients underwent laparoscopic adrenalectomy. In case 3, because of suggestion of adrenocortical carcinoma and in case 4, because of the adrenal tumor size of over 7 cm, patients underwent open adrenalectomy.

Mixed changes in adrenocortical tumors are extremely rare. There are only a few cases reported in the English literature [8, 13, 14]. Etiology of mixed adrenal tumors is unclear, although it has been associated with other medical conditions like hypertension, atherosclerosis, diabetes mellitus and other chronic conditions. Various theories of the etiology of associated adrenal nodular hyperplasia or adenoma and myelolipoma had been presented. Myelolipomas are derived from bone marrow embolization or embryonic primitive mesenchymal cells, or arise from metaplastic transformation of adrenal stromal cell [1, 2, 12]. The adrenal gland could be transformed into myelolipomatous elements due to necrotic tissue products, in patients with cancer or other chronic diseases [7]. A case of myelolipoma associated with hyperthyroidism was also reported. The thyroid hormones have important effects on the development, growth, metabolism and tumorigenesis of myelolipoma in the adrenal gland [7]. In our own material, there were no patients with known neoplastic disease and hyperthyroidism.

The hormonal microenvironment might have played an important role in the development of the associated adrenal hyperplasia or adenoma and myelolipomatous foci. Stimulation with adrenocorticotropic hormone (ACTH), cortisol, dehydroepiandrosterone (DHEA) or testosterone might have changed adrenocortical hyperplasia into myelolipomas foci [12, 17]. Similarly, the myelolipomas seen in patients with chronic illnesses, including cancer, may be due in part to prolonged stimulation with ACTH hormone from marked stress [9, 17].

The adrenocortical adenoma or adrenal hyperplasia may have subclinical secretion. The persistent stimulation by hormones might have played a role as a mediator in transforming the adrenal tissue into myeloid cells and fatty replacement [13]. In our own material, the testosterone overproduction could transform adrenal nodular hyperplasia to myelolipomas foci.

In conclusion, adrenal nodular hyperplasia associated with myelolipoma is rare. The mechanism of concurrence remains unclear and multiple factors are probably involved.

References

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Address for correspondence

Anna Babinska MD

Department of Endocrinology and Internal Medicine

Medical University of Gdansk

ul. Dębinki 7

80-288 Gdańsk, Poland

phone: +48 58 349 28 40, +48 58 349 28 41

e-mail: a.mail@wp.pl