Incidentally detected giant adrenal myelolipoma: A case report

INTRODUCTION

The myelolipoma is a rare, benign neoplasm composed of mature adipocytes and hematopoietic tissue.^[1] Gierke was the first to use the term myelolipoma in 1905 and subsequently by Oberling in 1929, who used the term myelolipoma.^[2] The most common location is retroperitoneum, where mostly adrenal glands are most commonly involved. Initially, it used to be an autopsy finding, but nowadays, with the widespread use of current modern imaging modalities, it is usually diagnosed accidentally on radioimaging. The detection rate of incidental adrenal masses has increased up to 15% with the use of ultrasonography (USG), computed tomography (CT), and magnetic resonance imaging (MRI).^[1] The incidence of adrenal myelolipoma is 0.08–0.2% of all primary tumors of the adrenal glands.^[1]

The adrenal myelolipoma has the same male-to-female occurrence and the most common age group is the 5^th and 6^th decade of life. It is usually involved on the side of gland and non-secreting in nature. Size is commonly smaller than 4 cm.^[3] However, cases of giant secreting adrenal myelolipoma have also been reported.^[4]

CASE REPORT

A 47-year-old male patient presented with pain on the right side of the abdomen. The patient has a history of mild hypertension with no other medical history.

A contrast-enhanced CT scan was done, which showed a suprarenal mass with the possibility of liposarcoma. Surgical resection of the tumor was done and the specimen was sent for histopathological examination. Gross examination [Figure 1] shows capsulated gray-yellow soft tissue pieces measuring 23 × 22 × 13 cm in size and weighing 2.5 kg. Cut section shows a heterogeneous yellowish to grayish cut surface with alternative hemorrhagic areas.

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Figure 1:

Gross examination shows large adipose tissue with hemorrhagic foci.

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Areas of necrosis are also seen. Representative sections are submitted.

Histopathological examination shows well-circumscribed capsulated tumor tissue composed of mature univacuolated adipocytes separated by fibrous septae along with intervening blood vessels and bone marrow elements containing trilineage hematolymphoid cells [Figure 2].

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Figure 2:

Hematopoietic cells mixed with adipose tissue (Hematoxylin and eosin stain 400x). Blue arrow - trilineage hematopeotic cells, double head arrow - fat cells, Blue line - fibrous capsule.

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Foci of hemorrhage are seen with in adipose tissue component. On microscopy, normal adrenal gland tissue was identified compressed as rim at the periphery of myelolipoma confirming its origin from the adrenal gland. No atypical lipoblast or atypical stromal cell is seen. No evidence of malignant neoplasm is seen in the received sections. Thus, the findings are consistent with the diagnosis of myelolipoma of the adrenal gland.

DISCUSSION

Myelolipoma is a rare benign entity composed of fat and myeloid hematopoietic precursor frequently involving the adrenal glands.^[5]

We report a case of adrenal myelolipoma in a 47-year-old patient with a size of 23 cm in the greatest dimension, which is much larger than the usual size of 4 cm. These tumors have been documented to weigh more than 6 kg and to become >40 cm in greatest dimension.^[6] Tumor is usually asymptomatic but can cause flank and abdominal discomfort due to compression of surrounding structures.^[3] Tumor is usually non-functional, although a case of hormone-secreting myelolipoma causing hypertension has been reported.^[4]

Routine imaging modalities, such as USG, CT, and MRI, are all effective in diagnosing adrenal myelolipoma. CT scan is considered sensitive modality for diagnosis of myelolipoma preoperatively.^[3] Differential diagnosis of CT includes liposarcoma, a fat-containing adrenalocortical carcinoma, and adrenal teratoma. Renal angiomyolipoma and retroperitoneal lipoma are among the benign entities of differential diagnosis.^[7] In our case, CT findings were suggestive of liposarcoma with malignant transformation. Surgical resection of tumor was done. Histopathological examination is a must for confirmation of diagnosis. A thorough extensive sampling of tumor tissue should be done. Serial sections were taken at 1 cm apart to rule out any malignant pathology.^[7]

Histologically typical myelolipoma is composed of predominantly mature adipose tissue with no evidence of lipoblast or fetal fat formation.^[5] Adipose tissue is infiltrated by multiple foci of cells of trilineage hematopoiesis.^[3] Areas of hemorrhage and necrosis can be seen, indicating infarction of tumor.^[5]

Myelolipoma, when detected radiologically and not causing any symptoms, usually does not require any treatment. In our case, it was presented as a retroperitoneal mass clinically and diagnosed as liposarcoma radiologically and myelolipoma histopathologically. Hence, giant myelolipoma should be considered a differential diagnosis when evaluating the retroperitoneal mass.

Management and treatment of adrenal myelolipoma should be done as per the patient’s profile. Conservative management can be done if the size of the tumor is <6 cm. Surgery is the mainstay of treatment in symptomatic tumors, rapidly growing tumors, or tumors >6 cm in size.^[1]

CONCLUSION

Incidental myelolipoma when usually diagnosed radiologically and not producing any symptoms does not require any surgical intervention. however, sometims giant myelolipoma can prsent as reteroperitoneal mass and diagnosis can be misdiagnosed as sarcoma on radiology. In such cases, histopathology is important diagnostic modality.