An extremely rare case of synchronous intrathoracic and intra-abdominal tumors.

BACKGROUND

A 42-year-old man was evaluated for general malaise and abdominal fullness in our center. On examination the patient was afebrile, and his physical examination shows flank fullness with mild abdominal tenderness. Laboratory findings were unremarkable; white blood cell count (12300/mm≥), increased proportion of neutrophils on differential analysis (75% neutrophils) and hemoglobin were 14 g/dl. Conventional chest radiograph was done [Figure 1]. Given the patient's history, physical examination, and laboratory findings, abdominal sonography (USG) was also done [Figure 2]. Patient also underwent computed tomography (CT) scan of chest andabdomen and MRI of upper abdomen [Figures 3 and 4].

Figure 1

Conventional chest radiograph shows bilateral lobulated mediastinal masses

Figure 2

(a) Ultrasound abdomen shows right perirenal echogenic masses completely surrounding the kidney (b) left perirenal echogenic masses (c) splenomegaly with multiple variable sized well-defined intrasplenic echogenic mass

Figure 3

(a) Axial contrast-enhanced CT image through mid-thorax shows heterogeneous well-defined bilateral paraspinal masses (*) with a pleural-based mass anteriorly (#) (b) Axial corresponding CT lung window image shows extrapulmonary masses with normal attenuation of lungs (c) Reformatted oblique coronal contrast-enhanced CT image shows well-defined heterogeneous fat attenuating bilateral parvertebral (#), bilateral perirenal (*) and pelvic masses with normal adrenals

Figure 4

(a) Axial T1-weighted and (b) T2-weighted MR image shows masses with heterogeneous signal intensity embedding both kidneys. No evidence of local invasion of kidneys or fascia is seen. Multiple intrasplenic masses are also well seen (c) Axial T2-weighted and (d) and T2-weighted FS MR image shows bilateral perirenal masses (arrows) with heterogeneously intermediate signal and shows suppression of fatty areas on FS sequence

QUESTIONS

What is the radiological finding demonstrated in plain chest radiograph, ultrasound scans, CT and MRI?

What is the diagnosis in this patient?

What are the other important differential diagnoses for the given radiological findings on CT scan and MRI?

ANSWERS

Answer 1

The given chest radiograph shows lobulated bilateral paraspinal masses which does not silhouette the cardiac borders and a pleural-based opacity [Figure 1]. Abdominal sonography (USG) shows perinephric, intrasplenic and presacral echogenic masses [Figure 2]. Contrast-enhanced computed tomography (CT) scan showed multiple fat containing intrathoracic paravertebral and pleural-based masses, bilateral bulky perirenal and presacral pelvic masses. All of them revealed fat attenuating areas (-20 to -94 HU) with interspersed non-fatty soft-tissue densities [Figure 3]. Spleen was also enlarged with multiple intrasplenic hypoattenuating lesions. No lymphadenopathywas noted. Both kidneys were entirely embedded in thefatty masses. Multiple MRI sequences were done to further characterize the masses. Typical fat characteristics were displayed as hyperintense signal on T1 -weighted images and intermediate signal on T2 -weighted images. Fat suppression images demonstrated loss of signal in the fatty components of the lesion. Myeloid elements had low signal intensity on T1 -weighted images and intermediate intensity on T2 -weighted images. Intrasplenic lesions were better demonstrated [Figure 4].

Answer 2

USG-guided fine-needle aspiration and core biopsy of both intrathoracic and perirenalmasses were performed. The core biopsy of masses showedplenty of adipose tissue with interspersed hematopoietic precursors including myeloid, erythroid, and megakaryocyticelements. Several mature plasma cells and occasional hemosiderin-containing macrophages were found. Increased aggregates of lymphoidcells were also found as well. Results were consistentwith the diagnosis of myelolipoma. Bone marrowbiopsy revealed normal cellularity with no evidence of fibrosis, granulomatousinflammation, or cells extrinsic to the marrow.

Answer 3

Appearing as a fat containing soft tissue tumor, the radiological differential diagnoses areliposarcomas, extramedullary hematopoiesis (EHT), lipoma, angiomyolipoma and myolipomas.

DISCUSSION

Myelolipomas, first described in 1905 by Gierke, are rare benign nonfunctional tumors composed of a variablemixture of mature adipose tissue and hematopoietic elements resemblingbone marrow.[1] These lesions most commonly involve the adrenalglands, constituting <4% of adrenal tumors. With improved non-invasive diagnostic imaging in current scenario, incidental discoveryof myelolipomas has become increasingly common.[2] Possibilities include development from embryonic mesenchymal rests in the adrenal gland, hematogenous bone marrow emboli, stress-induced reticuloendothelial cell metaplasia and proliferation of embryonic rests of hematopoietic stem cells.[3]

Myelolipoma are found in wide age range with no sex predilection. Their sizes are also highly variable. Malignant degeneration has not been reported yet.[3] Most of the patients are asymptomatic, local tumor extension or rare occurrence of bulky multifocal masses maylead to non-specific complaints. Imaging findings are quite characteristic. CT shows predominantly low-attenuationareas of adipose tissue with high-attenuationareas of hematopoietic elements. These lesions are well defined with preserved adjoining fat planes. MRI also accurately depicts macroscopic fat using fat saturation technique. Myelolipomas may be discovered incidentally on USG as echogenic masses at various sites but with less accuracy.

Only about 50 cases of extra-adrenal myelolipomas (EAML) are reported in the literature.[4] Their incidence is 0.08-0.4% at autopsy. Thetypical lesion is a solitary, well-defined mass within the abdomen, commonly in the retroperitoneal presacral area (comprising approximatelyhalf of reported cases).[5] Other infrequent sites of involvement includepelvic, perirenal and hepatic regions, with sporadic cases in thoracic, splenic and gastric locations.[4567] In thorax these are usually found as posterior mediastinal masses with very rare occurrence of pleural-based mass.[8] The sizes of EAMLhave been reported to range from 4 to 15 cm, with a mean diameterof 8.2 cm.[9] EAML occurs more commonly in women, with a male: femaleratio of 1:2. The median age at diagnosis is 66.5 yr. A strong association of EAML with underlying inflammatory disorders, diabetes, and cardiovascular disease has been described, similarto that seen with adrenal myelolipomas. Since EAML are histologically identical to their adrenal counterpart, the CT and MR findings appear similar.[3]

The radiological differential diagnoses arementioned above.[3] Specific tissue diagnosis plays the major role and often needed in reaching a final diagnosis. The radiological appearance of liposarcomas depends on its histological type and is usually not well circumscribed. Histologically, well-differentiated liposarcomas are non-hemorrhagic and have lipoblast zones of atypical cellular features.[3] Extramedullary hematopoiesis is a compensatory event in patients with underlying hematological disorder showing marked bone marrow hyperplasia, splenomegaly or other organomegaly and multifocal masses. Unlike extra-adrenal myelolipomas, masses of extramedullary hematopoiesis are usually ill-defined and lack fat.[10] EHT typically demonstrates highercellularity, with universal presence of erythroid hyperplasia, scanty adipose tissue and lack of lymphoid aggregates.[11] Angiomyolipomas are well-defined fat-containing vascular masses that typically arises from the renal cortex, therefore producing a defect in the renal parenchyma. Myelolipomas, on the other hand, have a smooth interface between the cortex and parenchyma that might help in differentiating theselesions. Angiomyolipomas can be differentiated by the lack of megakaryocytes, the presence of thick-walled blood vessels, and scattered spindle cells, which are immunoreactive to HMB-45.[4] Lipomas contain only adipose tissue. No soft tissue seen within them. Myolipomas are very rare and donot contain marrow elements.

Specific therapy of these benign myelolipomas is often not required, as most patients are asymptomatic. Few of the patients which are symptomatic due to local compression require surgical resection. In asymptomatic patients, follow-upwith serial CT scans is appropriate.