CASE REPORTS

Refer to: Shaub M, Gordonson J, Sargent EN: Extrapleurallipoma. West J Med 124:147-149, Feb 1976

Extrapleural Lipoma

MICHAEL SHAUB, MDJAY GORDONSON, MDE. NICHOLAS SARGENT, MDLos Angeles

LIPOMAS ARE THE most common type of primarybenign neoplasm of the soft tissues of the chestwall. Intrathoracic lipomas are quite rare and areusually found in the mediastinum.1 2 Extrapleurallipomas are even more uncommon, and the pur-pose of this report is to present four cases oflipomas in the extrapleural space.

Reports of CasesCASE 1. The patient was a 48-year-old asymp-

tomatic Mexican-American man. On a routineradiograph of the chest a typical extrapleural massmeasuring 2 by 5 cm, with a convex medial bor-From the Department of Radiology, Los Angeles County/Uni-

versity of Southern California Medical Center, Los Angeles.Submitted, revised, July 8, 1975Reprint requests to: Michael Shaub, MD, Box 717, Los Angeles

County/USC Medical Center, 1200 North State Street, Los An-geles, CA 90033.

der and tapering margins, was seen in the rightupper posterior thorax (Figure 1). There wereno associated rib erosions. At thoracotomy, afatty extrapleural mass was found which taperedas it entered the intercostal space. Exploration ofthe intercostal space proved the mass to be en-tirely within the thoracic cavity. Following totalremoval 6f the lipoma, the patient had an un-eventful postoperative course.

CASE 2. The patient was a 33-year-old asymp-tomatic Caucasian woman. On a routine radio-graph of the chest a mass measuring approxi-mately 5 cm with a convex lateral border over-lying the cardiac shadow, we., noted located in theright anterior cardiophrenic area (Figure 2). Thepreoperative diagnosis was a pericardial cyst, butat thoracotomy a large lipoma measuring approxi-mately 10 by 15 cm was found. It projected in-feriorly from the eighth intercostal space in themidline near the anterior attachment of the dia-phragm and it was freely movable upon the peri-cardial surface. The postoperative course wasuneventful.

CASE 3. The patient was a 31-year-old asymp-tomatic black man. Findings on a routine radio-graph of the chest showed a typical extrapleuralmass measuring 2 by 5 cm, smoothly outlinedwith a convex medial border and tapering mar-gins, located in the anterior portion of the leftposterior thorax (Figure 3). There were no riberosions. Diagnosis of this lesion was made byneedle aspiration biopsy which yielded typical

Figure 1.-(Case 1) Left, posteroanterior radiograph of

the chest showing a 2 by 5 cm extrapleural mass within

the right upper thoracic cage. Right, right anterior

oblique view showing extrapleural characteristics, that

is. tapering margins and smooth convex border, best

seen in profile in the right upper posterior hemithorax.

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CASE REPORTS

fatty tissue cells. The patient refused a thora-cotomy and the lesion did not change in sizeduring a recent 13-month follow-up.

CASE 4. The patient was a 58-year-old blackwoman with a left breast mass. Findings onroutine radiograph of the chest again showed a

typical extrapleural mass measuring approxi-mately 3 by 4 cm, smoothly outlined, with a con-vex medial border and tapered margins, locatedin the right upper posterior thorax. There was noevidence of any rib erosion (Figure 4). On leftradical mastectomy for the breast mass, adeno-

Figure 2.-(Case 2) Left, posteroanterior radiograph ofthe chest showing a 5 cm extrapleural mass overlyingthe right cardiac border. Right, lateral view of the chestshowing location in the anterior portion of the medi-astinum.

Figure 3.-(Case 3) Posteroanterior radiograph of thechest showing a 2 by 5 cm extrapleural mass withsmooth border and tapering margins in the left hemi-thorax.

Figure 4.-(Case 4) Right anterior oblique view show-ing typical tapering margins of an extrapleural masslocated in the right posterior hemithorax.

148 FEBRUARY 1976 * 124 * 2

CASE REPORTS

carcinoma was seen. Needle aspiration biopsy ofthe extrapleural mass showed it to contain fattytissue cells. Thoracotomy was refused and therewas no change following a recent observationafter 17 months.

DiscussionThoracic lipomas have been classified into three

groups.46In the first group, an intrathoracic and extra-

thoracic element is connected by a narrowedisthmus of tissue. This usually extends throughan intercostal space, but in rare instances thetumor may extend through a defect in the ster-num. These transmural tumors have been calledthe "hourglass" or "dumbbell" types.

In the second group, a tumor originating in themediastinum extends up into the neck. This iscalled the cervicomediastinal type, with part ofthe tumor in the upper mediastinum and part inthe base of the neck. Occasionally, tumors in theanterior-superior mediastinum may originate inthe thymus gland where they are called thymo-lipomas.

In the third group, the tumor is entirely intra-thoracic and this is called a subpleural lipoma.It may occur in a costal diaphragmatic locationor mediastinal location. They are more frequentwithin the mediastinum and of the 61 cases ofpurely intrathoracic lipomas reported by Seltzer,46 cases were exclusively mediastinal.

Pathologically, intrathoracic lipomas are similarto lipomas in other locations. They are composedof lobules of normal adult fat, with or without acapsule.6 Most patients with intrathoracic lipomasare asymptomatic7 and the tumors are discoveredon routine roentgenograms of the chest. Intra-thoracic lipomas generally vary in size from 3 to10 cm.6 Occasionally, they may become verymassive, for instance Leopold reported a case inwhich a lipoma weighed 17.5 pounds.8 They havebeen reported in patients ranging in age from 11months to 72 years.6'9The possibility of an intrathoracic lipoma

should be considered in the differential radio-graphic diagnosis of any extrapleural mass. Whenthe tumor occurs in a mediastinal or subcostallocation, it will have the characteristic appearanceof an extrapleural lesion with the followingradiographic features. The margin will be smoothand sharply convex, usually with tapering edgesforming an obtuse angle. There is usually no evi-dence of rib erosion or destructive osseous

changes. The fatty nature is not readily apparentwhen it is contrasted with the lung parenchymathat it displaces. However, when the tumor is ofthe "hourglass" type, the fatty nature may beapparent when contrasted with the water densityof the adjacent soft tissues of the chest wall. Inthis type of tumor, rib erosions may be present." 9If the extrathoracic component is clinically pal-pable, this aids in the diagnosis of the lesion.

Gramiak and Koerner'0 reported two cases ofsubpleural lipoma in which the shape of thelesion changed during respiration. Heuer3 de-scribed a peripheral radiolucency in a largemediastinal mass which proved to be a lipomaand he felt that the margin of the lipoma wasmore radiolucent than the rest of the tumor.Seltzer6 added the observation that the entiretumor, because of its high fat content, may appearless radiopaque than other solid tumors of equalsize. These signs were not helpful in the pre-operative diagnosis of the four cases presented.

In the differential diagnosis other extrapleurallesions to be considered include metastatic neo-plasms. These are actually the most commoncause of extrapleural masses and are usually as-sociated with destructive rib changes. Extrapleuralhematomas may also present similar radiographicfeatures, but the clinical history of trauma andassociated rib fractures will aid in differentialdiagnosis. Neurogenic tumors and fibromas andmesotheliomas may be indistinguishable radio-graphically.

SummaryFour cases of extrapleural lipoma are presented

and the radiographic characteristics are discussed.Two cases were diagnosed by needle aspirationbiopsy and two cases were diagnosed followingopen thoracotomy.

REFERENCES1. Ten Eyck EA: Subpleural lipoma. Radiology 74:295-297,

19602. Keeley JL. Vana AJ: Lipomas of the mediastinun-1940-

1955. Surg Gynec Obstet 193:313-322, 19563. Heuer GJ: The thoracic lipomas. Ann Surg 98:901-919, 19334. Bigelow NN, Ehler AA: Lipothymoma-Unusual benign

tumor of the thymus gland. J Thoracic Surg 23:528-538, May 19525. Falor WH, Ferro FE: Lipothymoma. Surgery 39:291-296, Feb

19566. Seltzer RA: Subpleural lipoma. J Lancet 84:100-102, Mar

19647. Krause LF, Ross A: Intrathoracic lipomas-A report of

three cases and review of the literature. Arch Surg 84:444-448,Apr 1962

8. Leopold RS: A case of massive lipoma of the mediastinum.Arch Intern Med 26:274-278, 1920

9. Shawker TN, Nilprabhassorn P, Dennis JM: Benign intra-thoracic lipoma with rib erosion in an infant. Radiology 104:111-112, Jul 1972

10. Gramiak R, Koerner HJ: A Roentgen diagnostic observa-tion in subpleural lipoma. Am J Roentgenol Radium Ther NuclMed 98:465-467, Oct 1966

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