histologic studies on lipogranuloma

Keio Journal of Medicine Vol. 3, No. 4, December, 1954

HISTOLOGIC STUDIES ON LIPOGRANULOMA

KENYA HORIE

Department of Pathology, School of Medicine Keio University

(Received on December 20th, 1954)

INTRODUCTION

It is not uncommon to see a peculiar granulomatous nodular reaction in

the fat tissue, especially in the subcutaneous fat tissue. This specific granulo

- matous reaction, which is clinically difficult to differentiate from malignant

tumor or tuberculosis, can be distinctly differentiated by biopsy findings from

malignant tumor or tuberculosis.

Abricosoff(1) (1926) is the first to name this reaction as lipogranuloma or

"lipophages Granulom", which has since greatly attracted the attention of

clinicians and pathologists.

Many discussions concerning pathogenesis and mechanism of the occur

rence of this lipogranuloma had been made (Abricosoff, Makai(2), Smetana(3),

FeijOo(4)).

I defined this lipogranuloma as a granuloma which is formed in fat tissue

representing productive process in the fat tissue resulting directly from degenera

tion and necrosis of fat cells.

Case studies were performed chiefly with biopsy materials.

MATERIALS AND METHODS

The seventeen cases presented in this study were taken from the files of

the Pathological Department of the School of Medicine, Keio University. (Table

1 and 2) All the specimens were fixed in formaldehyde solution, and the

clinical diagnosis for these were various as follows: epididymitis tuberculosa,

mammary tumour, fibroadenoma mammae, fibroma mammae, Darier-Roussy's

sarcoidosis, Weber-Christian's disease, operations scar, mammary cancer or

hematoma, lipoma and lipogranuloma, etc.

The staining -methods employed are as follows : hematoxylin-eosin stain,

Mallory's stain, Van-Gieson's stain, special stains for elastic fibers and also

reticulum fibers, iron reaction, special stain for tubercle bacillus, PAS staining,

and when wet tissues were available, the following stains were performed in

frozen section: sudan ‡V, oil red 0, nile blue sulphate. Additional examinations 215

216 KENYA HORIE

were made for double refraction and autofluorescence. Also Smith-Dietrich's

lipid staining and Schultz's cholesterol staining were performed.

Table 1

Clinical Findings of the Typical Lipogranuloma

Table. 2

Clinical Findings of the Atypical Lipogranuloma

HISTOLOGIC FINDINGS

Among the seventeen cases studied, lipogranuloma was noticed occurring

in two men, thirteen women and two persons of unknown sex, the ages varying

between 16 and 64 years. The duration of the disease from the onset to the

time of operation varied from 20 days to 17 months. In eleven instances the

subcutaneous adipose tissue was the site of the primary lesion, while in four

the mammary tissue, and in one the epididymis.

The number of granulomas in each patient was multiple in five of the

cases, while in twelve cases single. The geneses of these lipogranuloma are

almost unknown. In briefly summarizing the microscopic findings of these

seventeen cases of lipogranuloma, it was considered, to the author's opinion,

STUDIES ON LIPOGRANULOMA 217

that lipogranuloma should be classified in two types, one as a typical lipogra

nuloma, the other as an atypical type.

a. The Typical Lipogranuloma

Among the seventeen cases twelve belong to this type. (Table 1) The

microscopic findings of these twelve cases are almost all the same but with

minor variations, and are briefly summarized as follows. (Fig. 1 and 2)

The histologic pictures of the lesions in these cases revealed definite disrup

tion of the usual structure of the subcutaneous adipose tissue, and the normal

fat cells were replaced by fat globules of varying sizes, sometimes smaller but

often much larger than the original structures.

Hyaline necrosis was often noticed in the intercellular septums. The

affected septums were noticed swollen and thickened, eosinophilic hyaline sub

stance being deposited within these swellings.

The nuclei of the fat cells and septal cells were altered, disintegrated and

finally disappearing. The fat droplets which were liberated from the fat cells

by disruption of both the fat cells and the septums, frequently coalesced in

a great extent forming globules of a considerable size or sometimes of a small

size, that is, in other words, the adipose tissue were apparently replaced by fat

globules. Fat globules were seen in the center of the lesion and were often

surrounded by the epitheloid cells with spindle-shaped nuclei or giant cells

of the foreign body type and sometimes of the Langhans' type and syncytial type.

The histiocytes transported into the fat cells were noticed in the inner wall

of the fat cells surrounding the fat globules with continous rows. Macrophages,

usually distended with fat droplets, were conspicuous about the lesion. The

cytoplasm of such cells was reduced to thin, fragile webs surrounding the

phagocytosed fat droplets.

Focal lymphocytic infiltrations were usually present, however, polymor

phonuclear granulocytes, plasmocytes and eosinophilic granulocytes were either

absent or inconspicuous. Globules of free fat became entrapped by the proliferat

ing fixed tissue elements forming connective tissue. Preexistant elastic fibers

within the affected areas were disrupted, but those of the vessels outside the

lesion appeared unaltered.

The argentophilic reticulum fibers surrounding fat cells or in the septums

between the fat cells were disrupted, condensed and were replaced by collagen

fibers showing a tendency to hyalinization.

Surrounding the lipogranulomatous lesions the collagen fibers increased

reactively. No or scarce hemosiderin pigment was found in or near the

218 KENYA HORIE

granulomatous areas. It seems likely that there were no indications of a pro

found change in the subcutaneous fat tinctorially.

Staining granulomatous lesions with sudan ‡V and oil red 0, it was noticed

that the tinctorial attitude was almost the same with the neutral fat in normal

fat tissue. However, staining the granulomatous lesions wih nile blue sulphate,

it was revealed that the colour changed from red to purple, differing from the

redness on the neutral fat contained in the cells of the normal subcutaneous

adipose tissue.

Double refractivity, autofluorescence, Schultz's cholesterol reaction and

Smith-Dietrich's lipoid reaction of the altered fat tissue were all of negative

results. Staining of tubercle bacillus showed negative results in all preparations.

(Table 3) Needle-shaped crystals of yellow colour were found in one case, but

they were insoluble to alcohol and aceton, showing no evidence of the crystals

to be fatty acids or soaps. (Fig. 3) In another case (No. 11) endophlebitis

productiva was found.

b. Atypical Lipogranuloma .

Five cases belong to this type. The histologic findings of these five

cases revealed similar histologic pictures in all cases but with minor variations,

and the results obtained were as follows :

This type is characterized by its cyst formation, the content of the cyst

being fat. Some of these fat cysts were large enough to become visible to

the naked eye. At the inner wall of these fat cysts papillomatous structure

was often observed. (Fig. 4 and 5) Small cysts frequently coalesced by dis

ruption of the septums, formed cysts of a considerable size. (Fig. 4, 6 and 7)

On the surface of this papillomatous structure a certain lining substance,

which ressembled ghosts of the epithelium being eosinophilic and also protoplasma

-like, was found.

In higher magnification, nucleus was never found in the above-mentioned

lining substance, and this eosinophilic, protoplasma-like substance was stained

red with the PAS method for mucopolysaccharides and never digested with

diastase, and stained distinctly with some of the fat staining methods.

Reticulum fibers were thickened and existed under this lining substance.

Syncytial and foreign body giant cells and epitheloid cells were found in the

inner wall of this cyst, and the reticulum fibers were occasionally found either

under these cells or upon these cells. However, in the majority of the cases the

reticulum fibers were noticed distinctly destroyed at the site of cells. (Fig. 8)

In the inner walls of the small cysts these productive changes were not


evident, but these small cysts coalesced with each other and formed large cysts.

During this process of formation of the large cysts, the eosinophilic lining

substance, giant cells and epitheliod cells were noticed to be formed. In one

peculiar case bone formation, which is a rare condition, was found, the thickened

reticulum fibers membrane underlying the bone formation.

The outer walls of these cysts were thin layers of collagen fibers, and in

the peripheries of the lesions small round cells, histiocytes and lipophaged

macrophages which phagocytized the fat and the PAS positive substance, were

noticed scattering, while the plasma cells and eosinophilic leucocytes were

hardly noticed.

In comparison with the typical lipogranuloma, these cell infiltrations were

lesser and the lesions were more localized in this atypical type.

The deposit of hemosiderin pigment around the cysts was more numerous

than the typical type.

The reticulum fibers of the normal fat cells were noted disappeared in the

cysts, only remaining as destroyed debris of fibers, while at the cyst wall the

reticulum fibers were observed thickened and condensed. The elastic fibers were

noticed increased in the lesions. The layer of collagen fibers of the outer wall

of the cyst was more thickened and condensed than the typical type.

The fat staining of the content of the cysts revealed the following results:

staining with oil red 0, the content was demonstrated deep red; with nile blue

sulphate, blue; occasionally autofluorescence examination revealed positive results.

(Table 3) The fat staining attitude of this atypical lipogranuloma was different

from the normal fat tissue or from the typical lipogranuloma. However, by

Table 3

Histologic Comparison of the Typical Lipogranuloma with the Atypical Lipogranuloma

220 KENYA HORIE

staining with sudan ‡V yellow red color was revealed, while the double refrac

tivity, Smith-Dietrich's lipoid reaction and Schultz's cholesterol reaction of the

same revealed negative data.

DISCUSSION

Lipogranuloma can be defined as a productive reactive process connected

with the degenerated and liberated fat following degeneration and necrosis of

fat cells when adipose tissue was injured by an unknown genesis.

The chain of events leading to this particular reaction, however, is by no

means clear, and there are probably a number of different etiologic factors

initiating the changes which result in histologically similar reactive processes.

In some instances the lesions are inflammatory and multiple, and in traumatic

or perifocal lesions the reactions are single. And it is known, that similar

reactions are observed in the tissue lipide materials being artificially introduced.

(Smetana, Brody(5), Weidman(6), Sutton(7), Burrows(8)).

This would suggest that the tissue reaction is dependant on the presence

of mildly irritating, unphysiologic lipide substance derived from either endogenous

or exogenous source.

Lipase has long attracted the attention of pathologists. Fatty acids and

soaps are formed from neutral fats subsequent to the action of a lipase. It

is difficult, however, to make evident the actual occurrence bf such a trans

formation or its possible relationship to the differences between lipogranulomas

of different origin. It has been assumed that lipase either derived from injured

fat cells, from which it is liberated during the distruption of the tissue, or is

carried to the injured area by the blood stream. Crystals and amorphous material,

compatible in appearance with fatty acids and soaps, have often been observed

in human tissues showing "fat necrosis, and in animal tissues after artificial

production of comparable lesions. However, caution must be exercised in the interpretation of these crystals, as crystallization of neutral fats can occur

during fixation.

Lecene and Moulonguet(9) insisted that the intracellular transformation of

neutral fats into fatty acids and soaps constituted the primary and basic factor,

basing their interpretation of the staining reactions of fats and products of

hydrolysis to nile blue sulphate. But the staining reaction of nile blue sulphate

to fatty acids and soap is not reliable.

Artificially introduced fats and oils, for which the body probably has no

effective lipases, produce a lipogranuloma, This lipogranuloma occurs at the

location of injection in the absence of necrosis of tissue, indicating that these


foreign substances, despite assumed inertness, exercise an irritating action on

tissues.

The highly irritating action of products of hydrolysis and saponification of

fats is well known; their presence are manifested in pancreatic fat necrosis.

There appears to be a definite relationship between the chemical nature of the

lipide material and the cellular response.

The question arises whether the intracellular saponification, proposed by

Lecene and Moulonguet precedes the necrosis of fat cells and stroma or is

dependant on it.

There is inflammatory component following necrosis of tissue, including

fat, the lipogranulomatous process continues long after a lesion produced in

other tissues would have healed. If hydrolysis and saponification of fats were

responsible for the tissue reaction, one would expect resolution after a reasonable

period, some of the fatty acids are soluble and can be absorbed, whereas insoluble

ones frequently form soaps and may be deposited as calcereous materials.

Although calcification did occur in my cases, it is certainly not an essential feature

of the lipogranuloma. Bone formation was found in one of the cases of atypical

lipogranuloma.

Sometimes the granulomatous process extends into the neighboring areas,

causing changes identical with those seen in the original lesion. It is often

misconceived clinically to be a neoplasm, causing its absence of significant clinical

signs of an inflammatory reaction, and suggesting a neoplastic growth. Some

times non-inflammatory enlargement of regional lymph nodes caused when

macrophages transporting fat from the lipogranuloma are active, gives the

clinical impression of matastasizing growth. Many cases are misdiagnosed

clinically as tumours in my cases, although lymphnodes are not examined. It

is considered that not only the persistence but also the apparent progression of

lipogranuloma are due to a focal cyclic biochemical process, secondary to the local

disturbance of tissue metabolism.

There are no known specific enzymes for liquid petrolatum or vegetable oils

in the body. If soap formation and calcification follow splitting and hydrolysis,

why do they occur after introduction of vegetable oils? If fatty acids formed

by hydrolysis represents highly irritating breakdown products of fats, why is

there no purulent tissue reaction in lipogranuloma comparable to the reaction

following artificial introduction of vegetable oils with a high fatty acid content?

Unless these questions are solved satisfactory, the hitherto mentioned lipase

theory may not be perfectly understood.

It is recognized histologically and experimentally that these predominant

222 KENYA HORIE

cells in lipogranuloma are histiocytic cells. These histiocytic cells remove the

altered fat by transporting it as the phagocytes from the areas of degenerated

and disrupted adipose tissue. They invade into the altered fat cells, and then

the hyperplasia of epitheloid cells occurs around the fat globule. The hyperplasia

of the epitheloid cells, foreign body giant cells, Langhans' giant cells and

syncytial cells is active. And in later stages the scar tissue is formed by fibrosis

around the lesions (Fig. 9).

Formation of the Typical & Atypical Lipogranuloma

Fig. 9

Deposition of hemosiderin pigment is noticed in moderate degree around

the cyst of atypical lipogranuloma, while in typical cases it is absent or scarce.

The deposition of hemosiderin pigment is a factor, which suggest that lipo

granuloma is related to trauma, but clinically there were no evidence of injury

in the majority of the cases,


The infiiltration of polymorphonuclear granulocytes is slightly found in

a case diagnosed Weber-Christian's disease.

Lipogranuloma was classified as above in two groups : that is, a typical type

and an atypical type, between which evident differences were found histologically.

(Fig. 9, Table 3)

Namely in the atypical cases cysts are always found, the lipide in the cysts

is stained blue with nile blue and had the autofluorescence differing from the

typical one, and deposition of hemosiderin pigment around the cyst is found

slightly.

Abricosoff reported cyst formation, in which he saw serous fluid, Makai and

Goldzieher(10) reported the cyst, in which they saw lipide, and Makai expressed

the belief that the giant cells originated from proliferating capillary endothelium.

The various authors such as Abricosoff mostly agree with the conception that

the cysts are produced in the later stages.

The contents of the cysts in my cases are lipide, and it is recognized that the

cysts are formed by confluence of the fat cells, septum of which are destroyed,

the cysts enlarged and there the papillary remnants of the septums of the fat

cells in the cysts are noticed remaining. In the inner surface of the cyst wall

a layer of epitheloid substance is found, which is stained positive by PAS

method, and is considered to contain lipide and degenerated protein.

The inner walls of the cysts are formed by epitheloid cells originating from

the histiocytes and monocytes, and there is scarcely any evidence that shows the

contents to be fatty acids. Although it is a pertinent opinion that the cyst

formation is seen in the later stages, it is not uncommon to see the cyst forma

tion occurring also in the early stages, and even in the long clinical course cyst

formation is not always found.

From these points of view, lipogranuloma in which cyst formation was found

should be classified as atypical cases. Additionally, the results of lipide staining

in these two types, the typical and atypical cases, are as follows: with oil red O

lipide of the former type is stained red, while that of the latter is stained deep

red; and in nile blue sulphate preparations it is observed that lipide of the former

is stained red to purple, on the other hand that of the latter is stained blue in

the majority of the cases; autofluorescence is recognized clearly in the lipide of

the latter, but no recognized in that of the former.

These facts suggest that there are tinctorial differences between the qualities

of both lipids. The deposition of hemosiderin pigment is somewhat numerous in

the atypical lipogranuloma than in the typical ones which is deposited with only

a few or no hemosiderin pigment.

224 KENYA HORIE

There are many opinions concerning the genesis of the lipogranuloma

(Fejoo). It is said that lipogranuloma is formed by blood lipase acting on

traumatized fat when hemorrhage occurred following the trauma. (Abricosoff,

Smetana) In general, trauma of varying nature and intensity ranks prominently

as the proposed initiating factor.

Productions of the lipogranuloma by experimental traumatic lesions are

reported. The cause of adiponecrosis neonatorum appears uncertain, although it

is said often relating to traumatic ischemia of subcutaneous tissues (Smetana).

On the other hand, some authors suggest the possibility of ischemia as one of

the causative factors by the existence of vessel lesions. However, there is ques

tions whether this opinion concerning trauma is right. Harbit(11) reported

multiple lipogranulomas developing in the wake of trauma.

Constitutional and endocrine factors were reported to be necessary in forming

lipogranuloma by Makai and Goldzieher, Makai further suggested the relation

of thyroid gland in the occurrence.

An inflammatory process is discussed since Abricosoff as a cause of lipo

granuloma, which is microscopically indistinguishable from that following physical

injury. There are cases of lipogranuloma, which are clinically diagnosed as

Weber-Christian's disease, Darier-Roussy's sarcoid or tuberculide.

Abricosoff suggests the formation of the lipogranuloma as the subcutaneous

adipose tissue influenced by local toxic agent from his findings of lipogranuloma

of fleck fever or recurrent fever.

Endogenous agents, toxins, drugs, vaccinations, bacteria, chronic focal infec

tions and allergic reactions are considered as pathogenetic factors, although the

actual role of any of these factors to the lesion has never been proved.

However, it seems possible that local shock may produce temporary ishemia,

perhaps from spasm of arterial vessels or from organic vessel lesions, thus

producing a local necrosis of fat tissue and thus forming the lipogranuloma.

From the finding of the productive endophlebitis in one of the cases studied,

local circulatory disturbance was presumed as a possible causative factor in the

occurrence of the lipogranuloma.

SUMMARY

From the histologic studies in seventeen cases of lipogranuloma, two types,

the typical and the atypical type, were differentiated. Among the seventeen

cases, twelve cases were typical lipogranuloma cases, while five were atypical

cases. The atypical lipogranuloma is characterized by its cyst formation. Some

observers have the opinion that the cyst formation occur in later stages, however,


in my cases, cyst formation was even found in early stages. It is considered,

to the author's opinion, that the lipogranuloma with cysts should be differentiated

from the typical type. Further, between these two types of lypogranuloma

tinctorial differences were noticed by the lipide staining method.

The causative mechanism of the formation of lipogranuloma was considered

to be not a simple one. When a certain cause, either traumatic or inflammatory,

etc., happen to act in an individual with the disposition, first lesion occurs in the

vessel, which leads the degeneration and necrosis of the fat tissue. The liberated

fat also degenrates, however, in this case whether lipase is closely connected

with this degeneration or not is not clear. Around this degenerated fat arises

the productive reaction chiefly consisted of giant cells, epitheloid cells and

histiocytes, and finally fibrosis occurs.

In one case bone formation was found in the wall of the cyst.

The author wish to express his gratitude to Prof. Tadayoshi Kobayashi

for suggesting this investigation as well as for constant guidance in the

course of the work. Thanks are also due to Prof. Yoshio Kusama for reading

and revising the manuscript.

REFERENCES

1. Abricosoff, A.: Zentralbl. f. allg. Path. 38: 542, 1926; Verhandl. d. deutsch. Path.

Gesells. 24: 57, 1929.

2. Makai, E.: Klin. Kochnschr. 7: 2343, 1928.

3. Smetana, H. F. & Bernhard, W.: Arch. Path. 50: 3, 296, 1950.

4. FeijOo, L.: Frankf. Z. Path. 65: 173, 1954.

5. Brody, H.: Arch. Path. 35: 5,744, 1943.

6. Weidman, F. D. & Jefferies, M. S.: Arch. Dermat. & Syph. 7: 209, 1923.

7. Sutten, I. C.: Arch. Dermat. & Syph. 7: 223, 1923.

8. Burrows, M. T. & Johnston, C. G.: Arch. Int. Med. 36: 3, 293, 1925.

9. Lecene, P. & Moulonguet, P.: cit. from Smetana, H. F.

10. Goldzieher, M. A.: Arch. Surg. 23: 691, 1931.

11. Harbitz, H. F.: Acta chir. Scandinav. 76: 401, 1935.

Fig. 1 Fig. 2

Fig. 3 Fig. 4

Fig. 1 Typical lipogranuloma (case 5). A nodule in the subcutaneous adipose tissue noticeable. (Hematoxylin-eosin stain. Low power)

Fig. 2 Typical lipogranuloma (case 6). Epitheloid cells and giant cells are noticed around the fat globules. (Hematoxylin-eosin stain. Low

power)

Fig. 3 Typical lipogranuloma (case 1). Many crystals which are insoluble with alcohol are noticed. (Hematoxylin-eosin stain)

Fig. 4 Atypical lipogranuloma (case 2). Large cyst formation noted. (Hematoxylin-eosin stain. Low power)

KENYA HORIE

Fig. 5 Fig. 6

Fig. 7 Fig. 8

Fig. 5 Atypical lipogranuloma (case 1). In the cyst wall, a marked papillary structure with accompanying eosinophilic lining substance is noted. (Hematoxylin-eosin stain. High power)

Fig. 6 Atypical lipogranuloma (case 1). Degeneration and necrosis of fat cells, further fat cells coalescing into large fat cyst are notice able. (Hematoxylin-eosin stain. Low power)

Fig. 7 Atypical lipogranuloma (case 1). Higher magnification of a por tion of the lesion shown in Fig. 6. (Hematoxylin-eosin stain)

Fig. 8 Atypical lipogranuloma (case 2). A foreign body giant cell is noted in the cyst wall. (Hematoxylin-eosin stain. High power)

KENYA HORIE

histologic studies on lipogranuloma

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