Retroperitoneal myelolipoma, a diagnostic dilemma: A case report and review of literature Chauhan K, Garg M, Chaudhry M, Sharma A, Bindal T

CASE REPORT

Year : 2016 | Volume : 5 | Issue : 2 | Page : 90-92

Retroperitoneal myelolipoma, a diagnostic dilemma: A case report and review of literature

Kriti Chauhan, Monika Garg, Manish Chaudhry, Abhimanyu Sharma, Tanupriya Bindal
Department of Pathology, MMIMSR, Ambala, Haryana, India

Date of Web Publication

25-Oct-2016

Correspondence Address:
Manish Chaudhry
Department of Pathology, MMIMSR, Mullana, Ambala - 133 203, Haryana
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/2278-0521.193007

Abstract

Myelolipoma is benign tumors composed of mature adipose tissue and normal hematopoietic elements in variable proportions. It is commonly found in adrenal glands. Extra-adrenal myelolipomas are rare. Their presentation and location can cause them to be easily confused with a malignant tumor. It is difficult to differentiate them from malignant tumors on the clinical and radiological basis alone. Histological examination offers an additional aid in confirming the diagnosis. We report a case of retroperitoneal myelolipoma in a 70-year-old male which was clinically diagnosed as liposarcoma on account of age, location, and imaging.

Keywords: Extra-adrenal, myelolipoma, retroperitoneum

How to cite this article:
Chauhan K, Garg M, Chaudhry M, Sharma A, Bindal T. Retroperitoneal myelolipoma, a diagnostic dilemma: A case report and review of literature. Saudi J Health Sci 2016;5:90-2

How to cite this URL:
Chauhan K, Garg M, Chaudhry M, Sharma A, Bindal T. Retroperitoneal myelolipoma, a diagnostic dilemma: A case report and review of literature. Saudi J Health Sci [serial online] 2016 [cited 2021 Jan 18];5:90-2. Available from: https://www.saudijhealthsci.org/text.asp?2016/5/2/90/193007

Introduction

Myelolipoma is a rare benign tumor consisting histologically of variable proportions of mature adipose tissue and hematopoietic elements. Extra-adrenal myelolipomas (EAML) are uncommon. A little more than fifty cases have been published in the literature in the last two decades. ^[1] We report a case of EAML in the retroperitoneum in a 70-year-old male clinically suspected to be a liposarcoma or angiosarcoma.

Case report

A 70-year-old male patient presented with a complaint of lump in the lower abdomen for 2 months, gradually increasing in size. Lump was not associated with pain, hematuria, vomiting, and fever. On examination, a nontender lump was palpable in the right iliac fossa, hypogastrium, umbilicus, left iliac and left lumbarregion, measuring about 18 cm × 12 cm, having well-defined margins. No organomegaly was noted.

Complete blood counts revealed hemoglobin of 10 g%. Total leukocyte count and platelet count were within normal limits. Biochemical investigations revealed normal liver function test and serum electrolytes; however, renal function tests showed high serum urea levels of 44.96 mg/dl.

Ultrasonography of abdomen showed a large hypoechoic fatty mass across the midline extending from the umbilicus into the pelvis suspicious of a lipoma. Noncontrast computed tomography, and contrast-enhanced computed tomography of whole abdomen showed a large lobulated and septate mass lesion with large areas of fat attenuation and a small area of soft tissue attenuation in the retroperitoneum in the midline extending into the rectal/presacral region measuring 21 cm × 20 cm × 13 cm. No areas of calcification were seen [Figure 1]. A diagnosis of liposarcoma was offered. Based on the above findings, a clinical diagnosis of retroperitoneal liposarcoma was made.

Figure 1: Contrast-enhanced computed tomography of whole abdomen showing a large lobulated mass with areas of fat attenuation in the midline and extending up to the rectum and presacral region

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Ultrasound-guided fine-needle aspiration cytology (FNAC) was performed which yielded a blood mixed fatty aspirate. Smears were made and stained with May-Grünwald Giemsa stain. Smear showed mainly lymphocytes and few neutrophils in the background of adipocytes and abundant red blood cells [Figure 2]. No definite diagnosis could be given on FNAC. Since the radiological findings were suggestive of a liposarcoma, a surgical resection of mass was done. Grossly, the mass was well encapsulated and measured 16 cm × 13 cm × 5 cm. The capsule was intact, shiny and showed scattered hemorrhagic areas. On cutting, the mass showed lobules of fat with interspersed hemorrhagic and gray, tan areas [Figure 3]a. Histological examination showed lobules of adipocytes separated by fibrovascular septa containing hematopoietic elements in the form of megakaryocytes, erythroid, and myeloid precursors [Figure 3]b and c. No atypia, mitosis was seen. Based on these findings, a diagnosis of EAML was made.

Figure 2: Smear showed mainly lymphocytes in the background of adipocytes and abundant red blood cells (MGG, ×40)

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Figure 3: (a) Gross appearance showing a well encapsulated lipomatous mass with gray, tan cut surface, and areas of hemorrhage. (b) Scanner view showing lobules of adipocytes with interspersed hematopoietic elements (H and E, ×40). (c) High power view showing adipocytes and hematopoietic elements in the form of megakaryocytes, erythroid, and myeloid precursors (H and E, ×400)

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Discussion

Myelolipoma is a rare benign and biochemically nonfunctioning tumor composed of the variable amount of fat and myeloid precursors like in normal bone marrow. ^[2] It needs to be differentiated from reactive extramedullary hematopoietic tumors (EMH). ^[3],[4] Patients with EMH tumors are seen in patients of any age and are characterized by anemia, frequent hepatosplenomegaly, and abnormal peripheral smears. In contrast, patients with EAML are usually older than 40 years, have normal blood studies and absent hepatosplenomegaly. In this case, the patient had moderate anemia but no splenomegaly.

Histologically EMH tumors lack circumscription and show predominance of hematopoietic component with erythroid hyperplasia whereas EAML generally have a predominant fatty component and a more conspicuous lymphocytic population. ^[3],[5] The differential diagnoses also include high-grade sarcoma-like well-differentiated liposarcoma, renal angiomyolipoma because of the location and presentation. ^[6],[7] It is essential to be able to differentiate them because of the difference in management. Well differentiated liposarcoma shows lipoblast with atypical cellular features. Angiomyolipoma shows prominent thickened vascular structures and arises from the renal cortex, producing a defect in the renal parenchyma. ^[8] Both lipoblasts and thickened vessels were not seen in our case. Some radiological findings such as size, vascularity, local invasion, and circumscription may contribute to the differential diagnosis. ^[8] Guided FNAC or biopsy offers an adjunct in confirming the diagnosis. ^[5],[9] However, a scant aspirate and the absence of megakaryocytes preclude a definite diagnosis as was in our case too.

The pathogenesis of adrenal myelolipoma remains unclear. Theories include autonomous proliferation of bone marrow cells transferred during embryogenesis, degeneration of epithelial tissue of adrenal cortex and metaplasia of mesenchymal cells. ^[2],[8] Talwalkar et al. have stated that extra-adrenal myelolipoma occurs as a result of activation of dormant hematopoietic stem cells in the retroperitoneum that were active in embryonic life. ^[10] A similar mechanism is likely in our case. An extra-adrenal location of myelolipoma has been reported in mediastinum, presacral region, paravesical space, perirenal area, renal hilum, and pleura. ^{[3],[4],[5],[7],[8],[10]} Surgery is not indicated except in symptomatic patients, size >4 cm, due to rare chances of rupture or if malignancy is suspected.

Conclusion

EAML although rare should always be considered in the differential diagnosis if the lesion is solitary, well circumscribed and fatty on imaging. Guided FNAC or biopsy can be helpful in diagnosing them provided the material is adequate; and hence, prove to be useful in avoiding surgery in asymptomatic patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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