Diagnosis: Endobronchial lipoma

Comment: In retrospect, the CT showed evidence of a low attenuation mass (probably fat) obstructing the bronchus.


Lipomas of lung

Introduction: Tumors classified as lipomas of the lung are rare. Most are endobronchial; parenchymal lipomas are very rare. According to one report (1996), 59 endobronchial lipomas and 3 tracheal ones have been reported [1]. Another report (1989) tallied 109 cases [2]. These tumors show morphologic and genetic features that overlap with pulmonary hamartomas.

Clinical features: Endobronchial lipomas usually occur in men (M:F; 41:7) in the 6th decade, and patients present with cough, hemoptysis, recurrent pneumonia, wheeze, or dyspnea that may have been present for years [1,3] . A few patients are asymptomatic, and the tumor is found on a radiograph or during bronchoscopy for another reason [1]. Most occur in the main or lobar bronchi, and they are rare in the trachea (Table 1) [1,3]. In contrast, 8 parenchymal lipomas have been described [2,4]. Seven of these occurred in men, and the average age was 57. Symptoms included cough, chest pain, and hemoptysis [2].

Table 1: Comparison of Locations of Endobronchial Lipomas vs
All Benign Airway Tumors

Tumor

Number

M/F

Location

Lipomas [1]

62

5.9/1[3]

Trachea 3 (5%);
R Bronchus 23 (37%);
L Bronchus 36 (58%) [1]

Benign endotracheal/endobronchial tumors (see Table 3) [5]

185

3.4/1

Trachea 54 (29%);
R Bronchus 41 (22%);
L Bronchus 53 (29%);
Multiple 37 (20%)

Radiographic changes: The diagnosis of intrabronchial lipoma has been made by CT that shows an intrabronchial lesion of fat attenuation in the range of &endash;80 Houndsfield units [6,7]. Chest radiographs show atelectasis or consolidation of lung distal to the tumor.

Histology: Pulmonary lipomas are circumscribed, benign tumors of mature adipose tissue. They may have a spindle-celled fibrous component. Cellular atypia is almost always absent, but two reports describe rare atypical cells in otherwise benign tumors [8,9]. Bronchial lipomas arise in the mucosa, but may grow between cartilages and have an hourglass shape with a peribronchial component. If the tumor has cartilage, bone, or smooth muscle, it is usually classified as a hamartoma [1]. However, morphologic features of lipoma and hamartoma show some overlap. An endobronchial lipoma described by Som, et al. showed a few small areas of cartilage at the periphery, but no epithelial infolding, as is seen in typical hamartomas [10]. Small amounts of cartilage have also been described in three other endobronchial lipomas [8,11]. Stey, et al. described small foci of bone in an endobronchial lipoma [12]. It should be noted that extrapulmonary lipomas may also show bony or cartilaginous differentiation on occasion [11]. In a study of endobronchial and parenchymal chondroid hamartomas, it was found that endobronchial lesions tended to have more fat and less epithelial infolding than their parenchymal counterparts [13].

Further, the presence of lipoma and hamartoma in the same patient suggests that the two tumors may be related. In one case, a 34-year-old woman had a peripheral chondromatous hamartoma (3.5 cm in diameter) and a predominantly lipomatous tumor (6.5 cm in diamter) with a minor bony, cartilaginous, and epithelial component in the same lobe [9]. In a second case, a 64-year-old man had a lipoma (7 cm) in the middle lobe, a hamartoma in the right upper lobe bronchus, and a 2nd bony hamartoma in the apex of the right upper lobe [14].

Genetics: Recent cytogenetic data have also yielded some evidence supportive of a relationship between lipoma and hamartoma. It was shown in 1991 that the mesenchymal component of one hamartoma had a clonal translocation, but that the epithelial component did not, suggesting that the lesion was a mesenchymal neoplasm [15]. Chromosomal abnormalities that include chromosome 12q14-15 and 6p21 have now been described in many hamartomas, as well as in extrapulmonary lipomas (see table 2) [16-18]. Further, analysis of one pulmonary parenchymal lipoma showed an extra marker chromosome 12 [4]. In addition, molecular rearrangements of the high mobility group I-C gene, which is localized to 12q14-15 or its environs, have been described in both types of tumors even when chromosomal abnormalities have been absent [18,19]. Thus, morphologic and genetic features suggest a close relation between lipomas and hamartomas.

Table 2: Common Chromosomal Abnormalities in Lipomas and Hamartomas

Tumor

Chromosomal abnormalities

Lipoma (N = 68) [16]

12q (N=35)

6p (N=8)

Hamartoma (N = 47) [17,18]

12q (N=19)

6p (N=4)

Differential diagnosis: Types and frequencies of benign tumors seen in a referral center specializing in laser therapy for endobronchial lesions are listed in Table 3 [5].

Table 3: Type and Frequency of Benign Endobronchial Tumors, N = 185 [5]

Type

Frequency

Type

Frequency

Neural--Granular cell myoblastoma

1.6%

Angioma

10.3%

Epithelial--Papilloma (HPV)

28.6%

Chondroma

4.3%

Adenoma

0.5%

Lipoma

3.2%

Mesenchymal--Hamartoma

32.4%

Leiomyoma

2.7%

Amyloidoma

11.4%

Fibroma

2.2%

Schwannoma

2.2%

Treatment: If the diagnosis can be made by biopsy, bronchoscopic removal is recommended if the distal lung parenchyma has not been destroyed by pneumonia and if removal is technically feasible. In one case with symptoms for 15 years, bronchoscopic removal of the tumor cured the symptoms although some radiographic opacities persisted [10]. Over half of the reported tumors were removed via lobectomy or pneumonectomy because of the probability of malignancy [1].

References

1. Yokozaki M, Kodama T, Yokose T, Nishimura M, Yoshida J, Mizokami H, Nagai K. Endobronchial lipoma: a report of three cases. Jpn J Clin Oncol 1996; 26:53-57.

2. Hirata T, Reshad K, Itoi K, Akiyama J. Lipomas of the peripheral lung--a case report and review of the literature. Thorac Cardiovasc Surgeon 1989; 37:385-387.

3. MacArthur C, Cheung D, Spiro S. Endobronchial lipoma: a review with four cases. Br J Dis Chest 1977; 71:93-100.

4. Bridge J, Roberts C, Degenhardt J, Walker C, Lackner R, Linder J. Low-level chromosome 12 amplification in a primary lipoma of the lung. Evidence for a pathogenetic relationship with common adipose tissue tumors. Arch Pathol Lab Med 1998; 122:187-190.

5. Shah H, Garbe L, Nussbaum E, Dumon J-F, Chiodera P, Cavaliere S. Benign tumors of the tracheobronchial tree. Endoscopic characteristics and role of laser resection. Chest 1995; 107:1744-1751.

6. Mendelsohn S, Fagelman D, Zwanger-Mendelsohn S. Endobronchial lipoma demonstrated by CT. Radiology 1983; 148:790.

7. Mata J, Cáceres J, Ferrer J, Gómez E, Castañer F, Velayos A. Endobronchial lipoma: CT diagnosis. J Comput Assist Tomogr 1991; 15:750-751.

8. Matsuba K, Saito T, Ando K, Shirakusa T. Atypical lipoma of the lung. Thorax 1991; 46:685.

9. Palvio D, Egeblad K, Paulsen S. Atypical lipomatous hamartoma of the lung. Virchows Archiv [Pathol Anat] 1985; 405:253-261.

10. Som M, Feuerstein S. Endoscopic removal of lipoma of the bronchus. Report of two cases. Arch Otolaryngol 1951; 54:341-346.

11. Bellin H, Libshitz H, Patchefsky A. Bronchial lipoma. Report of two cases showing chondroitic metaplasia. Arch Path 1971; 92:20-23.

12. Stey C, Vogt P, Russi E. Endobronchial lipomatous hamartoma. A rare cause of bronchial occlusion. Chest 1998; 113:254-255.

13. Tomashefski Jr J. Benign endobronchial mesenchymal tumors. Their relationship to parenchymal pulmonary hamartomas. Am J Surg Pathol 1982; 6:531-540.

14. Jones E, Lucey J, Taylor A. Intrapulmonary lipoma associated with multiple pulmonary hamartomas. Brit J Surg 1973; 60:75-78.

15. Fletcher J, Pinkus G, Weidner N, Morton C. Lineage-restricted clonality in biphasic solid tumors. Am J Pathol 1991; 138:1199-1207.

16. Fletcher C, Akerman M, Dal Cin P, de Wever I, Mandahl N, Mertens F, Mitelman F, et al. Correlation between clinicopathological features and karyotype in lipomatous tumors. A report of 178 cases from the chromosomes and morphology (CHAMP) collaborative study group. Am J Pathol 1996; 148:623-630.

17. Fletcher J, Longtine J, Wallace K, Mentzer S, Sugarbaker D. Cytogenetic and histologic findings in 17 pulmonary chondroid hamartomas: evidence for a pathogenetic relationship with lipomas and leiomyomas. Genes, Chromosomes & Cancer 1995; 12:220-223.

18. Kazmierczak B, Rosigkeit J, Wanschura S, Meyer-Bolte K, Van de Ven W, Kayser K, Krieghoff B, et al. HMGI-C rearrangements as the molecular basis for the majority of pulmonary chondroid hamartomas: a survey of 30 tumors. Oncogene 1996; 12:515-521.

19. Kazmierczak B, Dal Cin P, Wanschura S, Bartnitzke S, Van den Berghe H, Bullerdiek J. Cloning and molecular characterization of part of a new gene fused to HMGIC in mesenchymal tumors. Am J Pathol 1998; 152:431-435.

Clinical summary

Comments: mw6825@itsa.ucsf.edu

Table of Contents

Last revised 10/27/98

Copyright 1998 by Martha L. Warnock. All rights reserved.