An Infantile
Case of Infiltrating
Lipoma in the Buttock
By Masayuki Kubota, Akira Nagasaki, Hiroshi Ohgami, Takashi Kawanami, Youichiro Hachitanda, Katsuo Sueishi, Hideo Onitsuka, and Junji Murakami Fukuoka, @This paper presents a rare case of infantile infiltrating lipoma in the buttock. The usefulness of magnetic resonance imaging of the tumor in the follow-up study is discussed. Copyright o 1991 by W.B. Saunders Company INDEX WORDS:
Lipoma, infiltrating,
buttock.
L
IPOMA IS THE most common soft tissue tumor, usually encapsulated and superficially located. However, deep-seeded lipomas with intramuscular infiltration have been reported sporadically. Most occur in patients more than 40 years of age and arise in large muscles of the extremities. We describe a rare case of infiltrating lipoma in the left buttock diagnosed by surgical biopsies in the infantile period. The computed tomographic (CT) and magnetic resonance imaging (MRI) of the tumor, clinical and surgical aspects of this lesion, and differential diagnoses are discussed. CASE REPORT This 6-month-old boy was born as the third child of nonconsanguineous healthy Japanese parents. The family history was not contributory. The parents noticed the mass in the left buttock 1 month prior to admission. They consulted the section of pediatric surgery for gradual increase in size of the mass. On physical examination, his physical development was proportional to his age and neurological examination did not show any abnormalities. A soft, nontender mass (6 x 8 cm) was found to involve the lower half of the left buttock. The tumor was ill-defined, with the deep part anchored to the gluteal muscle. Ultrasonographic examination showed solid echogenic mass mixed with the gluteal muscle. A CT study showed homogeneous density mass replacing roughly the lower half of the left gluteal muscles, and protruding inferiorly into the subcutaneous tissue (Fig 1). Lipomatous nature of the neoplasm was suggested because of its low attenuation. Surgical exploration was performed. The tumor was not encapsulated. A deep part of the subcutaneous tissue with high consistency was gradually mixed with the striated muscle. Because complete separation of the tumor from the muscle layer was practically impossible, the protruding part of the tumor was excised for histological diagnosis. Histological study of serial sections of the resected specimen showed that the tumor consisted of mature fat cells mixed with bundles of striated muscle in a diffuse manner. Cellular atypism was not observed in any of the sections examined
From the Sections of Surgery and Radiology, Fukuoka Children’s Hospital, and the 1st and 2nd Depaltments of Pathology, and the Department of Radiology, Kyusyu University, Fukuoka, Japan. Address reprint requests to Masayuki Kubota, MD, Department of Pediatric Surgery, Faculty of Medicine, Kyusyu University, Maedashi 3-I-1, Higashi-ku, Fukuoha 812, Japan. Copyright o 1991 by W.B. Saunders Company 0022-3468/91/2602-0032$03.OOlO
230
Japan
(Fig 2). Diagnosis of infiltrating lipoma, intramuscular type, was made. The postoperative course was uneventful. The patient has been followed for about 9 months. CT (Fig 3) and MRI (Fig 4) at the age of 15 months showed that the lower half of the gluteal muscles were involved by the tumor for the whole thickness of the muscle layer, and extended inferiorly involving the sciatic nerves. At present, orthopedic examination of the patient does not show any abnormalities in gate or other physical development. DISCUSSION Paget reported the first case of infiltrating lipoma in the trapezius muscle in 1856, according to Behrend.’ Regan et al used the infiltrating lipoma to denote the lipomas originating in the intramuscular fat tissue and showing tendency of local recurrence in 1946.’ Greenberg et al classified these into two types (intermuscular or intramuscular) in 1963.3 The intermuscular type arises from the intermuscular fascial septa and invades the surrounding muscle layer across the fascial septa; the intramuscular type originates between the muscle fibers within the muscle bundles themselves and infiltrates adjacent muscles. Of these two types, the intermuscular type is more common and readily excised. Recent data are listed in Table l.‘-14In addition to these, Kindblom et al reported 46 cases of infiltrating lipoma, 34 of which were the intramuscular type. The tumors usually involve large muscles of extremities, especially the thigh and upper arm, and arise in all ages, but mainly adults in the 4th to 6th decades. Kindblom reported that tumors were more common in men than in women (male-female ratio, 27:19),” but the male to female ratio is 1:l in Table 1. Because most tumors are slow-growing and painless and often become apparent only with muscle contraction, surgical intervention is usually postponed until mass is sufficient to induce deformity, swelling, and pain. Winkler et al reviewed four pediatric cases of infiltrating lipomas with adequate histological documentation.14 Including the case reported therein, two of five cases were found to have mass on the forearm or back dating since birth, but ages at surgical exploration were 11 years in both cases. The present patient may be the youngest case of intramuscular lipoma, diagnosed at surgical exploration in the infantile period. Although differential diagnosis of a infiltrating lipoma includes various type of soft tissue tumors, consideration is usually limited to the typical lipoma, angiolipoma, and liposarcoma when size, location, consistency, and clinical course are assessed. On JournalofPediatric
Surgery, Vol26, No 2 (February), 1991: pp 230-232
Fig 1. Representative CT scan before operation. Note that the left gluteal muscle is replaced by the homogeneous low-density mass. Layered structure of the affected gluteal muscles can be observed.
microscopic examination, simple lipoma is composed of lipocytes with varying amounts of fibrous tissue and circumscribed by a delicate fibrous capsule. Infiltrating lipoma is also composed of mature lipocytes, but they infiltrate muscle in a diffuse manner without a few changes of striated muscle fibers. Cautions are necessary in diagnosis of well-differentiated liposarcoma, typically showing lipoblasts or cells with atypical nuclei. However, some cases of well-differentiated liposarcomas can be shown only by serial sections. Infiltrating angiolipoma is characterized by a striking predominance of blood vessels and a greater amount of connective tissue mixed with mature adipose tissue. A sonogram is effective to elucidate the echogenic nature of mass suggestive of adipose tissue, but often fails to delineate the exact outline of the tumor and its relationship to the surrounding muscle layer. CT is a useful diagnostic tool in the evaluation of these tumors based on differences in tumor density.16 Infiltrating lipomas usually appear as homogeneous fatdensity masses with well-defined margins and/or internal septations in the muscle layers in computed
Fig 3. Representative CT scan 6 months after operation. Almost the same level as in Fig 1. There seems to be no change in the nature of the tumor before and after operation. Size of the tumor was slightly expanded.
tomography. However, CT imaging of the tumor in the present patient was atypical in the sense that the fatty density component was homogeneously mixed with muscle bundles. MRI is a newly establi s?ed technique of imaging
6
i
Fig 2. Hematoxylin and eosin stain of biopsy specimen. The tumor consists of mature lipocytes penetrating into striated muscles in a diffuse manner. Note the complete absence of cellular etypism. (Original magnification x 144)
Fig 4. (A) Representative MRI scan of the tumor 6 months after operation (axial scan). Same level as in Fig 3. The tumor is represented as a homogeneous high-intensity mass and distinguished from the surrounding muscle layer. (6) Coronal scan of the tumor. Note that roughly half the gluteal muscles are involved.
232
KUBOTA ET AL
Table 1. Infiltrating Lipomas in the Literature Age at Studv
Sex
Diagnosis (vr)
Site
Size (cm)
Adir et al4
M
11
Forearm (L)
Hoffman et al*
F
42
Leg (R)
22 x 18 x 11
Regan et al2
M
8
Leg (R) Leg and foot
6X6
Osthuizen et ale
M
5th decade
Dempster’
M F
4mo 46
Gold et ala Greenberg et al3
F
0 x 4.5 x 3.5
Leg (L) Leg (L)
18
45
Forearm (R)
6x6~4
F
50
Thigh (R)
13.5 x 10 x 5.5
F
67
Thigh (R)
7X7X3
M
66
Thigh (L)
F
73
Thigh (L)
M
38
Leg (R)
20x4~6
M F
69
Leg (L) Upper arm
3 x 3.5 x 3.5
M F
48 59
Thigh (R)
13x7~6
Forearm (R)
3 x 1.5 x 1.0
M
43
Thigh (R)
45 x 25 x 13
M
58
Thigh (L)
18 x 12 x 4
Fetell et al”
F
12
Gastrocnemius (R)
Benhoff et alI2
M
11
Submandibular (L)
Austin et al”
F M
56 37
Thigh
12x9x6
Thigh
22 x 8.5 x 6.5
F
69
Thigh
10.5 x 10 x 5.5
F
10
Back
3x
Davis et al9 Dionne et al”
Winkler et al”
66
17X11X4
3x5
10
Abbreviation: L, left; R, right.
without radiation exposure. The usefulness of this technique is now widely appreciated. It was found that MRI of the tumor was effective in the evaluation of this patient. Fat tissue mixed with striated muscles appeared as higher intensity area than the surrounding muscle layer. Furthermore, the coronal view is useful in evaluation of exact anatomical relationship of the tumor to the surrounding tissue. Complete excision is the treatment of choice. Reportedly, the recurrence rate varied from 3%” to 62.5%,10 probably depending on the completeness of
the excision. However, in the present patient complete excision was avoided because of the possible occurrence of disturbances in the gate and physical development. Therefore, careful follow-up over the patient’s lifetime is necessary. We found that both CT and MRI had good resolution in imaging of the infiltrating lipoma in this patient. However, MRI is a more suitable diagnostic modality than CT, in the sense that multiplanar sections of the tumor are available and the unfavorable effect of radiation on the growing tissue can be eliminated.
REFERENCES 1. Behrend M: Intermuscular lipoma-report of three cases. Am J Surg 7:857-860,1929 2. Regan JM, Bikle WI-I, Broders AC: Infiltrating benign lipomas of extremities. West J Surg 54:87-93,1946 3. Greenberg SD, Isensee C, Gonzalez-Angulo A, et al: Infiltrating lipoma of the thigh. Am J Clin Path01 39:66-72,1963 4. Adir FE, Pack GT, Ferrior JH, et al: Lipomas. Am J Cancer 16:1104-1120,1932 5. Hoffmann HOE: Glomus and intramuscular lipoma: Reports of two cases. Mayo Clin Proc 16:13-16, 1941 6. Osthuizen SF, Barneison J: Two cases of lipomatosis involving bone. Br J Radio1 20:426-432,1947 7. Dempster WJ: Intermuscular lipomata. Br J Radio1 25:553555,1952 8. Gold AA, Oppenheim A: Deep intermuscular lipoma of an extremity. J Bone Joint Surg 36:146-1481954 9. Davis C Jr, Gruhn JG: Ginat lipoma of the thigh. Arch Surg 95:151-156, 1967
10. Dionne GP, Seemayer TA: Infiltrating lipoma and angiolipomas revisited. Cancer 33:732-738, 1974 11. Fete11 MR, Dully PE, Rowland LP: Infiltrating lipomas: A cause of monometric hypertrophy. Muscle Nerve 1:75-80, 1978 12. Benhoff DF, Wood JW: Infiltrating lipomata of the head and neck. Laryngoscope 88:839-848,1978 13. Austin MR, Mack GR, Townsend CM, et al: Infiltrating (intramuscular) lipomas and angiolipomas. A clinicopathological study of six cases. Arch Surg 115:281-284,198O 14. Winkler M, Petrelle N, Cohen A: Pediatric infiltrating lipomas: Case report and review of the literature. J Surg Oncol 35:59-62,1987 15. Kindblom LG, Angervall L, Stener B, et al: Intermuscular and intramuscular lipomas and hibernomas: A clinical roentgenologic, histologic and prognostic study of 46 cases. Cancer 33:754762,1974 16. Varma DGK, Muchmore JH, Mizushima A: Computed tomography of infiltrating benign lipoma. J Comput Assist Tomogr 11:45-49,1987
Case of Infiltrating
Lipoma in the Buttock
By Masayuki Kubota, Akira Nagasaki, Hiroshi Ohgami, Takashi Kawanami, Youichiro Hachitanda, Katsuo Sueishi, Hideo Onitsuka, and Junji Murakami Fukuoka, @This paper presents a rare case of infantile infiltrating lipoma in the buttock. The usefulness of magnetic resonance imaging of the tumor in the follow-up study is discussed. Copyright o 1991 by W.B. Saunders Company INDEX WORDS:
Lipoma, infiltrating,
buttock.
L
IPOMA IS THE most common soft tissue tumor, usually encapsulated and superficially located. However, deep-seeded lipomas with intramuscular infiltration have been reported sporadically. Most occur in patients more than 40 years of age and arise in large muscles of the extremities. We describe a rare case of infiltrating lipoma in the left buttock diagnosed by surgical biopsies in the infantile period. The computed tomographic (CT) and magnetic resonance imaging (MRI) of the tumor, clinical and surgical aspects of this lesion, and differential diagnoses are discussed. CASE REPORT This 6-month-old boy was born as the third child of nonconsanguineous healthy Japanese parents. The family history was not contributory. The parents noticed the mass in the left buttock 1 month prior to admission. They consulted the section of pediatric surgery for gradual increase in size of the mass. On physical examination, his physical development was proportional to his age and neurological examination did not show any abnormalities. A soft, nontender mass (6 x 8 cm) was found to involve the lower half of the left buttock. The tumor was ill-defined, with the deep part anchored to the gluteal muscle. Ultrasonographic examination showed solid echogenic mass mixed with the gluteal muscle. A CT study showed homogeneous density mass replacing roughly the lower half of the left gluteal muscles, and protruding inferiorly into the subcutaneous tissue (Fig 1). Lipomatous nature of the neoplasm was suggested because of its low attenuation. Surgical exploration was performed. The tumor was not encapsulated. A deep part of the subcutaneous tissue with high consistency was gradually mixed with the striated muscle. Because complete separation of the tumor from the muscle layer was practically impossible, the protruding part of the tumor was excised for histological diagnosis. Histological study of serial sections of the resected specimen showed that the tumor consisted of mature fat cells mixed with bundles of striated muscle in a diffuse manner. Cellular atypism was not observed in any of the sections examined
From the Sections of Surgery and Radiology, Fukuoka Children’s Hospital, and the 1st and 2nd Depaltments of Pathology, and the Department of Radiology, Kyusyu University, Fukuoka, Japan. Address reprint requests to Masayuki Kubota, MD, Department of Pediatric Surgery, Faculty of Medicine, Kyusyu University, Maedashi 3-I-1, Higashi-ku, Fukuoha 812, Japan. Copyright o 1991 by W.B. Saunders Company 0022-3468/91/2602-0032$03.OOlO
230
Japan
(Fig 2). Diagnosis of infiltrating lipoma, intramuscular type, was made. The postoperative course was uneventful. The patient has been followed for about 9 months. CT (Fig 3) and MRI (Fig 4) at the age of 15 months showed that the lower half of the gluteal muscles were involved by the tumor for the whole thickness of the muscle layer, and extended inferiorly involving the sciatic nerves. At present, orthopedic examination of the patient does not show any abnormalities in gate or other physical development. DISCUSSION Paget reported the first case of infiltrating lipoma in the trapezius muscle in 1856, according to Behrend.’ Regan et al used the infiltrating lipoma to denote the lipomas originating in the intramuscular fat tissue and showing tendency of local recurrence in 1946.’ Greenberg et al classified these into two types (intermuscular or intramuscular) in 1963.3 The intermuscular type arises from the intermuscular fascial septa and invades the surrounding muscle layer across the fascial septa; the intramuscular type originates between the muscle fibers within the muscle bundles themselves and infiltrates adjacent muscles. Of these two types, the intermuscular type is more common and readily excised. Recent data are listed in Table l.‘-14In addition to these, Kindblom et al reported 46 cases of infiltrating lipoma, 34 of which were the intramuscular type. The tumors usually involve large muscles of extremities, especially the thigh and upper arm, and arise in all ages, but mainly adults in the 4th to 6th decades. Kindblom reported that tumors were more common in men than in women (male-female ratio, 27:19),” but the male to female ratio is 1:l in Table 1. Because most tumors are slow-growing and painless and often become apparent only with muscle contraction, surgical intervention is usually postponed until mass is sufficient to induce deformity, swelling, and pain. Winkler et al reviewed four pediatric cases of infiltrating lipomas with adequate histological documentation.14 Including the case reported therein, two of five cases were found to have mass on the forearm or back dating since birth, but ages at surgical exploration were 11 years in both cases. The present patient may be the youngest case of intramuscular lipoma, diagnosed at surgical exploration in the infantile period. Although differential diagnosis of a infiltrating lipoma includes various type of soft tissue tumors, consideration is usually limited to the typical lipoma, angiolipoma, and liposarcoma when size, location, consistency, and clinical course are assessed. On JournalofPediatric
Surgery, Vol26, No 2 (February), 1991: pp 230-232
Fig 1. Representative CT scan before operation. Note that the left gluteal muscle is replaced by the homogeneous low-density mass. Layered structure of the affected gluteal muscles can be observed.
microscopic examination, simple lipoma is composed of lipocytes with varying amounts of fibrous tissue and circumscribed by a delicate fibrous capsule. Infiltrating lipoma is also composed of mature lipocytes, but they infiltrate muscle in a diffuse manner without a few changes of striated muscle fibers. Cautions are necessary in diagnosis of well-differentiated liposarcoma, typically showing lipoblasts or cells with atypical nuclei. However, some cases of well-differentiated liposarcomas can be shown only by serial sections. Infiltrating angiolipoma is characterized by a striking predominance of blood vessels and a greater amount of connective tissue mixed with mature adipose tissue. A sonogram is effective to elucidate the echogenic nature of mass suggestive of adipose tissue, but often fails to delineate the exact outline of the tumor and its relationship to the surrounding muscle layer. CT is a useful diagnostic tool in the evaluation of these tumors based on differences in tumor density.16 Infiltrating lipomas usually appear as homogeneous fatdensity masses with well-defined margins and/or internal septations in the muscle layers in computed
Fig 3. Representative CT scan 6 months after operation. Almost the same level as in Fig 1. There seems to be no change in the nature of the tumor before and after operation. Size of the tumor was slightly expanded.
tomography. However, CT imaging of the tumor in the present patient was atypical in the sense that the fatty density component was homogeneously mixed with muscle bundles. MRI is a newly establi s?ed technique of imaging
6
i
Fig 2. Hematoxylin and eosin stain of biopsy specimen. The tumor consists of mature lipocytes penetrating into striated muscles in a diffuse manner. Note the complete absence of cellular etypism. (Original magnification x 144)
Fig 4. (A) Representative MRI scan of the tumor 6 months after operation (axial scan). Same level as in Fig 3. The tumor is represented as a homogeneous high-intensity mass and distinguished from the surrounding muscle layer. (6) Coronal scan of the tumor. Note that roughly half the gluteal muscles are involved.
232
KUBOTA ET AL
Table 1. Infiltrating Lipomas in the Literature Age at Studv
Sex
Diagnosis (vr)
Site
Size (cm)
Adir et al4
M
11
Forearm (L)
Hoffman et al*
F
42
Leg (R)
22 x 18 x 11
Regan et al2
M
8
Leg (R) Leg and foot
6X6
Osthuizen et ale
M
5th decade
Dempster’
M F
4mo 46
Gold et ala Greenberg et al3
F
0 x 4.5 x 3.5
Leg (L) Leg (L)
18
45
Forearm (R)
6x6~4
F
50
Thigh (R)
13.5 x 10 x 5.5
F
67
Thigh (R)
7X7X3
M
66
Thigh (L)
F
73
Thigh (L)
M
38
Leg (R)
20x4~6
M F
69
Leg (L) Upper arm
3 x 3.5 x 3.5
M F
48 59
Thigh (R)
13x7~6
Forearm (R)
3 x 1.5 x 1.0
M
43
Thigh (R)
45 x 25 x 13
M
58
Thigh (L)
18 x 12 x 4
Fetell et al”
F
12
Gastrocnemius (R)
Benhoff et alI2
M
11
Submandibular (L)
Austin et al”
F M
56 37
Thigh
12x9x6
Thigh
22 x 8.5 x 6.5
F
69
Thigh
10.5 x 10 x 5.5
F
10
Back
3x
Davis et al9 Dionne et al”
Winkler et al”
66
17X11X4
3x5
10
Abbreviation: L, left; R, right.
without radiation exposure. The usefulness of this technique is now widely appreciated. It was found that MRI of the tumor was effective in the evaluation of this patient. Fat tissue mixed with striated muscles appeared as higher intensity area than the surrounding muscle layer. Furthermore, the coronal view is useful in evaluation of exact anatomical relationship of the tumor to the surrounding tissue. Complete excision is the treatment of choice. Reportedly, the recurrence rate varied from 3%” to 62.5%,10 probably depending on the completeness of
the excision. However, in the present patient complete excision was avoided because of the possible occurrence of disturbances in the gate and physical development. Therefore, careful follow-up over the patient’s lifetime is necessary. We found that both CT and MRI had good resolution in imaging of the infiltrating lipoma in this patient. However, MRI is a more suitable diagnostic modality than CT, in the sense that multiplanar sections of the tumor are available and the unfavorable effect of radiation on the growing tissue can be eliminated.
REFERENCES 1. Behrend M: Intermuscular lipoma-report of three cases. Am J Surg 7:857-860,1929 2. Regan JM, Bikle WI-I, Broders AC: Infiltrating benign lipomas of extremities. West J Surg 54:87-93,1946 3. Greenberg SD, Isensee C, Gonzalez-Angulo A, et al: Infiltrating lipoma of the thigh. Am J Clin Path01 39:66-72,1963 4. Adir FE, Pack GT, Ferrior JH, et al: Lipomas. Am J Cancer 16:1104-1120,1932 5. Hoffmann HOE: Glomus and intramuscular lipoma: Reports of two cases. Mayo Clin Proc 16:13-16, 1941 6. Osthuizen SF, Barneison J: Two cases of lipomatosis involving bone. Br J Radio1 20:426-432,1947 7. Dempster WJ: Intermuscular lipomata. Br J Radio1 25:553555,1952 8. Gold AA, Oppenheim A: Deep intermuscular lipoma of an extremity. J Bone Joint Surg 36:146-1481954 9. Davis C Jr, Gruhn JG: Ginat lipoma of the thigh. Arch Surg 95:151-156, 1967
10. Dionne GP, Seemayer TA: Infiltrating lipoma and angiolipomas revisited. Cancer 33:732-738, 1974 11. Fete11 MR, Dully PE, Rowland LP: Infiltrating lipomas: A cause of monometric hypertrophy. Muscle Nerve 1:75-80, 1978 12. Benhoff DF, Wood JW: Infiltrating lipomata of the head and neck. Laryngoscope 88:839-848,1978 13. Austin MR, Mack GR, Townsend CM, et al: Infiltrating (intramuscular) lipomas and angiolipomas. A clinicopathological study of six cases. Arch Surg 115:281-284,198O 14. Winkler M, Petrelle N, Cohen A: Pediatric infiltrating lipomas: Case report and review of the literature. J Surg Oncol 35:59-62,1987 15. Kindblom LG, Angervall L, Stener B, et al: Intermuscular and intramuscular lipomas and hibernomas: A clinical roentgenologic, histologic and prognostic study of 46 cases. Cancer 33:754762,1974 16. Varma DGK, Muchmore JH, Mizushima A: Computed tomography of infiltrating benign lipoma. J Comput Assist Tomogr 11:45-49,1987
