原文題目

原文題目(出處)： Sialolipoma of minor salivary glands. Annals Diag Pathol 2011;15:6-11

原文作者姓名： Cassiano Francisco Weege Nonaka, Karuza Maria Alves Pereira, Pedro Paulo de Andrade Santos, Roseana de Almeida Freitas, Márcia Cristina da Costa Miguel

通訊作者學校： Federal University of Rio Grande do Norte, Natal, RN, Brazil

報告者姓名(組別)： 黃靜瑜 intern J 組

報告日期： 100/06/13

內文：

1. Introduction

 Lipomas

(1) Benign neoplasms of mature adipose tissue

(2) Relatively uncommon in the oral cavity, corresponding to 0.1% to 5.0% of all benign tumors at this anatomical site.

(3) Several histopathologic variants of lipoma have been identified in the oral cavity, including：

 Fibrolipoma

 Angiolipoma

 Chondrolipoma

 Chondroid lipoma

 Pleomorphic lipoma

 Spindle cell lipoma

 Sialolipomas

(1) Recognized as a distinct entity by Nagao et al.

(2) A well-demarcated proliferation of mature adipocytes with secondary entrapment of salivary gland elements.

(3) In both the major and minor salivary glands.

(4) More than 20 cases of sialolipoma have been reported in the English literature (Pubmed database).

 The present article

(1) Reports 4 additional cases of sialolipoma, all of them affecting the minor salivary glands

(2) Reviews the literature regarding clinicopathologic aspects, differential diagnosis, and therapeutic management of this recently recognized histologic variant of lipoma.

2. Case reports

Case 1 Case 2

Age

A 27-year-old woman A 73-year-old woman

Site

Posterior region of the lateral margin of the tongue

Left side of the floor of her mouth

Feature

 Painless, firm, pinkish nodule  Painless mass

 Well demarcated

 Covered with a nonulcerated mucosa of normal color

Size

1.0 × 1.0 cm 4.0 × 1.0 cm

Duration

5 years earlier (not mentioned)

(no picture)

Medical

history

unremarkable noncontributory

Clinical

diagnosis Fibroma Ranula

Excisional biopsy Excisional biopsy

Microscopi c analysis

 Proliferation of mature adipocytes

 Entrapped salivary gl. parenchyma showing atrophic mucous acini &

markedly dilated ducts.

 The adipose tissue accounted for about 50% of the tumor volume

 The glandular elements presented as sparsely distributed epithelial

 Proliferation of mature adipocytes

 Entrapped mucous acini and ducts of the minor salivary glands.

 The glandular parenchyma exhibited fibrosis, acinar atrophy, dilated ducts with foci of squamous metaplasia and oncocytic change

 A moderate lymphoplasmacytic inflammatory infiltrate

islands of variable size.

 Fibrosis, squamous metaplasia of duct cells

 A discrete lymphoplasmacytic inflammatory infiltrate.

 A sharp demarcation from the surrounding tissue was noted at the periphery of the tumor.

 The adipose tissue accounted for most of the tumor volume (65%)

 The glandular component presented as epithelial islands of variable size distributed throughout the tumor.

 A thin fibrous capsule was at the periphery of the tumor.

Definitive

diagnosis Sialolipoma Sialolipoma

Recovery

Uneventful Uneventful

Case 3 Case 4

Age

A 65 y/o female A 68 y/o woman

Site

Buccal mucosa Retromolar pad

Feature

 Painless nodule

 The overlying mucosa was intact and of normal color.

 Symptomatic,

 Well-demarcated

 Firm, pinkish swelling

Size

2.0 cm in max. diameter 0.9 cm in max. diameter

Duration

2 years earlier (not mentioned)

Medical

history

(not mentioned) (not mentioned)

Clinical

diagnosis Fibroma Fibroma

Excisional biopsy Excisional biopsy

Microscopi c analysis



A well-circumscribed tumor



Consisting of mature adipose tissue



The presence of entrapped salivary gland parenchyma showing fibrosis, acinar atrophy, and dilated ducts with foci of oncocytic change.



The glandular component presented as sparsely distributed epithelial islands



A discrete lymphoplasmacytic inflammatory infiltrate was superimposed on the glandular parenchyma.



The adipose tissue accounted for most of the tumor volume (60%).



A sharp demarcation of the tumor from the surrounding connective tissue



Proliferation of mature adipocytes enclosing the salivary gland parenchyma.



The glandular component presented acinar atrophy and ductal dilatation



The glandular component presented as sparsely distributed epithelial islands of variable size.



A discrete lymphoplasmacytic inflammatory infiltrate.



The adipose tissue accounted for 50% of the tumor volume



A thin fibrous capsule was at the periphery of the tumor.

definitive

diagnosis Sialolipoma Sialolipoma

Recovery

(not mentioned) (not mentioned)

3. Discussion

 Sialolipoma

(1) A histologic variant of lipoma

(2) Well-demarcated proliferation of mature adipocytes with secondary involvement of salivary gland parenchyma.

(3) Share similar clinical features with conventional lipomas, such as：

 A wide range in patient age

 The presence of a slow-growing and asymptomatic mass .

 Review of the previous 30 studies

case Author Age Sex Location Duration Size Treatment Follow-up

1 Nagao et al 20 M Parotid 4 mo 3.5 cm Superficial parotidectomy 91 mo

2 Nagao et al 45 F Parotid 10 y 6 cm Superficial parotidectomy 85 mo

3 Nagao et al 67 M Parotid 2 mo 1.7 cm Superficial parotidectomy 37 mo

4 Nagao et al 66 F Parotid 5 mo 6 cm Superficial parotidectomy 35 mo

5 Nagao et al 48 M Parotid 10y 6 cm Superficial parotidectomy 20 mo

6 Nagao et al 66 M Soft palate 72 mo 2.2 cm Surgical excision 11 mo

7 Nagao et al 75 M Hard palate 3y 1 cm Surgical excision NA

8 Hornigold et al 0 F Parotid 2.5 mo 3 cm Superficial parotidectomy 2 y

9 Lin et al 67 F Floor of mouth 1y 3 cm Surgical excision 2 y

10 Michaelidis et al 44 M Parotid 18 mo 3.5 cm Total parotidectomy 2 y

11 Sakai et al 60 F Hard palate 10 y 1.8 cm Surgical excision No evidence of disease 12 Walts and Perzik 48 M Parotid NA 3.5 cm Superficial parotidectomy No evidence of disease 13 Walts and Perzik 65 M Parotid 2 mo 2.6 cm Superficial parotidectomy No evidence of disease

14 Baker et al 44 M Parotid 2 mo 1 cm Superficial parotidectomy 30 mo

15 Fregnani et al NA NA Tongue NA NA Surgical excision No evidence of disease

16 Fregnani et al NA NA Buccal sulcus NA AN Surgical excision No evidence of disease

17 Ramer et al 84 F Buccal mucosa NA 1 cm Surgical excision 11 mo

18 Ramer et al 43 F Soft palate NA 2 cm Surgical excision NA

19 Parente et al [ 77 F Submandibular Months 3x2x1.8 cm Surgical excision 22 mo

20 Ponniah et al 60 M Floor of mouth NA 2 cm NA 2 y

21 Kadivar et al 3 F Parotid 7 mo 3 cm Surgical excision NA

22 Bansal et al 11 M Parotid 11 y 7x7 cm Surgical excision 1 y

23 de Freitas et al 38 M Lower lip NA 1 cm Surgical excision NA

24 Okada et al 66 F Hard palate 10 y 1.2x1x1 cm Surgical excision NA

25 Jang et al 62 F Submandibular 3 y 5 cm Surgical excision 17 mo

26 Dogan et al 33 M Parotid 1 y 2x2 cm Surgical excision No evidence of disease

27 Present study 27 F Tongue 5 y 1 cm Surgical excision 1.5 mo

28 Present study 73 F Floor of mouth NA 4 cm Surgical excision NA

29 Present study 65 F Buccal mucosa 2 y 2 cm Surgical excision NA

30 Present study 68 F Retromolar pad NA 0.9 cm Surgical excision 14 mo

(1) Age：A wide range in patient age

Affect from newborns to the elderly (mean age, 50.7 years).

(2) Sex/ Gender：

Although previous studies have reported a male preference, a review of the cases published so far revealed a slightly higher frequency of sialolipomas among females (53.6%).

(3) Site：

a) With respect to salivary gland type,

 15 (50%) of the 30 cases involved the minor salivary glands

 15 (50%) affected the major salivary glands.

b) Minor salivary gland sialolipomas：no preference for a specific site

c) Major salivary gland sialolipomas

 13 (86.7%) cases were observed in the parotid gland.

 Only 2 (13.3%) affected the submandibular gland.

(4) Clinically feature：

A slowly growing, asymptomatic swelling (5) Size：

 In the minor salivary glands, tumor size usually ranges from 0.9 to 4.0 cm in maximum diameter (mean, 1.7 cm).

 In the major salivary glands usually measure 1.0 to 7.0 cm in diameter (mean, 3.7 cm).

(6) Duration：

Quite variable, ranging from 2 months to 11 years (7) Initial clinical diagnosis：

a) In the minor salivary glands：

 Benign salivary gland neoplasms, such as:

○¹ Pleomorphic adenoma

○² Low-grade mucoepidermoid carcinoma.

 Our cases：

 3 of our cases the clinical diagnosis suggested was fibroma.

 1 in the floor of the mouth was clinically diagnosed as ranula.

 Similarly, Lin et al reported a case of sialolipoma involving the floor of the mouth that raised a clinical diagnostic hypothesis of ranula.

b) In the major salivary glands：

○¹ Salivary gland neoplasm

○² Lipoma

(8) Method of diagnosis：

a) Computed tomography(CT) & magnetic resonance imaging (MRI)

 Might be useful for the diagnosis of sialolipomas

 Sialolipomas appear as a well-circumscribed tumor presenting a low-intensity CT signal and high MRI intensity.

 Sakai et al reported a case of sialolipoma located in the palate：

 Soft palate

 Hard palate

 Tongue

 Buccal mucosa

 Floor of the mouth

 Buccal sulcus

 Retromolar pad

 Lower lip

 Hyperintensity on T1-weighted images& isointensity on T2-weighted images

 Features resembling those of subcutaneous fat.

 According to these authors, MRI suggested that the tumor apparently had extended into the subcutaneous fat.

(9) Histological：

a) Well-circumscribed lesions

b) Proliferation of mature adipocytes with secondary involvement of salivary gland parenchyma.

c) The glandular components：

 Consisted of regularly organized epithelial & myoepithelial elements

 Possessed normal specific cellular phenotypes and no proliferative activity, features seen in normal salivary gland tissue.

Thus, the glandular components probably become entrapped during lipomatous proliferation rather than representing true neoplastic elements.

 Presents variable degrees of acinar atrophy and ductal dilatation.

d) Slight differences in the proportion of adipose and glandular

components are observed according to the type of salivary gland affected.

 In the major salivary glands, adipose tissue accounts for 75% to 90%

of the neoplasm.

 In the minor salivary glands, lipomatous tissue accounts for 50% to 80% of their volume.

 Coherently, in the present cases, adipose tissue accounted for 50% to 65% of the tumor volume.

e) The glandular component consists of epithelial islands

 Sparsely distributed throughout the tumor.

 Occasionally, found at the periphery of the tumor.

 In some cases of sialolipoma located in the palate, the epithelial components were found to be clustered.

 In the present cases：

 The glandular component consisted of epithelial islands of variable size, sparsely distributed throughout the tumor.

f) Fibrous capsule：

 One of the histologic criteria for the diagnosis of sialolipoma is the identification of a fibrous capsule around the tumor.

 Almost all parts of the oral cavity contain salivary glands.

Thus, any intraoral lipoma that occurs at these sites might be intermingled with adjacent salivary gland elements.

 However, to diagnosis a sialolipoma in the context of minor salivary glands：

○¹ The amount of adipose tissue and glandular elements should be in equal proportions

○² Limited peripherally by a fibrous capsule.

g) Lymphocytic infiltration

h) Fibrosis, myxoid change in adipose tissue

i) Squamous and oncocytic metaplasia in ductal cells.

j) Sialolipomas encircling small nerve bundles

 Particularly sialolipomas affecting the major salivary glands.

 According to Michaelidis et al, this finding may suggest

○¹ A more aggressive mode of growth of these tumors than that attributed to ordinary lipomas

○² A multicentric proliferation of adipose tissue, ultimately entrapping interstitial normal structures.

k) Sialolipomas compared with common lipomas

 Fregnani et al：

○¹ Increased expression of proliferating cell nuclear antigen

○² Faster growth.

 Both showed no recurrence during the follow-up period.

(10) Differential diagnosis：

The microscopic differential diagnosis of sialolipoma should include lesions containing extensive adipose tissue, such as

 Lipomatous pleomorphic adenoma

 Lipomatosis

 Lipoadenoma

a) Lipomatous pleomorphic adenoma：

 Although adipose tissue can account for up to 90% of the tumor mass, the adenomatous tissue in these lesions shows typical features of pleomorphic adenoma, including ducts and sheets or strands of (dark-staining) epithelial cells.

b) Lipomatosis：

 A nonmalignant overgrowth of adipose tissue throughout the salivary gland parenchyma, resulting in the diffuse enlargement of the latter.

 Associated with diabetes mellitus, liver cirrhosis, chronic alcoholism, malnutrition, and hormonal disturbances.

 Lipomatosis vs. Sialolipomas：

Sialolipomas has a fibrous capsule.

c) Lipoadenomas：

 Well-circumscribed tumors with distinct adipose and glandular components, called adenolipomas or lipoadenomas, have been described in the breast, thyroid, and skin.

 These lesions consist of an admixture of mature fat cells and branching narrow epithelial tubules lined with columnar cells and supported by basal cells without myoepithelial differentiation.

 Lipoadenomas vs. Sialolipomas：

The lack of normal acinar structures in lipoadenomas

d) Sclerosing polycystic adenosis：

 Some cases of sclerosing polycystic adenosis may present a prominent lipomatous stroma.

 In contrast to sclerosing polycystic adenosis：

 Sialolipomas：

○¹ No proliferation of ductal or acinar cells.

○² No cellular atypia in the glandular component.

(11) Therapeutic management：

 In the parotid gland → Superficial parotidectomy.

 In minor salivary gland → Simple surgical excision.

(12) Prognosis：

 Despite the lack of follow-up data in some cases, no recurrence or malignant transformation has been reported so far.

4. Conclusion

(1) Sialolipoma is a rare histologic variant of lipoma, commonly observed in adults.

(2) When involving the minor salivary glands, these tumors show no preference for any site in the oral cavity.

(3) Although the diagnostic criteria and microscopic features of sialolipomas have been relatively well established, permitting the differential diagnosis with

other important lesions and/or conditions, many aspects regarding the histopathogenesis of these tumors are still unclear.

(4) Thus, further studies regarding this newly recognized histologic variant of lipoma should be performed, particularly using molecular biology techniques.

題號 題目

1

The following statements of lipoma, which is true?

(A) Most are in 20-years-old or younger patient (B) More common in obese people

(C) Most are more than 3 cm in size

(D) If the caloric intake is reduce, the size of lipoma decreases as normal body fat loss

答案(B) 出處：Brad W. Neville et al, Oral and Maxillofacial PATHOLOGY 3^rd edit, St. Louis, Missouti, USA: Saunders, Elservier; 2009. 523-524

題號 題目

2

Where is the most common site of intra-oral lipoma ? (A) Tongue

(B) Soft palate & the posterior part of the hard palate (C) Buccal mucosa & buccal vestibule

(D) Floor of the mouth

答案(C ) 出處：Brad W. Neville et al, Oral and Maxillofacial PATHOLOGY 3^rd edit, St. Louis, Missouti, USA: Saunders, Elservier; 2009. 523-524