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J Vet Clin 2023; 40(2): 147-151

https://doi.org/10.17555/jvc.2023.40.2.147

Published online April 30, 2023

Infiltrative Lipoma Invading the Anal Sac in a Dog: A Rare Case Report

Junyoung Kim1,2 , Dai Jung Chung1 , Jihye Choi2 , Junghee Yoon2,*

1N Animal Medical Center, Seoul 02732, Korea
2College of Veterinary Medicine and the Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea

Correspondence to:*heeyoon@snu.ac.kr

Received: February 16, 2023; Revised: March 13, 2023; Accepted: March 20, 2023

Copyright © The Korean Society of Veterinary Clinics.

A 6-year-old female Chihuahua was presented to the Animal Medical Center for surgical resection of a perineal mass that had recently increased in size. Ultrasonography revealed a large, homogeneous fatty mass with irregular margins between the surrounding muscle layers due to infiltrating fatty tissues. Cytological findings from fine-needle aspirates revealed numerous sheets and clusters of adipocytes, which was consistent with the fatty mass. Based on ultrasonographic and cytological findings, an infiltrative lipoma was suspected. During the surgery, the perineal mass was found to be non-encapsulated, irregularly marginated, and extensively distributed into the surrounding muscles. The mass extended inside the pelvic cavity and left anal sac. The perineal mass was surgically removed and submitted for histopathologic examination. Histopathology confirmed that the mass was an infiltrative lipoma invading into the anal sac and surrounding muscles. The present report was an unusual presentation of infiltrative lipoma that invaded the anal sac in the perineum.

Keywords: infiltrative lipoma, invasive, dog, radiography, ultrasound

Infiltrative lipomas are uncommon mesenchymal neoplasms characterized by highly differentiated adipocytes infiltrating the surrounding tissues (2,5,6,8). These tumors are derived from adipocytes in the subcutaneous tissue or from lipomas, and are classified as benign tumors because they rarely metastasize to distant organs (2,5,7-9). However, infiltrative lipomas are more invasive compared to other lipomas and have been reported to invade the adjacent tissues, such as muscles, connective tissues, bones, and rarely peripheral nerves and/or the spinal cord (2,5-9). Since the boundary between an infiltrative lipoma and normal tissue is difficult to define, the reported rate of recurrence after aggressive surgical resection ranges between 36-50% (3,5,8,9). Infiltrative lipomas typically occur in the thoracic wall and the extremities. However, they may also originate from the muscles of the head and neck region (1,8). In addition, the growth rate of infiltrative lipomas has been reported to be considerably more compared to other types of lipomas. Due to all the above-mentioned reasons, adjunctive chemotherapy and radiotherapy are recommended after surgical resection of the tumor (5,8). Herein, we describe an unusual presentation of infiltrative lipoma in a dog that invaded the anal sac.

A 6-year-old female Chihuahua weighing 3.2 kg was referred to the N Animal Medical Center for surgical resection of a perineal mass that had recently increased in size. The regional doctor considered the mass to be a perineal hernia. Physical examination revealed a large, soft, painless mass in the perineal region with swelling around the left side of the anus. No abnormalities were detected in the palpable lymph nodes. Blood profile showed unremarkable results except mildly increased glucose level (152 mg/dL; reference range: 75-128 mg/dL). Radiography demonstrated a large, inhomogeneous, fat-to-soft tissue opacity mass with swelling in the perineal region (Fig. 1). No other abnormalities were found on the radiographs. To further identify the characteristics of the perineal mass, ultrasonography was performed. Ultrasonography revealed a homogeneous hyperechoic fatty mass with no blood signal along with a combination of well- and ill-defined irregular margins (Fig. 2). Furthermore, in some perineal regions where fatty masses encountered the muscle layers, fine linear hyperechoic striations were found within the surrounding muscle, which were suggestive of infiltration by fatty tissues (Fig. 2). There was no evidence of metastasis to the thorax and abdomen on radiography and ultrasonography. Ultrasonography-guided fine-needle aspiration of the perineal mass was performed. Cytological findings revealed numerous sheets and clusters of adipocytes, which was consistent with a fatty mass. Based on radiography, ultrasonography, and cytology findings, the perineal mass was considered an adipose tumor and not a common perineal hernia containing abdominal organs. Among adipose tumors, infiltrative lipoma was considered the first differential diagnosis rather than simple lipoma or liposarcoma due to the ultrasonographic characteristics of the mass which showed no evidence of metastasis. Although computed tomography (CT) was recommended to identify the extent of adjacent tissue invasion by the fatty mass and to confirm no evidence of metastasis, surgery was immediately performed without CT at the request of the pet’s owner. During the surgery, the non-encapsulated and irregularly marginated fatty mass was found to be infiltrating into the surrounding muscle layers, inside the pelvic cavity, and in the left anal sac. Extensive resection of the mass including the left anal sac was performed (Fig. 3), and the resected specimen was sent for histopathological examination. . Histopathological examination revealed an infiltrative lipoma invading the left anal sac and the surrounding muscle layers (Fig. 4).

Figure 1.Right lateral (A) and ventrodorsal (B) radiographs showing a large, inhomogeneous, fat to soft tissue opacity mass with swelling in the perineal region.

Figure 2.The perineal mass showing homogenous, echogenic fatty tissues with coarse internal echotexture and irregular margination on ultrasonography (asterisks). Additionally, in some regions where fatty mass infiltrated the muscle layers, fine linear, hyperechoic striations were seen in the surrounding muscles (open arrows).

Figure 3.Gross appearance of the perineal mass during surgery. An extensive, non-encapsulated fatty mass is evident in the perineal region which extended to the left anal sac (B, asterisk), and was attached to external anal sphincter, and pelvic diaphragm muscles in the pelvic cavity (A, B).

Figure 4.Photomicrograph of the excised tissue specimen showing well-differentiated fat cells characterized by large clear vacuoles replacing the cytoplasm with eccentrically located nucleus. Fat cells infiltrated into the tissues were found in the atrophied muscles (A) and hepatoid gland around the mass (B). Hematoxylin and Eosin staining ×200.

In the present case, an extensive lesion in the perineal region was diagnosed as an infiltrative lipoma invading the left anal sac on the basis of radiology, ultrasonography, cytological and histopathological findings. This was an unusual presentation of canine infiltrative lipoma. To the best of our knowledge, infiltrative lipomas in the perianal region have been reported in only two other dogs till date, and are very rare (2). Moreover, ours is the first report in veterinary medicine to present a case of infiltrative lipoma invading the anal sac.

The current World Health Organization (WHO) classification of mesenchymal skin and soft tissue tumors in domestic animals recognizes three benign forms of adipose tissue tumors (lipomas, infiltrative lipomas, and angiolipomas), and one malignant form (liposarcoma) (6,11). Lipomas comprise well-differentiated lipocytes that can be difficult to distinguish from normal adipose tissue unless there is a fibrous component or a capsule (13). Infiltrative lipomas are locally invasive and infiltrate the surrounding normal muscle and fibrous tissue, but do not metastasize (2,5-8). Angiolipoma is another uncommon variant of lipoma, which is characterized by the presence of small, well-differentiated blood vessels interspersed in mature adipose tissue. Angiolipomas can be further subclassified as infiltrative or non-infiltrative (6,11). Liposarcomas are uncommon malignant neoplasms in dogs that are locally invasive. These neoplasms consist of malignant lipoblasts and mesenchymal tissue, and metastasize to the liver, lung, and bones (4,7). Cytological and histopathological examinations should be performed to differentiate between these adipose tumors. Liposarcomas are readily distinguishable from lipomas cytologically and histologically. However, infiltrative lipomas cannot be diagnosed accurately on the basis of either aspiration cytology or biopsy alone because the cellular and histological features of simple lipomas and infiltrative lipomas can be similar (7,9,11,12). A biopsy sample that does not include adjacent normal tissue will lead to an erroneous diagnosis of simple lipoma (2,9). It is important to differentiate between lipomas and infiltrative lipomas because the reported local recurrence rate following surgical excision of infiltrative lipomas ranges between 36-50% (3,5,8,9).

Several studies have described the characteristics of diagnostic imaging of adipose tumors (1,3,4,6,7,9,13). On ultrasonography, canine lipomas typically show uniform hyper echogenicity with coarse internal echotexture, sharp edges, and a thin hyperechoic capsule (3,7,10,13). Liposarcomas appear as heterogeneous masses consisting of multiple echogenic lines, and hyperechogenic or hypoechogenic nodules, along with increased vascularity and invasion into surrounding structures (7). On CT, lipomas appear as round to oval-shaped, well-marginated, fat-attenuating lesions with no contrast enhancement (7,11). On the other hand, infiltrative lipomas appear as homogeneous, fat-attenuating masses. However, unlike lipomas, they are most commonly characterized by an irregular shape with variable degrees of muscle infiltration, and hyperattenuating linear components relative to the surrounding fat (3,7,9,11). In addition, the demarcation of tumoral margins in infiltrative lipomas can be variable. They may be well-defined, ill-defined, or mixed (9). Conversely, liposarcomas can be represented exclusively as contrast-enhanced, heterogeneous lesions with soft tissue-attenuating components, and a multinodular appearance. Regional lymphadenopathy and amorphous mineralization are also observed in association with liposarcomas (4,7,11).

There is paucity of data on ultrasonographic characteristics of infiltrative lipomas. However, on the basis of previously mentioned CT imaging features of adipose tumor types, we believe that tumor definition and shape could be the most useful parameters for differentiating lipomas from infiltrative lipomas on ultrasonography as well. Although CT examination could not be performed in this case, infiltrative lipoma was considered the first differential diagnosis because the perineal mass showed irregular margins with invasion into the adjacent muscle layer by fat infiltration on ultrasonography. Since the site of occurrence of the tumor in the present case was an uncommon location for infiltrative lipoma, and the mass showed an inhomogeneous soft tissue opacity rather than fat opacity on radiographs, ultrasonography played a decisive role in the diagnosis. In addition, it was possible to predict extensive resection prior to surgery. Moreover, the possibility of recurrence in future could also be predicted. As general, it has been known that performing CT scans of patients with infiltrative lipomas would be helpful in surgical and radiation therapy planning to determine the extent of infiltration (6,9,11). Therefore, CT is a useful modality for adequate assessment of the extent of adipose masses, and should be considered before surgery or irradiation if physical examination or other diagnostic processes cannot determine whether the adipose mass is infiltrative or non-infiltrative (6). However, this case report suggests that if performing CT is difficult, ultrasonography may provide valuable information to help differentiate adipose tumors. Ultrasonography may be particularly useful in veterinary clinics because fatty tumors are often located superficially, commonly in the subcutaneous region or muscle tissues (1,4,7,8,12,13).

The present report describes a rare case of canine infiltrative lipoma invading the anal sac that was diagnosed by ultrasound and cytology, followed by surgical histopathology. Ultrasound examinations of more infiltrative lipomas in dogs would be helpful in determining its clinical relevance and for listing differential diagnoses of adipose tumors.

  1. Agut A, Anson A, Navarro A, Murciano J, Soler M, Belda E, et al. Imaging diagnosis-infiltrative lipoma causing spinal cord and lumbar nerve root compression in a dog. Vet Radiol Ultrasound 2013; 54: 381-383.
    Pubmed CrossRef
  2. Bergman PJ, Withrow SJ, Straw RC, Powers BE. Infiltrative lipoma in dogs: 16 cases (1981-1992). J Am Vet Med Assoc 1994; 205: 322-324.
  3. Case JB, MacPhail CM, Withrow SJ. Anatomic distribution and clinical findings of intermuscular lipomas in 17 dogs (2005-2010). J Am Anim Hosp Assoc 2012; 48: 245-249.
    Pubmed CrossRef
  4. Fuerst JA, Reichle JK, Szabo D, Cohen EB, Biller DS, Goggin JM, et al. Computed tomographic findings in 24 dogs with liposarcoma. Vet Radiol Ultrasound 2017; 58: 23-28.
    Pubmed CrossRef
  5. Kimura S, Yamazaki M, Tomohisa M, Mori T, Yanai T, Maeda S, et al. Infiltrative lipoma causing vertebral deformation and spinal cord compression in a dog. J Vet Med Sci 2018; 80: 1901-1904.
    Pubmed KoreaMed CrossRef
  6. Kurihara M, Bahr RJ, Green R. Liver enzyme elevation caused by a compression of infiltrative lipoma in a dog. Int J Vet Sci Med 2018; 6: 127-129.
    Pubmed KoreaMed CrossRef
  7. Lee NS, Kim JY, Na ES, Kim ME, Lee HY, Choi MH, et al. Diagnostic imaging of lipoma in the retroperitoneum and pelvic cavity in a dog. J Vet Clin 2010; 27: 88-92.
  8. McEntee MC, Page RL, Mauldin GN, Thrall DE. Results of irradiation of infiltrative lipoma in 13 dogs. Vet Radiol Ultrasound 2000; 41: 554-556.
    Pubmed CrossRef
  9. McEntee MC, Thrall DE. Computed tomographic imaging of infiltrative lipoma in 22 dogs. Vet Radiol Ultrasound 2001; 42: 221-225.
    Pubmed CrossRef
  10. Penninck P, d’Anjou MA. Atlas of small animal ultrasonography. 2nd ed. Hoboken: John Wiley & Sons Inc. 2008: 497-504.
  11. Spoldi E, Schwarz T, Sabattini S, Vignoli M, Cancedda S, Rossi F. Comparisons among computed tomographic features of adipose masses in dogs and cats. Vet Radiol Ultrasound 2017; 58: 29-37.
    Pubmed CrossRef
  12. Thomson MJ, Withrow SJ, Dernell WS, Powers BE. Intermuscular lipomas of the thigh region in dogs: 11 cases. J Am Anim Hosp Assoc 1999; 35: 165-167.
    Pubmed CrossRef
  13. Volta A, Bonazzi M, Gnudi G, Gazzola M, Bertoni G. Ultrasonographic features of canine lipomas. Vet Radiol Ultrasound 2006; 47: 589-591.
    Pubmed CrossRef

Article

Case Report

J Vet Clin 2023; 40(2): 147-151

Published online April 30, 2023 https://doi.org/10.17555/jvc.2023.40.2.147

Copyright © The Korean Society of Veterinary Clinics.

Infiltrative Lipoma Invading the Anal Sac in a Dog: A Rare Case Report

Junyoung Kim1,2 , Dai Jung Chung1 , Jihye Choi2 , Junghee Yoon2,*

1N Animal Medical Center, Seoul 02732, Korea
2College of Veterinary Medicine and the Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea

Correspondence to:*heeyoon@snu.ac.kr

Received: February 16, 2023; Revised: March 13, 2023; Accepted: March 20, 2023

This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A 6-year-old female Chihuahua was presented to the Animal Medical Center for surgical resection of a perineal mass that had recently increased in size. Ultrasonography revealed a large, homogeneous fatty mass with irregular margins between the surrounding muscle layers due to infiltrating fatty tissues. Cytological findings from fine-needle aspirates revealed numerous sheets and clusters of adipocytes, which was consistent with the fatty mass. Based on ultrasonographic and cytological findings, an infiltrative lipoma was suspected. During the surgery, the perineal mass was found to be non-encapsulated, irregularly marginated, and extensively distributed into the surrounding muscles. The mass extended inside the pelvic cavity and left anal sac. The perineal mass was surgically removed and submitted for histopathologic examination. Histopathology confirmed that the mass was an infiltrative lipoma invading into the anal sac and surrounding muscles. The present report was an unusual presentation of infiltrative lipoma that invaded the anal sac in the perineum.

Keywords: infiltrative lipoma, invasive, dog, radiography, ultrasound

Introduction

Infiltrative lipomas are uncommon mesenchymal neoplasms characterized by highly differentiated adipocytes infiltrating the surrounding tissues (2,5,6,8). These tumors are derived from adipocytes in the subcutaneous tissue or from lipomas, and are classified as benign tumors because they rarely metastasize to distant organs (2,5,7-9). However, infiltrative lipomas are more invasive compared to other lipomas and have been reported to invade the adjacent tissues, such as muscles, connective tissues, bones, and rarely peripheral nerves and/or the spinal cord (2,5-9). Since the boundary between an infiltrative lipoma and normal tissue is difficult to define, the reported rate of recurrence after aggressive surgical resection ranges between 36-50% (3,5,8,9). Infiltrative lipomas typically occur in the thoracic wall and the extremities. However, they may also originate from the muscles of the head and neck region (1,8). In addition, the growth rate of infiltrative lipomas has been reported to be considerably more compared to other types of lipomas. Due to all the above-mentioned reasons, adjunctive chemotherapy and radiotherapy are recommended after surgical resection of the tumor (5,8). Herein, we describe an unusual presentation of infiltrative lipoma in a dog that invaded the anal sac.

Case Report

A 6-year-old female Chihuahua weighing 3.2 kg was referred to the N Animal Medical Center for surgical resection of a perineal mass that had recently increased in size. The regional doctor considered the mass to be a perineal hernia. Physical examination revealed a large, soft, painless mass in the perineal region with swelling around the left side of the anus. No abnormalities were detected in the palpable lymph nodes. Blood profile showed unremarkable results except mildly increased glucose level (152 mg/dL; reference range: 75-128 mg/dL). Radiography demonstrated a large, inhomogeneous, fat-to-soft tissue opacity mass with swelling in the perineal region (Fig. 1). No other abnormalities were found on the radiographs. To further identify the characteristics of the perineal mass, ultrasonography was performed. Ultrasonography revealed a homogeneous hyperechoic fatty mass with no blood signal along with a combination of well- and ill-defined irregular margins (Fig. 2). Furthermore, in some perineal regions where fatty masses encountered the muscle layers, fine linear hyperechoic striations were found within the surrounding muscle, which were suggestive of infiltration by fatty tissues (Fig. 2). There was no evidence of metastasis to the thorax and abdomen on radiography and ultrasonography. Ultrasonography-guided fine-needle aspiration of the perineal mass was performed. Cytological findings revealed numerous sheets and clusters of adipocytes, which was consistent with a fatty mass. Based on radiography, ultrasonography, and cytology findings, the perineal mass was considered an adipose tumor and not a common perineal hernia containing abdominal organs. Among adipose tumors, infiltrative lipoma was considered the first differential diagnosis rather than simple lipoma or liposarcoma due to the ultrasonographic characteristics of the mass which showed no evidence of metastasis. Although computed tomography (CT) was recommended to identify the extent of adjacent tissue invasion by the fatty mass and to confirm no evidence of metastasis, surgery was immediately performed without CT at the request of the pet’s owner. During the surgery, the non-encapsulated and irregularly marginated fatty mass was found to be infiltrating into the surrounding muscle layers, inside the pelvic cavity, and in the left anal sac. Extensive resection of the mass including the left anal sac was performed (Fig. 3), and the resected specimen was sent for histopathological examination. . Histopathological examination revealed an infiltrative lipoma invading the left anal sac and the surrounding muscle layers (Fig. 4).

Figure 1. Right lateral (A) and ventrodorsal (B) radiographs showing a large, inhomogeneous, fat to soft tissue opacity mass with swelling in the perineal region.

Figure 2. The perineal mass showing homogenous, echogenic fatty tissues with coarse internal echotexture and irregular margination on ultrasonography (asterisks). Additionally, in some regions where fatty mass infiltrated the muscle layers, fine linear, hyperechoic striations were seen in the surrounding muscles (open arrows).

Figure 3. Gross appearance of the perineal mass during surgery. An extensive, non-encapsulated fatty mass is evident in the perineal region which extended to the left anal sac (B, asterisk), and was attached to external anal sphincter, and pelvic diaphragm muscles in the pelvic cavity (A, B).

Figure 4. Photomicrograph of the excised tissue specimen showing well-differentiated fat cells characterized by large clear vacuoles replacing the cytoplasm with eccentrically located nucleus. Fat cells infiltrated into the tissues were found in the atrophied muscles (A) and hepatoid gland around the mass (B). Hematoxylin and Eosin staining ×200.

Discussion

In the present case, an extensive lesion in the perineal region was diagnosed as an infiltrative lipoma invading the left anal sac on the basis of radiology, ultrasonography, cytological and histopathological findings. This was an unusual presentation of canine infiltrative lipoma. To the best of our knowledge, infiltrative lipomas in the perianal region have been reported in only two other dogs till date, and are very rare (2). Moreover, ours is the first report in veterinary medicine to present a case of infiltrative lipoma invading the anal sac.

The current World Health Organization (WHO) classification of mesenchymal skin and soft tissue tumors in domestic animals recognizes three benign forms of adipose tissue tumors (lipomas, infiltrative lipomas, and angiolipomas), and one malignant form (liposarcoma) (6,11). Lipomas comprise well-differentiated lipocytes that can be difficult to distinguish from normal adipose tissue unless there is a fibrous component or a capsule (13). Infiltrative lipomas are locally invasive and infiltrate the surrounding normal muscle and fibrous tissue, but do not metastasize (2,5-8). Angiolipoma is another uncommon variant of lipoma, which is characterized by the presence of small, well-differentiated blood vessels interspersed in mature adipose tissue. Angiolipomas can be further subclassified as infiltrative or non-infiltrative (6,11). Liposarcomas are uncommon malignant neoplasms in dogs that are locally invasive. These neoplasms consist of malignant lipoblasts and mesenchymal tissue, and metastasize to the liver, lung, and bones (4,7). Cytological and histopathological examinations should be performed to differentiate between these adipose tumors. Liposarcomas are readily distinguishable from lipomas cytologically and histologically. However, infiltrative lipomas cannot be diagnosed accurately on the basis of either aspiration cytology or biopsy alone because the cellular and histological features of simple lipomas and infiltrative lipomas can be similar (7,9,11,12). A biopsy sample that does not include adjacent normal tissue will lead to an erroneous diagnosis of simple lipoma (2,9). It is important to differentiate between lipomas and infiltrative lipomas because the reported local recurrence rate following surgical excision of infiltrative lipomas ranges between 36-50% (3,5,8,9).

Several studies have described the characteristics of diagnostic imaging of adipose tumors (1,3,4,6,7,9,13). On ultrasonography, canine lipomas typically show uniform hyper echogenicity with coarse internal echotexture, sharp edges, and a thin hyperechoic capsule (3,7,10,13). Liposarcomas appear as heterogeneous masses consisting of multiple echogenic lines, and hyperechogenic or hypoechogenic nodules, along with increased vascularity and invasion into surrounding structures (7). On CT, lipomas appear as round to oval-shaped, well-marginated, fat-attenuating lesions with no contrast enhancement (7,11). On the other hand, infiltrative lipomas appear as homogeneous, fat-attenuating masses. However, unlike lipomas, they are most commonly characterized by an irregular shape with variable degrees of muscle infiltration, and hyperattenuating linear components relative to the surrounding fat (3,7,9,11). In addition, the demarcation of tumoral margins in infiltrative lipomas can be variable. They may be well-defined, ill-defined, or mixed (9). Conversely, liposarcomas can be represented exclusively as contrast-enhanced, heterogeneous lesions with soft tissue-attenuating components, and a multinodular appearance. Regional lymphadenopathy and amorphous mineralization are also observed in association with liposarcomas (4,7,11).

There is paucity of data on ultrasonographic characteristics of infiltrative lipomas. However, on the basis of previously mentioned CT imaging features of adipose tumor types, we believe that tumor definition and shape could be the most useful parameters for differentiating lipomas from infiltrative lipomas on ultrasonography as well. Although CT examination could not be performed in this case, infiltrative lipoma was considered the first differential diagnosis because the perineal mass showed irregular margins with invasion into the adjacent muscle layer by fat infiltration on ultrasonography. Since the site of occurrence of the tumor in the present case was an uncommon location for infiltrative lipoma, and the mass showed an inhomogeneous soft tissue opacity rather than fat opacity on radiographs, ultrasonography played a decisive role in the diagnosis. In addition, it was possible to predict extensive resection prior to surgery. Moreover, the possibility of recurrence in future could also be predicted. As general, it has been known that performing CT scans of patients with infiltrative lipomas would be helpful in surgical and radiation therapy planning to determine the extent of infiltration (6,9,11). Therefore, CT is a useful modality for adequate assessment of the extent of adipose masses, and should be considered before surgery or irradiation if physical examination or other diagnostic processes cannot determine whether the adipose mass is infiltrative or non-infiltrative (6). However, this case report suggests that if performing CT is difficult, ultrasonography may provide valuable information to help differentiate adipose tumors. Ultrasonography may be particularly useful in veterinary clinics because fatty tumors are often located superficially, commonly in the subcutaneous region or muscle tissues (1,4,7,8,12,13).

Conclusions

The present report describes a rare case of canine infiltrative lipoma invading the anal sac that was diagnosed by ultrasound and cytology, followed by surgical histopathology. Ultrasound examinations of more infiltrative lipomas in dogs would be helpful in determining its clinical relevance and for listing differential diagnoses of adipose tumors.

Source of Funding

No funding was received for this study.

Conflicts of Interest

The authors have no conflicting interests.

Fig 1.

Figure 1.Right lateral (A) and ventrodorsal (B) radiographs showing a large, inhomogeneous, fat to soft tissue opacity mass with swelling in the perineal region.
Journal of Veterinary Clinics 2023; 40: 147-151https://doi.org/10.17555/jvc.2023.40.2.147

Fig 2.

Figure 2.The perineal mass showing homogenous, echogenic fatty tissues with coarse internal echotexture and irregular margination on ultrasonography (asterisks). Additionally, in some regions where fatty mass infiltrated the muscle layers, fine linear, hyperechoic striations were seen in the surrounding muscles (open arrows).
Journal of Veterinary Clinics 2023; 40: 147-151https://doi.org/10.17555/jvc.2023.40.2.147

Fig 3.

Figure 3.Gross appearance of the perineal mass during surgery. An extensive, non-encapsulated fatty mass is evident in the perineal region which extended to the left anal sac (B, asterisk), and was attached to external anal sphincter, and pelvic diaphragm muscles in the pelvic cavity (A, B).
Journal of Veterinary Clinics 2023; 40: 147-151https://doi.org/10.17555/jvc.2023.40.2.147

Fig 4.

Figure 4.Photomicrograph of the excised tissue specimen showing well-differentiated fat cells characterized by large clear vacuoles replacing the cytoplasm with eccentrically located nucleus. Fat cells infiltrated into the tissues were found in the atrophied muscles (A) and hepatoid gland around the mass (B). Hematoxylin and Eosin staining ×200.
Journal of Veterinary Clinics 2023; 40: 147-151https://doi.org/10.17555/jvc.2023.40.2.147

References

  1. Agut A, Anson A, Navarro A, Murciano J, Soler M, Belda E, et al. Imaging diagnosis-infiltrative lipoma causing spinal cord and lumbar nerve root compression in a dog. Vet Radiol Ultrasound 2013; 54: 381-383.
    Pubmed CrossRef
  2. Bergman PJ, Withrow SJ, Straw RC, Powers BE. Infiltrative lipoma in dogs: 16 cases (1981-1992). J Am Vet Med Assoc 1994; 205: 322-324.
  3. Case JB, MacPhail CM, Withrow SJ. Anatomic distribution and clinical findings of intermuscular lipomas in 17 dogs (2005-2010). J Am Anim Hosp Assoc 2012; 48: 245-249.
    Pubmed CrossRef
  4. Fuerst JA, Reichle JK, Szabo D, Cohen EB, Biller DS, Goggin JM, et al. Computed tomographic findings in 24 dogs with liposarcoma. Vet Radiol Ultrasound 2017; 58: 23-28.
    Pubmed CrossRef
  5. Kimura S, Yamazaki M, Tomohisa M, Mori T, Yanai T, Maeda S, et al. Infiltrative lipoma causing vertebral deformation and spinal cord compression in a dog. J Vet Med Sci 2018; 80: 1901-1904.
    Pubmed KoreaMed CrossRef
  6. Kurihara M, Bahr RJ, Green R. Liver enzyme elevation caused by a compression of infiltrative lipoma in a dog. Int J Vet Sci Med 2018; 6: 127-129.
    Pubmed KoreaMed CrossRef
  7. Lee NS, Kim JY, Na ES, Kim ME, Lee HY, Choi MH, et al. Diagnostic imaging of lipoma in the retroperitoneum and pelvic cavity in a dog. J Vet Clin 2010; 27: 88-92.
  8. McEntee MC, Page RL, Mauldin GN, Thrall DE. Results of irradiation of infiltrative lipoma in 13 dogs. Vet Radiol Ultrasound 2000; 41: 554-556.
    Pubmed CrossRef
  9. McEntee MC, Thrall DE. Computed tomographic imaging of infiltrative lipoma in 22 dogs. Vet Radiol Ultrasound 2001; 42: 221-225.
    Pubmed CrossRef
  10. Penninck P, d’Anjou MA. Atlas of small animal ultrasonography. 2nd ed. Hoboken: John Wiley & Sons Inc. 2008: 497-504.
  11. Spoldi E, Schwarz T, Sabattini S, Vignoli M, Cancedda S, Rossi F. Comparisons among computed tomographic features of adipose masses in dogs and cats. Vet Radiol Ultrasound 2017; 58: 29-37.
    Pubmed CrossRef
  12. Thomson MJ, Withrow SJ, Dernell WS, Powers BE. Intermuscular lipomas of the thigh region in dogs: 11 cases. J Am Anim Hosp Assoc 1999; 35: 165-167.
    Pubmed CrossRef
  13. Volta A, Bonazzi M, Gnudi G, Gazzola M, Bertoni G. Ultrasonographic features of canine lipomas. Vet Radiol Ultrasound 2006; 47: 589-591.
    Pubmed CrossRef

Vol.41 No.1 February 2024

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