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Intrathoracic histiocytic sarcoma in dogs
PAG E 4
A D VA N C E S
bone, subcutis, joints, liver, spleen, gastrointestinal tract, lung, brain, spinal cord, eye, and nasal cavity. Disseminated histiocytic sarcoma affects multiple organs, particularly the lung, spleen, bone marrow, liver, and lymph nodes. Histiocytic sarcoma is highly aggressive with a variable prognosis. The localized form exhibits a metastatic rate up to 91%. Median survival of 18 months is reported when the localized form is treated aggressively with surgery and adjuvant CCNU, while nonresectable or disseminated disease has a 29% response rate and median survival of 4 months when treated with CCNU. Bernese mountain dogs have a worse prognosis than other breeds. Reported median survival in Bernese mountain dogs is 30 days, with less than 10% survival at 4 months. Diagnostic imaging findings of canine histiocytic sarocomas in the lung include solitary masses, pulmonary nodules, and diffuse or focal interstitial patterns. In addition sternal, tracheobronchial, and cranial mediastinal lymphoadenopathy have been reported.
Objectives To investigate the most common intrathoracic presentation of histiocytic sarcoma in dogs.
Procedure Two observers independently reviewed thoracic imaging studies of 39 dogs with confirmed histiocytic sarcoma.
INTRATHORACIC HISTIOCYTIC SARCOMA IN DOGS Background Histiocytic sarcoma is a rare, round cell neoplasm in dogs that was first described in 1978. The neoplasm arises from dendritic antigen presenting cells or cells of the monocyte-macrophage line. Histiocytic sarcoma has a known familial relationship in Bernese mountain dogs, although Rottweilers, flat-coated retrievers, golden retrievers, and Labrador retrievers are also predisposed. For example, Bernese mountain dogs are 225 times more likely than most other breeds to develop histiocytic sarcoma, while Rottweilers are 26 times more likely. Histiocytic sarcoma in dogs can be localized and disseminated. Localized histiocytic sarcoma lesions occur in
Results The most common findings were intrathoracic lymphadenopathy, identified by the first and second observers in 82.1% and 87.2% of dogs, respectively, and pulmonary masses (74.4% and 82.1% of dogs). Right middle lung lobe masses were significantly more common than masses in any other lung lobe, with the majority having a ventral distribution. Sternal and tracheobroncial lymphadenopathy were significantly more common than cranial mediastinal lymphadenopathy. Interobserver agreement regarding distribution of lymphadenopathy and pulmonary masses was good. Other findings included pulmonary nodules, pleural effusion, and abnormal pulmonary patterns. In patients with computed tomographic examinations, the majority of masses were mildly to moderately enhancing and hetero-
A D VA N C E S
genous, poorly marginated, and bronchocentric.
Author Conclusion Lymphadenopathy and pulmonary masses are the most common intrathoracic findings in dogs with histiocytic sarcoma. The strong predilection for the ventral aspect of the right middle lung lobe may help to differentiate it from other types of neoplasia.
Inclusions Four figures, 42 references.
Editor Annotation Histiocytic sarcomas are a type of round cell neoplasm in dogs that arise from dendritic antigen-presenting cells of the monocyte-macrophage line. This is a highly aggressive neoplasm with a high metastatic rate and variable prognosis. Based on the results of this study, the most common intrathoracic findings with canine histiocytic sarcoma included pulmonary masses (more than 3 cm) and lymphadenopathy. Interestingly, more than half of all masses were in the right middle lung lobe. This is in contrast to other types of primary lung tumors, such as bronchogenic carcinoma, which have a predilection for the right caudal lung lobe. This may provide a distinguishing characteristic to help increase the suspicion of a histiocytic sarcoma. In addition, the majority of the pulmonary masses were distributed ventrally and peripherally. Sternal and tracheobronchial lymphadenopathy were also identified more commonly that cranial mediastinal lymphadenopathy. A limitation of this study is that neither a control population nor comparison population with other pulmonary neoplasms was included. A definitive conclusion that histiocytic sarcomas have a different appearance compared to other primary neoplasms, therefore, cannot be made. However, these findings can increase the suspicion of this type of tumor and may help to ultimately differentiate it from other types of pulmonary neoplasia. (SE) Tsai S, Sutherland-Smith J, Burgess K, et al. Imaging characteristics of intrathoracic histiocytic sarcoma in dogs. Vet Radiol Ultrasound 2012;53:21-27.
PAG E 5
A D VA N C E S
bone, subcutis, joints, liver, spleen, gastrointestinal tract, lung, brain, spinal cord, eye, and nasal cavity. Disseminated histiocytic sarcoma affects multiple organs, particularly the lung, spleen, bone marrow, liver, and lymph nodes. Histiocytic sarcoma is highly aggressive with a variable prognosis. The localized form exhibits a metastatic rate up to 91%. Median survival of 18 months is reported when the localized form is treated aggressively with surgery and adjuvant CCNU, while nonresectable or disseminated disease has a 29% response rate and median survival of 4 months when treated with CCNU. Bernese mountain dogs have a worse prognosis than other breeds. Reported median survival in Bernese mountain dogs is 30 days, with less than 10% survival at 4 months. Diagnostic imaging findings of canine histiocytic sarocomas in the lung include solitary masses, pulmonary nodules, and diffuse or focal interstitial patterns. In addition sternal, tracheobronchial, and cranial mediastinal lymphoadenopathy have been reported.
Objectives To investigate the most common intrathoracic presentation of histiocytic sarcoma in dogs.
Procedure Two observers independently reviewed thoracic imaging studies of 39 dogs with confirmed histiocytic sarcoma.
INTRATHORACIC HISTIOCYTIC SARCOMA IN DOGS Background Histiocytic sarcoma is a rare, round cell neoplasm in dogs that was first described in 1978. The neoplasm arises from dendritic antigen presenting cells or cells of the monocyte-macrophage line. Histiocytic sarcoma has a known familial relationship in Bernese mountain dogs, although Rottweilers, flat-coated retrievers, golden retrievers, and Labrador retrievers are also predisposed. For example, Bernese mountain dogs are 225 times more likely than most other breeds to develop histiocytic sarcoma, while Rottweilers are 26 times more likely. Histiocytic sarcoma in dogs can be localized and disseminated. Localized histiocytic sarcoma lesions occur in
Results The most common findings were intrathoracic lymphadenopathy, identified by the first and second observers in 82.1% and 87.2% of dogs, respectively, and pulmonary masses (74.4% and 82.1% of dogs). Right middle lung lobe masses were significantly more common than masses in any other lung lobe, with the majority having a ventral distribution. Sternal and tracheobroncial lymphadenopathy were significantly more common than cranial mediastinal lymphadenopathy. Interobserver agreement regarding distribution of lymphadenopathy and pulmonary masses was good. Other findings included pulmonary nodules, pleural effusion, and abnormal pulmonary patterns. In patients with computed tomographic examinations, the majority of masses were mildly to moderately enhancing and hetero-
A D VA N C E S
genous, poorly marginated, and bronchocentric.
Author Conclusion Lymphadenopathy and pulmonary masses are the most common intrathoracic findings in dogs with histiocytic sarcoma. The strong predilection for the ventral aspect of the right middle lung lobe may help to differentiate it from other types of neoplasia.
Inclusions Four figures, 42 references.
Editor Annotation Histiocytic sarcomas are a type of round cell neoplasm in dogs that arise from dendritic antigen-presenting cells of the monocyte-macrophage line. This is a highly aggressive neoplasm with a high metastatic rate and variable prognosis. Based on the results of this study, the most common intrathoracic findings with canine histiocytic sarcoma included pulmonary masses (more than 3 cm) and lymphadenopathy. Interestingly, more than half of all masses were in the right middle lung lobe. This is in contrast to other types of primary lung tumors, such as bronchogenic carcinoma, which have a predilection for the right caudal lung lobe. This may provide a distinguishing characteristic to help increase the suspicion of a histiocytic sarcoma. In addition, the majority of the pulmonary masses were distributed ventrally and peripherally. Sternal and tracheobronchial lymphadenopathy were also identified more commonly that cranial mediastinal lymphadenopathy. A limitation of this study is that neither a control population nor comparison population with other pulmonary neoplasms was included. A definitive conclusion that histiocytic sarcomas have a different appearance compared to other primary neoplasms, therefore, cannot be made. However, these findings can increase the suspicion of this type of tumor and may help to ultimately differentiate it from other types of pulmonary neoplasia. (SE) Tsai S, Sutherland-Smith J, Burgess K, et al. Imaging characteristics of intrathoracic histiocytic sarcoma in dogs. Vet Radiol Ultrasound 2012;53:21-27.
PAG E 5