Quiz: Mast Cell Tumors

The diagnosis was unclear because certain MCT granules do not stain well with Diff-Quik or other commercial aqueous Romanowsky stains.¹ Under these circumstances, in-house identification of MCTs can be difficult, with the cells being mistakenly identified as another round cell tumor (eg, histiocytoma).^2,3 

Overall, granularity can be affected by tumor differentiation, and thus poorly differentiated MCTs may have cells with a lower number of granules. This is not true for all MCTs, however. Fortunately, most MCT aspirates will stain with in-house stain kits, with one study also determining that the length of fixation did not appear to impact stain quality.⁴ In addition, no improvement in staining aspirates with Wright’s stain versus Diff-Quik was noted.⁴ However, the study involved only 17 tumors.

The diagnosis was unclear because certain MCT granules do not stain well with Diff-Quik or other commercial aqueous Romanowsky stains.¹ Under these circumstances, in-house identification of MCTs can be difficult, with the cells being mistakenly identified as another round cell tumor (eg, histiocytoma).^2,3 

Overall, granularity can be affected by tumor differentiation, and thus poorly differentiated MCTs may have cells with a lower number of granules. This is not true for all MCTs, however. Fortunately, most MCT aspirates will stain with in-house stain kits, with one study also determining that the length of fixation did not appear to impact stain quality.⁴ In addition, no improvement in staining aspirates with Wright’s stain versus Diff-Quik was noted.⁴ However, the study involved only 17 tumors.

The diagnosis was unclear because certain MCT granules do not stain well with Diff-Quik or other commercial aqueous Romanowsky stains.¹ Under these circumstances, in-house identification of MCTs can be difficult, with the cells being mistakenly identified as another round cell tumor (eg, histiocytoma).^2,3 

Overall, granularity can be affected by tumor differentiation, and thus poorly differentiated MCTs may have cells with a lower number of granules. This is not true for all MCTs, however. Fortunately, most MCT aspirates will stain with in-house stain kits, with one study also determining that the length of fixation did not appear to impact stain quality.⁴ In addition, no improvement in staining aspirates with Wright’s stain versus Diff-Quik was noted.⁴ However, the study involved only 17 tumors.

The diagnosis was unclear because certain MCT granules do not stain well with Diff-Quik or other commercial aqueous Romanowsky stains.¹ Under these circumstances, in-house identification of MCTs can be difficult, with the cells being mistakenly identified as another round cell tumor (eg, histiocytoma).^2,3 

Overall, granularity can be affected by tumor differentiation, and thus poorly differentiated MCTs may have cells with a lower number of granules. This is not true for all MCTs, however. Fortunately, most MCT aspirates will stain with in-house stain kits, with one study also determining that the length of fixation did not appear to impact stain quality.⁴ In addition, no improvement in staining aspirates with Wright’s stain versus Diff-Quik was noted.⁴ However, the study involved only 17 tumors.

Fine-needle aspiration (FNA) can be useful for preliminary diagnosis of canine cutaneous masses. This diagnostic technique can provide preliminary information as to whether the population of cells are representative of inflammation (eg, abscess, inflammatory nodule) or neoplasia. Round cell tumors especially can be fairly exfoliative, which can allow for a reasonably rewarding aspiration of MCTs.²  

One study has suggested that MCTs measuring >3 cm had a worse prognosis; thus, waiting until tumors are larger may affect prognosis.⁵ This may be secondary to the potential for the mass to become nonresectable with too much growth. 

Although this tumor could be benign (eg, a lipoma), brachycephalic breeds are overrepresented for MCTs; thus MCT should be ruled out as a differential.⁶ 

Performing excisional biopsy without knowledge of tumor type is generally discouraged. There are exceptions to the approach (eg, if the tumor size is too small for incisional biopsy). If histopathologic findings indicate the mass is malignant, scar revision will involve more extensive surgery than removal of the mass with appropriate margins at the first excision. For scar revisions, the scar is treated like the primary tumor; and for a MCT, this would include 2-cm lateral margins and 1 fascial plane deep.^7,8 It is also recommended to submit all resected tissue for histopathology, as biopsy samples may not be indicative of the tumor as a whole. Tumors are heterogeneous and submission of the entire tissue may yield additional information.⁹ When the cost of the pathologist’s report is built into the cost of surgery, owners are not required to decide whether to obtain this information (ie, as they may not full understand its value).  

Based on a history of no change in size for several months, this mass is unlikely an abscess; lancing the mass likely would not be diagnostic or otherwise beneficial to the patient and could hasten the spread of any neoplastic cells that may be present. 

Fine-needle aspiration (FNA) can be useful for preliminary diagnosis of canine cutaneous masses. This diagnostic technique can provide preliminary information as to whether the population of cells are representative of inflammation (eg, abscess, inflammatory nodule) or neoplasia. Round cell tumors especially can be fairly exfoliative, which can allow for a reasonably rewarding aspiration of MCTs.²  

One study has suggested that MCTs measuring >3 cm had a worse prognosis; thus, waiting until tumors are larger may affect prognosis.⁵ This may be secondary to the potential for the mass to become nonresectable with too much growth. 

Although this tumor could be benign (eg, a lipoma), brachycephalic breeds are overrepresented for MCTs; thus MCT should be ruled out as a differential.⁶ 

Performing excisional biopsy without knowledge of tumor type is generally discouraged. There are exceptions to the approach (eg, if the tumor size is too small for incisional biopsy). If histopathologic findings indicate the mass is malignant, scar revision will involve more extensive surgery than removal of the mass with appropriate margins at the first excision. For scar revisions, the scar is treated like the primary tumor; and for a MCT, this would include 2-cm lateral margins and 1 fascial plane deep.^7,8 It is also recommended to submit all resected tissue for histopathology, as biopsy samples may not be indicative of the tumor as a whole. Tumors are heterogeneous and submission of the entire tissue may yield additional information.⁹ When the cost of the pathologist’s report is built into the cost of surgery, owners are not required to decide whether to obtain this information (ie, as they may not full understand its value).  

Based on a history of no change in size for several months, this mass is unlikely an abscess; lancing the mass likely would not be diagnostic or otherwise beneficial to the patient and could hasten the spread of any neoplastic cells that may be present. 

Fine-needle aspiration (FNA) can be useful for preliminary diagnosis of canine cutaneous masses. This diagnostic technique can provide preliminary information as to whether the population of cells are representative of inflammation (eg, abscess, inflammatory nodule) or neoplasia. Round cell tumors especially can be fairly exfoliative, which can allow for a reasonably rewarding aspiration of MCTs.²  

One study has suggested that MCTs measuring >3 cm had a worse prognosis; thus, waiting until tumors are larger may affect prognosis.⁵ This may be secondary to the potential for the mass to become nonresectable with too much growth. 

Although this tumor could be benign (eg, a lipoma), brachycephalic breeds are overrepresented for MCTs; thus MCT should be ruled out as a differential.⁶ 

Performing excisional biopsy without knowledge of tumor type is generally discouraged. There are exceptions to the approach (eg, if the tumor size is too small for incisional biopsy). If histopathologic findings indicate the mass is malignant, scar revision will involve more extensive surgery than removal of the mass with appropriate margins at the first excision. For scar revisions, the scar is treated like the primary tumor; and for a MCT, this would include 2-cm lateral margins and 1 fascial plane deep.^7,8 It is also recommended to submit all resected tissue for histopathology, as biopsy samples may not be indicative of the tumor as a whole. Tumors are heterogeneous and submission of the entire tissue may yield additional information.⁹ When the cost of the pathologist’s report is built into the cost of surgery, owners are not required to decide whether to obtain this information (ie, as they may not full understand its value).  

Based on a history of no change in size for several months, this mass is unlikely an abscess; lancing the mass likely would not be diagnostic or otherwise beneficial to the patient and could hasten the spread of any neoplastic cells that may be present. 

Fine-needle aspiration (FNA) can be useful for preliminary diagnosis of canine cutaneous masses. This diagnostic technique can provide preliminary information as to whether the population of cells are representative of inflammation (eg, abscess, inflammatory nodule) or neoplasia. Round cell tumors especially can be fairly exfoliative, which can allow for a reasonably rewarding aspiration of MCTs.²  

One study has suggested that MCTs measuring >3 cm had a worse prognosis; thus, waiting until tumors are larger may affect prognosis.⁵ This may be secondary to the potential for the mass to become nonresectable with too much growth. 

Although this tumor could be benign (eg, a lipoma), brachycephalic breeds are overrepresented for MCTs; thus MCT should be ruled out as a differential.⁶ 

Performing excisional biopsy without knowledge of tumor type is generally discouraged. There are exceptions to the approach (eg, if the tumor size is too small for incisional biopsy). If histopathologic findings indicate the mass is malignant, scar revision will involve more extensive surgery than removal of the mass with appropriate margins at the first excision. For scar revisions, the scar is treated like the primary tumor; and for a MCT, this would include 2-cm lateral margins and 1 fascial plane deep.^7,8 It is also recommended to submit all resected tissue for histopathology, as biopsy samples may not be indicative of the tumor as a whole. Tumors are heterogeneous and submission of the entire tissue may yield additional information.⁹ When the cost of the pathologist’s report is built into the cost of surgery, owners are not required to decide whether to obtain this information (ie, as they may not full understand its value).  

Based on a history of no change in size for several months, this mass is unlikely an abscess; lancing the mass likely would not be diagnostic or otherwise beneficial to the patient and could hasten the spread of any neoplastic cells that may be present. 

Fine-needle aspiration (FNA) can be useful for preliminary diagnosis of canine cutaneous masses. This diagnostic technique can provide preliminary information as to whether the population of cells are representative of inflammation (eg, abscess, inflammatory nodule) or neoplasia. Round cell tumors especially can be fairly exfoliative, which can allow for a reasonably rewarding aspiration of MCTs.²  

One study has suggested that MCTs measuring >3 cm had a worse prognosis; thus, waiting until tumors are larger may affect prognosis.⁵ This may be secondary to the potential for the mass to become nonresectable with too much growth. 

Although this tumor could be benign (eg, a lipoma), brachycephalic breeds are overrepresented for MCTs; thus MCT should be ruled out as a differential.⁶ 

Performing excisional biopsy without knowledge of tumor type is generally discouraged. There are exceptions to the approach (eg, if the tumor size is too small for incisional biopsy). If histopathologic findings indicate the mass is malignant, scar revision will involve more extensive surgery than removal of the mass with appropriate margins at the first excision. For scar revisions, the scar is treated like the primary tumor; and for a MCT, this would include 2-cm lateral margins and 1 fascial plane deep.^7,8 It is also recommended to submit all resected tissue for histopathology, as biopsy samples may not be indicative of the tumor as a whole. Tumors are heterogeneous and submission of the entire tissue may yield additional information.⁹ When the cost of the pathologist’s report is built into the cost of surgery, owners are not required to decide whether to obtain this information (ie, as they may not full understand its value).  

Based on a history of no change in size for several months, this mass is unlikely an abscess; lancing the mass likely would not be diagnostic or otherwise beneficial to the patient and could hasten the spread of any neoplastic cells that may be present. 

Answers A, B, and E could be appropriate recommendations for this dog.

Most of the literature regarding adequate local control for canine MCTs has covered low-grade or Patnaik grades 1 and 2 tumors.⁷ Higher-grade tumors may require a more aggressive resection, but that remains unclear in the literature.¹⁰ Staging the tumor grade based on incisional biopsy before surgery can, therefore, be helpful for surgical planning. However, some owners may be unwilling to approve two separate procedures and would prefer removal of the mass in a single surgery. For this dog, removal following 2-cm lateral margins and 1 fascial plane deep would generally be sufficient, as this approach represents adequate resection of most MCTs. 

Excisional biopsy of this mass would be unlikely to attain complete margins and may make complete resection more difficult in the future, as the entire scar would be considered part of the field.^7,11 Neoadjuvant administration of prednisone before surgery can be useful in some cases but could also limit the ability to perform staging diagnostics; furthermore, the effect on biopsied tumor tissue remains unknown (ie, possibly alter mass appearance and change grade assigned by the pathologist).¹² 

Mast cells have histamine-containing granules that can cause an increase in gastric acid production when released, resulting in gastric ulceration in some patients with MCTs. Thus, for all patients with gross mast cell disease, administration of a medication that reduces gastric acid release, such as an H₂-blocker (eg, famotidine; also called H₂-receptor antagonist) and an antihistamine (eg, diphenhydramine) is recommended. Referral to a medical oncologist is recommended for all patients with evidence of neoplasia.^13,14

Answers A, B, and E could be appropriate recommendations for this dog.

Most of the literature regarding adequate local control for canine MCTs has covered low-grade or Patnaik grades 1 and 2 tumors.⁷ Higher-grade tumors may require a more aggressive resection, but that remains unclear in the literature.¹⁰ Staging the tumor grade based on incisional biopsy before surgery can, therefore, be helpful for surgical planning. However, some owners may be unwilling to approve two separate procedures and would prefer removal of the mass in a single surgery. For this dog, removal following 2-cm lateral margins and 1 fascial plane deep would generally be sufficient, as this approach represents adequate resection of most MCTs. 

Excisional biopsy of this mass would be unlikely to attain complete margins and may make complete resection more difficult in the future, as the entire scar would be considered part of the field.^7,11 Neoadjuvant administration of prednisone before surgery can be useful in some cases but could also limit the ability to perform staging diagnostics; furthermore, the effect on biopsied tumor tissue remains unknown (ie, possibly alter mass appearance and change grade assigned by the pathologist).¹² 

Mast cells have histamine-containing granules that can cause an increase in gastric acid production when released, resulting in gastric ulceration in some patients with MCTs. Thus, for all patients with gross mast cell disease, administration of a medication that reduces gastric acid release, such as an H₂-blocker (eg, famotidine; also called H₂-receptor antagonist) and an antihistamine (eg, diphenhydramine) is recommended. Referral to a medical oncologist is recommended for all patients with evidence of neoplasia.^13,14

Staging diagnostics should be completed for all grade II Patnaik MCTs. Appropriate staging should include FNA of mandibular and prescapular lymph nodes and abdominal ultrasonography, and in some cases FNA of the liver and spleen.^15-17 Tumor grade has been prognostic for end points (eg, survival, disease-free interval); and high-grade tumors, regardless of whether graded on the Patnaik or Kiupel scheme, have an increased rate of metastasis. Grade II Patnaik tumors can be difficult to predict. In addition, if metastasis has occurred in normal-sized lymph nodes, palpation alone is an insensitive measure.^18,19 In this dog, location of the MCT is also important; metastasis may spread cells from the pinna to the mandibular lymph node, but there may also be predisposition to spreading to the prescapular or superficial cervical lymph node.¹⁵ This is important, as most dogs with distant metastasis also have concurrent lymph node involvement.²⁰ Lymph node metastasis may then prompt further staging with aspirates of the liver and spleen.²¹ 

Buffy coat smears have been found to have low sensitivity, with higher mastocytemia noted in dogs with non-MCT–related disorders; for this reason, buffy coat evaluation is not part of routine MCT staging.²²

Staging diagnostics should be completed for all grade II Patnaik MCTs. Appropriate staging should include FNA of mandibular and prescapular lymph nodes and abdominal ultrasonography, and in some cases FNA of the liver and spleen.^15-17 Tumor grade has been prognostic for end points (eg, survival, disease-free interval); and high-grade tumors, regardless of whether graded on the Patnaik or Kiupel scheme, have an increased rate of metastasis. Grade II Patnaik tumors can be difficult to predict. In addition, if metastasis has occurred in normal-sized lymph nodes, palpation alone is an insensitive measure.^18,19 In this dog, location of the MCT is also important; metastasis may spread cells from the pinna to the mandibular lymph node, but there may also be predisposition to spreading to the prescapular or superficial cervical lymph node.¹⁵ This is important, as most dogs with distant metastasis also have concurrent lymph node involvement.²⁰ Lymph node metastasis may then prompt further staging with aspirates of the liver and spleen.²¹ 

Buffy coat smears have been found to have low sensitivity, with higher mastocytemia noted in dogs with non-MCT–related disorders; for this reason, buffy coat evaluation is not part of routine MCT staging.²²

Staging diagnostics should be completed for all grade II Patnaik MCTs. Appropriate staging should include FNA of mandibular and prescapular lymph nodes and abdominal ultrasonography, and in some cases FNA of the liver and spleen.^15-17 Tumor grade has been prognostic for end points (eg, survival, disease-free interval); and high-grade tumors, regardless of whether graded on the Patnaik or Kiupel scheme, have an increased rate of metastasis. Grade II Patnaik tumors can be difficult to predict. In addition, if metastasis has occurred in normal-sized lymph nodes, palpation alone is an insensitive measure.^18,19 In this dog, location of the MCT is also important; metastasis may spread cells from the pinna to the mandibular lymph node, but there may also be predisposition to spreading to the prescapular or superficial cervical lymph node.¹⁵ This is important, as most dogs with distant metastasis also have concurrent lymph node involvement.²⁰ Lymph node metastasis may then prompt further staging with aspirates of the liver and spleen.²¹ 

Buffy coat smears have been found to have low sensitivity, with higher mastocytemia noted in dogs with non-MCT–related disorders; for this reason, buffy coat evaluation is not part of routine MCT staging.²²

Staging diagnostics should be completed for all grade II Patnaik MCTs. Appropriate staging should include FNA of mandibular and prescapular lymph nodes and abdominal ultrasonography, and in some cases FNA of the liver and spleen.^15-17 Tumor grade has been prognostic for end points (eg, survival, disease-free interval); and high-grade tumors, regardless of whether graded on the Patnaik or Kiupel scheme, have an increased rate of metastasis. Grade II Patnaik tumors can be difficult to predict. In addition, if metastasis has occurred in normal-sized lymph nodes, palpation alone is an insensitive measure.^18,19 In this dog, location of the MCT is also important; metastasis may spread cells from the pinna to the mandibular lymph node, but there may also be predisposition to spreading to the prescapular or superficial cervical lymph node.¹⁵ This is important, as most dogs with distant metastasis also have concurrent lymph node involvement.²⁰ Lymph node metastasis may then prompt further staging with aspirates of the liver and spleen.²¹ 

Buffy coat smears have been found to have low sensitivity, with higher mastocytemia noted in dogs with non-MCT–related disorders; for this reason, buffy coat evaluation is not part of routine MCT staging.²²

Staging diagnostics should be completed for all grade II Patnaik MCTs. Appropriate staging should include FNA of mandibular and prescapular lymph nodes and abdominal ultrasonography, and in some cases FNA of the liver and spleen.^15-17 Tumor grade has been prognostic for end points (eg, survival, disease-free interval); and high-grade tumors, regardless of whether graded on the Patnaik or Kiupel scheme, have an increased rate of metastasis. Grade II Patnaik tumors can be difficult to predict. In addition, if metastasis has occurred in normal-sized lymph nodes, palpation alone is an insensitive measure.^18,19 In this dog, location of the MCT is also important; metastasis may spread cells from the pinna to the mandibular lymph node, but there may also be predisposition to spreading to the prescapular or superficial cervical lymph node.¹⁵ This is important, as most dogs with distant metastasis also have concurrent lymph node involvement.²⁰ Lymph node metastasis may then prompt further staging with aspirates of the liver and spleen.²¹ 

Buffy coat smears have been found to have low sensitivity, with higher mastocytemia noted in dogs with non-MCT–related disorders; for this reason, buffy coat evaluation is not part of routine MCT staging.²²

Complete excision of all gross disease would be recommended, including resection of the primary tumor and metastatic lymph node. Regional metastasis does not necessarily portend a poor prognosis if it can be addressed surgically. One study did not find a difference in survival of dogs with or without lymph node metastasis, meaning the metastatic lymph node did not negatively impact survival when treated appropriately.¹⁹ Adjuvant chemotherapy is generally recommended in patients with high-risk MCTs, including those that are metastatic and/or high grade.²³ Long-term survival has been described in dogs treated with adequate local control and chemotherapy in a population of dogs with grade II, stage II tumors (ie those with lymph node metastasis) where the median survival time was not reached at a follow-up time of 65.9 months.²³ 

Complete excision of all gross disease would be recommended, including resection of the primary tumor and metastatic lymph node. Regional metastasis does not necessarily portend a poor prognosis if it can be addressed surgically. One study did not find a difference in survival of dogs with or without lymph node metastasis, meaning the metastatic lymph node did not negatively impact survival when treated appropriately.¹⁹ Adjuvant chemotherapy is generally recommended in patients with high-risk MCTs, including those that are metastatic and/or high grade.²³ Long-term survival has been described in dogs treated with adequate local control and chemotherapy in a population of dogs with grade II, stage II tumors (ie those with lymph node metastasis) where the median survival time was not reached at a follow-up time of 65.9 months.²³ 

Complete excision of all gross disease would be recommended, including resection of the primary tumor and metastatic lymph node. Regional metastasis does not necessarily portend a poor prognosis if it can be addressed surgically. One study did not find a difference in survival of dogs with or without lymph node metastasis, meaning the metastatic lymph node did not negatively impact survival when treated appropriately.¹⁹ Adjuvant chemotherapy is generally recommended in patients with high-risk MCTs, including those that are metastatic and/or high grade.²³ Long-term survival has been described in dogs treated with adequate local control and chemotherapy in a population of dogs with grade II, stage II tumors (ie those with lymph node metastasis) where the median survival time was not reached at a follow-up time of 65.9 months.²³ 

Complete excision of all gross disease would be recommended, including resection of the primary tumor and metastatic lymph node. Regional metastasis does not necessarily portend a poor prognosis if it can be addressed surgically. One study did not find a difference in survival of dogs with or without lymph node metastasis, meaning the metastatic lymph node did not negatively impact survival when treated appropriately.¹⁹ Adjuvant chemotherapy is generally recommended in patients with high-risk MCTs, including those that are metastatic and/or high grade.²³ Long-term survival has been described in dogs treated with adequate local control and chemotherapy in a population of dogs with grade II, stage II tumors (ie those with lymph node metastasis) where the median survival time was not reached at a follow-up time of 65.9 months.²³ 

Complete excision of all gross disease would be recommended, including resection of the primary tumor and metastatic lymph node. Regional metastasis does not necessarily portend a poor prognosis if it can be addressed surgically. One study did not find a difference in survival of dogs with or without lymph node metastasis, meaning the metastatic lymph node did not negatively impact survival when treated appropriately.¹⁹ Adjuvant chemotherapy is generally recommended in patients with high-risk MCTs, including those that are metastatic and/or high grade.²³ Long-term survival has been described in dogs treated with adequate local control and chemotherapy in a population of dogs with grade II, stage II tumors (ie those with lymph node metastasis) where the median survival time was not reached at a follow-up time of 65.9 months.²³ 

The boxer breed has a well-established overrepresentation for developing MCTs. Although findings in one study suggested that boxers are more likely to have lower-grade tumors, MCTs of a higher grade cannot be completely ruled out.²⁴

Once a dog of any breed has a MCT, there is a 20% to 40% chance of developing another tumor in its lifetime. Therefore, counseling owners on the importance of monitoring for new masses is essential.²⁵ Because new MCTs are often considered to be de novo (ie, new process) and not metastasis of previous tumors, development of a new MCT does not necessarily denote a poor prognosis. Rather, research⁵ has suggested a favorable prognosis in dogs with multiple MCTs. Each new tumor should, therefore, be addressed individually, and histopathologic grade should be used to guide treatment decisions as well as discussions (with owners) regarding prognosis.⁵

The boxer breed has a well-established overrepresentation for developing MCTs. Although findings in one study suggested that boxers are more likely to have lower-grade tumors, MCTs of a higher grade cannot be completely ruled out.²⁴

Once a dog of any breed has a MCT, there is a 20% to 40% chance of developing another tumor in its lifetime. Therefore, counseling owners on the importance of monitoring for new masses is essential.²⁵ Because new MCTs are often considered to be de novo (ie, new process) and not metastasis of previous tumors, development of a new MCT does not necessarily denote a poor prognosis. Rather, research⁵ has suggested a favorable prognosis in dogs with multiple MCTs. Each new tumor should, therefore, be addressed individually, and histopathologic grade should be used to guide treatment decisions as well as discussions (with owners) regarding prognosis.⁵

The boxer breed has a well-established overrepresentation for developing MCTs. Although findings in one study suggested that boxers are more likely to have lower-grade tumors, MCTs of a higher grade cannot be completely ruled out.²⁴

Once a dog of any breed has a MCT, there is a 20% to 40% chance of developing another tumor in its lifetime. Therefore, counseling owners on the importance of monitoring for new masses is essential.²⁵ Because new MCTs are often considered to be de novo (ie, new process) and not metastasis of previous tumors, development of a new MCT does not necessarily denote a poor prognosis. Rather, research⁵ has suggested a favorable prognosis in dogs with multiple MCTs. Each new tumor should, therefore, be addressed individually, and histopathologic grade should be used to guide treatment decisions as well as discussions (with owners) regarding prognosis.⁵

The boxer breed has a well-established overrepresentation for developing MCTs. Although findings in one study suggested that boxers are more likely to have lower-grade tumors, MCTs of a higher grade cannot be completely ruled out.²⁴

Once a dog of any breed has a MCT, there is a 20% to 40% chance of developing another tumor in its lifetime. Therefore, counseling owners on the importance of monitoring for new masses is essential.²⁵ Because new MCTs are often considered to be de novo (ie, new process) and not metastasis of previous tumors, development of a new MCT does not necessarily denote a poor prognosis. Rather, research⁵ has suggested a favorable prognosis in dogs with multiple MCTs. Each new tumor should, therefore, be addressed individually, and histopathologic grade should be used to guide treatment decisions as well as discussions (with owners) regarding prognosis.⁵

The boxer breed has a well-established overrepresentation for developing MCTs. Although findings in one study suggested that boxers are more likely to have lower-grade tumors, MCTs of a higher grade cannot be completely ruled out.²⁴

Once a dog of any breed has a MCT, there is a 20% to 40% chance of developing another tumor in its lifetime. Therefore, counseling owners on the importance of monitoring for new masses is essential.²⁵ Because new MCTs are often considered to be de novo (ie, new process) and not metastasis of previous tumors, development of a new MCT does not necessarily denote a poor prognosis. Rather, research⁵ has suggested a favorable prognosis in dogs with multiple MCTs. Each new tumor should, therefore, be addressed individually, and histopathologic grade should be used to guide treatment decisions as well as discussions (with owners) regarding prognosis.⁵