RADIOGRAPHIC CHANGES ASSOCIATED WITH DIGITAL, METACARPAL AND METATARSAL TUMORS, AND PODODERMATITIS IN THE DOG

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1 RADOGRAPHC CHANGES ASSOCATED WTH DGTAL, METACARPAL AND METATARSAL TUMORS, AND PODODERMATTS N THE DOG ANDRA K. VOGES, DVM, LSA NEUWRTH, DVM, MS, JAMES P. THOMPSON, DVM, PHD, NORMAN ACKERMAN, DVM Fifty-two of digital, metacarpal or metatarsal canine tumors and 48 pododermatitis lesions were reviewed retrospectively. The tumors were divided into 4 malignant neoplasms, 6 benign neoplasms and 4 non-neoplastic tumor-like growths. The distribution and radiographic changes of the lesions associated with the tumors and inflammation were compared. Pododermatitis and benign processes could not be radiographically differentiated from malignant neoplasms of the foot; however, lesions exhibiting osteolysis were more likely (p <.5) to be associated with malignant neoplasms. Veterinary Radiology & Ultrasound, Vol. 7, No. 5, 996, pp 7-5. Key words: canine, dog, manus, pes, digit, tumor, neoplasia, inflammation, pododermatitis, radiography. ntroduction AROUS NEOPLASMS AND non-neoplastic masses, including squamous cell carcinoma, melan~ma,~ epidermoid cyst,' n~astocytoma, plasinacytoma,6 hemangio- ~arcoma,~ pericytoma,' and calcinosis circumscripta9-' ' have been reported in canine digits. Several of these reports have included the radiographic findings. However, studies comparing the radiographic changes of tumors to those associated with inflammatory disease have not been reported. This retrospective study summarizes radiographic findings and anatomic distribution of digital, metacarpal and metatarsal neoplasms and compares these observations with those occurring secondary to pododermatitis. Materials and Methods The medical records of dogs with tumors or inflammation distal to the carpus or tarsus which had been examined at the University of Florida, Veterinary Medical Teaching Hospital between 979 and 994 were reviewed retrospectively. The records were examined for lesion location, histology, and radiographic changes. Histologic confirmation via biopsy or amputation was required for inclusion in this study. From the Department of Small Animal Clinical Sciences (AV, LN, JT), University of Florida, College of Veterinary Medicine, Box, Gainesville, FL 6CL-. Address correspondence and reprint requests to Dr. Voges. Published as University of Florida, College of Veterinary Medicine, Journal Series number 96. Received for publication January 9, 995; accepted September, 995. Patients with inflammation secondary to fractures and fracture fixation were excluded. The radiographs were individually evaluated and the changes were agreed upon by a radiologist (LN) and radiology resident (AV) for soft tissue and bony involvement. Multiple digit involvement was defined as skeletal changes involving more than digit, soft tissue swelling involving more than digit, or interdigital swelling even if the bony changes only involved one digit. Soft tissue swelling was defined as an increased thickness of the soft tissues distal to the carpus or tarsus. Periosteal new bone was defined as bony proliferation external to the normal cortical margins, excluding those changes associated with degenerative joint disease. Loss of normal cortical or medullary architecture with decreased radiographic opacity or coarse trabeculation secondary to overall bone loss was considered osteolysis. A tumor was defined as any uncontrolled and progressive growth of abnormal cells, which includes both benign and malignant neoplasms, as well as non-neoplastic masses. Pododermatitis, relative to this study, was defined as any inflammatory condition of the foot. nflammatory conditions of the foot included both septic and nonseptic processes. Conditions such as pyogranulomatous inflammation, cellulitis, deep pyoderma, dermatitis, granulation tissue and acral lick dermatitis were all included in this study. The radiographic findings were subjectively compared to the histopathologic diagnosis to determine if there were any consistent findings that could be used to support a radiographic diagnosis of tumor versus pododermatitis. Chisquare analyses were used to compare the radiographic findings of soft tissue swelling, periosteal new bone, bone lysis, combined lysis and periosteal reaction and soft tissue mineralization for significant (p <.5) correlations to a his- 7

2 8 VOGES ET AL 996 tologic diagnosis of malignant neoplasms or pododermatitis. Bone lysis secondary to disuse osteopenia was excluded in statistical analyses. Malignant Neoplasms Results Forty-two malignant neoplasms affecting the manus or pes of 4 dogs were identified (Table ). A single pes in dog was affected with two malignant neoplasms, an osteosarcoma and a cutaneous hemangiosarcoma. Another dog was similarly afflicted with squamous cell carcinoma and a non-neoplastic tumor-like growth, an epidermal inclusion cyst, also occurring within a single manus. The 4 malignant neoplasms were comprised of 5 histologic types (Table ). Squamous cell carcinoma was the most frequently encountered neoplasm and affected 5 dogs. Lesions were distributed between the manus and pes in 8 and 7 dogs, respectively. Twelve of the 5 squamous cell carcinomas affected only the digits, while tumors affected the digits and adjacent metacarpal or metatarsal regions, and tumor affected only the metacarpus. This dog had previously had a digital amputation. n the majority of the dogs, the tumor involved only a single digit, however, 4 dogs had multiple digit involvement. Soft tissue swelling was radiographically evident in all 5 dogs and 4 dogs also had radiographic evidence of bone involvement; 4 dogs exhibited osteolysis and 9 concurrent periosteal bone proliferation (Fig., Table ). None of the dogs had periosteal bone proliferation in the absence of bone destruction (Fig. ). n two dogs with periosteal bone proliferation and osteolysis, the bone lysis was characterized as a diffuse osteopenia and was considered consistent with osteolysis secondary to disuse. Soft tissue mineralization was evident in one dog with squamous cell carcinoma. Mast cell tumors were identified in 4 dogs. The tumors were present in the manus in dogs and in the pes in dog. One tumor involved multiple digits, one tumor a single digit and the metacarpus, and the remaining tumor affected the metacarpus only. Soft tissue swelling was evident in of the 4 dogs. Bone involvement and soft tissue mineralization were not observed. n one dog with a mast cell tumor, there were no radiographic abnormalities. Four dogs were afflicted with melanoma. Three tumors were in the manus and one in the pes. Each of the melanomas affected only a single digit and none occurred within the metacarpus or metatarsus. All of the dogs had radiographic evidence of soft tissue swelling and bone involve- TABLE. Radiographic Changes Associated with Tumors and nflammatory Diseases Affecting the Manus/Pes No. Patients with Radiographic Changes Disease Disease No. Soft Tissue Periosteal Bone Periosteal New Bone Soft Tissuc Process Classification Patients Swelling New Bone Lysis* and Bone Lysis* Mineralization Normal Tumor nflammation Malignant neoplasm Squamous cell carcinoma Mast cell tumor Melanoma Osteosarcoma Hemangiosarcoma Hemangioperic ytoma Plasmacytoma Synovial cell sarcoma Undifferentiated sarcoma Adenocarcinoma Neurofibrosarcoma Fibrosarcoma Sebaceous gland adenocarcinoma Adenosquamous carcinoma Carcinoma Benign neoplasm Histiocytoma Lipoma Papilloma Osteochondroma Non-neoplastic tumor-like growth Epidermal inclusion cyst Calcinosis circumscripta Pododermatitist *Bone lysis denotes tumor-induced bone destruction. Diffuse osteolysis assessed as a secondary phenomenon related directly to disuse osteopenia was not considered evidence of tumor-induced bone lysis. TPododermatitis included all categories of inflammatory diseases which were not associated with a malignant or benign neoplasm or a non-neoplastic tumor-like growth

3 VOL. 7, No. 5 CANNE FOOT 9 FG.. Squamous cell carcinoma of the distal phalanx of the fifth digit. Bone destruction of the distal phalanx and distal aspect of the middle phalanx and soft tissue swelling of the fifth digit are present. Note the relative absence of periosteal bone proliferation and the similar appearance to Figure (melanoma) and Figure 6 (pododermatitis). ment; one dog had periosteal bone proliferation only, dogs had osteolysis only, and the remaining dog had both periosteal bone proliferation and osteolysis (Fig. ). Soft tissue mineralization was not associated with the lesions. Osteosarcomas affected 4 dogs and there was an equal anatomic distribution between the manus and pes. Three tumors occurred within the digits while the remaining tumor involved a metacarpal bone. One dog had multiple digit involvement; this dog also had a cutaneous hemangiosarcoma affecting the same pes. Three of the dogs had soft tissue swelling, while all 4 dogs had radiographic evidence of bone involvement. One dog had periosteal bone proliferation only, dogs had osteolysis only, and the remaining dog had both periosteal bone proliferation and osteolysis. rregular osteolysis was present at a distal amputation site in dogs. This osteolysis was considered consistent with tumor regrowth in the adjacent phalanx or metacarpal bone. Soft tissue mineralization was not associated with any of the lesions. Hemangiosarcomas affected dogs. The manus was affected in dog and the pes was affected in the remaining dogs. Two tumors involved multiple digits, while tumor involved multiple metatarsal bones. All dogs had soft tissue swelling and bone involvement. One dog had both bone formation and destruction, dog had periosteal bone formation only, and the remaining dog had osteolysis only; this dog also had a concurrent osteosarcoma affecting the same pes. Hemangiopericytomas were observed in dogs. One tumor occurred in the manus and tumors in the pes. The tumor was associated with radiographic changes in only a single digit in dogs, while multiple digits were affected in the remaining dog. The metacarpus and metatarsus were unaffected. All hemangiopericytomas were characterized by soft tissue swelling, but there was no evidence of bone involvement. Soft tissue mineralization was not associated with the lesions. The remaining 9 tumor types were present in only dog

4 VOGES ET AL 996 coma was not characterized by any radiographic abnormalities. Benign Neoplasms Six benign tumors, consisting of 4 histologic types, were diagnosed in 6 dogs (Table ). Histiocytomas were diagnosed in dogs and each affected the manus. One of these tumors involved a single digit, while the other affected multiple digits. Neither tumor affected the metacarpus. Both tumors were associated with soft tissue swelling, but neither induced evidence of bone involvement nor soft tissue mineralization. Lipomas were also identified in dogs. One was a simple lipoma which affected multiple digits of the manus. The other was an infiltrative lipoma which affected the metacarpus (Fig. 4). Both dogs had radiographic evidence of soft tissue swelling. The infiltrative lipoma was associated with periosteal bone proliferation and osteolysis (Fig. 4). Soft tissue mineralization was not associated with either lipoma. A papilloma and an osteochondroma comprised the remaining tumors and affected dog each (Table ). Both tumors affected the digits of the pes and neither involved the metatarsus. The papilloma affected multiple digits; however, the osteochondroma was confined to a single digit only. The papilloma was associated with only soft tissue swelling, while the osteochondroma had periosteal bone proliferation and osteolysis. FG.. Squamous cell carcinoma resulting in diffuse soft tissue swelling. The soft tissue swelling is most pronounced in the interdigital space between the third and fourth digits, causing digit separation. Periosteal bone proliferation (arrowheads) is present on the axial surfaces of the proximal phalanges of the third and fourth digits. Diffuse osteopenia is present, as evidenced by coarse trabeculation. This soft tissue neoplasm has an appearance more typical of inflammatory conditionb (See Figure 5). each (Table ). Four tumors were located in the manus and 5 were located in the pes. The plasmacytoma, undifferentiated sarcoma, neurofibrosarcoma, fibrosarcoma, and carcinoma affected the digits only, while the synovial cell sarcoma, adenocarcinoma, and adenosquamous carcinoma affected the metatarsus and digits and the sebaceous gland adenocarcinoma affected only the metatarsus. Multiple digits were affected by the plasmacytoma, synovial cell sarcoma, adenocarcinoma, adenosquamous carcinoma, and carcinoma. Soft tissue swelling was associated with each tumor except the neurofibrosarcoma. Periosteal bone proliferation was associated with the synovial cell sarcoma, undifferentiated sarcoma, adenocarcinoma, and adenosquamous carcinoma. Osteolysis was also present in the synovial cell sarcoma and undifferentiated sarcoma, along with the carcinoma. Soft tissue mineralization was radiographically evident only in the fibrosarcoma. The neurofibrosar- Non-neoplastic Tumor-like Growths Non-neoplastic tumor-like growths included epidermal inclusion cysts and calcinosis circumscripta which occurred in dogs and dog, respectively. The epidermal inclusion cysts were present in the manus in dogs and in the pes in dog. The tumor was associated with radiographic changes in only a single digit in dogs, while multiple digits were affected in the remaining dog. The metacarpus and metatarsus were unaffected. All tumors were associated with soft tissue swelling. Only dog had radiographic evidence of bone involvement which consisted of periosteal bone proliferation and osteolysis; it should be noted, however, that this patient also had a concurrent squamous cell carcinoma located in the same manus. Based upon histopathologic analysis, it was believed the squamous cell carcinoma was responsible for the periosteal bone proliferation and osteolysis. Soft tissue mineralization was not associated with the lesions. The calcinosis circumscripta lesion occurred in the manus and affected multiple digits and the metacarpus. Soft tissue swelling and bone involvement were not associated with the lesion; however, soft tissue mineralization was observed. Pododermatitis Radiographic findings associated with inflammatory conditions affecting 48 separate manuslpedes in 4 dogs were

5 VOL. 7, No. 5 CANNE FOOT FG.. Melanoma resulting in bone destruction of the distal phalanx of the fifth digit. There is soft tissuc swelling of this digit with mild periosteal bone proliferation. Note the similar appearance of the squamous cell carcinoma shown in Figure. evaluated. The manus was affected slightly more often than the pes: 6 and, respectively. The digits only were involved in manus/pedes, while the digits and metacarpus or metatarsus were affected in 9 and the metacarpus or metatarsus only were involved in the remaining 6. Multiple digits were affected in 8 manuslpedes and 4 dogs had multiple manusipedes affected. Radiographic evidence of soft tissue swelling was present in all 48 manuslpedes, most of which had irregular soft tissue margins indicative of ulceration or soft tissue proliferation. Twenty-five of 48 manudpedes had evidence of bone involvement. The skeletal changes included manudpedes with periosteal bone proliferation only (Fig. 5), 5 manus/pedes with osteolysis only, and 9 manuslpedes with concurrent periosteal bone proliferation and osteolysis (Fig. 6, Table ). Diffuse osteopenia consistent with disuse was present in manudpes with osteolysis only and in dog with both periosteal bone proliferation and osteolysis. Soft tissue mineralization was present in 7 manudpedes (Fig. 7). Chi-square were performed t' identify tion between specific radiographic abnormalities and either FG. 4. nfiltrative lipoma seen as a large mass with varying opacity on the palmar aspect of the metacarpus. rregular periosteal new bone formation with palmar cortical osteolysis is present on the fifth metacarpal and proximal sesamoid bones.

6 VOGES ET AL 996 FG. 5. Typical pododermatitis. There is soft tissue swclling of the fourth digit with periosteal bonc proliferation (arrows) present on the middle phalanx. malignant neoplasms of the feet or underlying pododermatitis; insufficient numbers of benign neoplasms and nonneoplastic tumor-like growths were present for accurate statistical assessment. There was no significant association between lesion location, soft tissue swelling, periosteal bone proliferation, and soft tissue mineralization between malignant neoplasms and pododermatitis. A significant association was, however, identified between osteolysis and malignant neoplasms; the presence of osteolysis was more likely to be associated with a malignant neoplasm than with an underlying pododermatitis. t should be noted, however, that although statistically significant (p =.4), the presence of osteolysis was not conclusive evidence of a malignant disease process, as osteolysis, radiographically indistinguishable in appearance, was also present in dogs with benign neoplasms as well as in dogs with pododermatitis lesions. Discussion Tumors and inflammatory processes occurred in the canine manudpes with a fairly even occurrence. Malignant neoplasms occurred more frequently than benign neoplasms (Table ). Squamous cell carcinoma was the most frequently encountered tumor in this retrospective study, as previously n both earlier reports, melanomas were the next most common; however, inast cell tumors and melanomas were equally prevalent in this study. All tumors in this retrospective study have previously been reported to occur in the canine manus/pes. The signalment of patients in this retrospective study was similar to that in previously published reports. Both tumors and inflammation were fairly evenly distributed between the manus and pes. t has been reported that mast cell tumors to have a predilection for the hindquarhowever, in this study, of the 4 tumors occurred in the manus. The classic osteosarcoma which occurs in long bones was reported to occur in the forelimbs of large breeds with a.6: ratio of front:hind limbs. 4 There was an equal distribution of osteosarcomas between the manus and pes in this report. Hemangiopericytomas were reported to commonly occur in the forelimbs or thigh;4 however, in this

7 VOL. 7, No. 5 CANNE FOOT FG. 6. Pododermatitis resulting in diffuse irregular soft tissue swelling. Osteolysis (whitc arrows) of the distal aspect of the distal phalanx of thc third digit is present. Mild pcriosteal new bone formation (black arrowheads) is present on the middle phalanx of the third digit. Note the similarity of these changes with those radiographic changes shown in Figures (squamous cell carcinoma) and (melanoma). study, lesions were in the pes with only in the manus. As reported previously, 4 histiocytomas occurred more frequently in the manus in this study. As expected, the distribution of lesions affecting the metacarpus or metatarsus, digits and either the metacarpus or metatarsus and digits had a relatively equal occurrence in both tumors and inflammation. Both tumors and pododermatitis more commonly affected the digit rather than the metacarpal or metatarsal regions. Multiple toe involvement was slightly more common in patients with pododermatitis versus tumors, and four dogs with pododermatitis had multiple feet affected. Multiple tumors were present in dogs: an osteosarcoma and hemangiosarcoma in the same pes of dog, and a squamous cell carcinoma and epidermal inclusion cyst in the same manus of the other dog. Pododermatitis occurred in dog in which a mast cell tumor had previously been removed. Soft tissue swelling was a predominant radiographic finding for both digital tumors and inflammation. The swelling tended to be more irregular with inflammatory conditions, being consistent with ulceration or soft tissue proliferation (Figs. 5 & 6). The mast cell tumors in this study were all characterized by soft tissue swelling without associated bony changes. t has been reported that hemangiopericytomas have soft tissue swelling with no bone involvement;* the hemangiopericytomas in this report had similar findings. Other tumors which had soft tissue swelling with no bone involvement included the plasmacytoma, fibrosarcoma, sebaceous gland adenocarcinoma, histiocytomas, papilloma and calcinosis circumscripta. Both pododermatitis and digital tumors caused skeletal changes, with a frequency of 5.% (.948) and 6.5% (/5), respectively (Table ). These changes could be due to local invasion by the tumor or inflammatory changes from local irritation. Periosteal new bone forms when pus, edema, hemorrhage or tumor cells elevate the periosteum from the cortex, which provides a framework for new bone formation. 5 Bony destruction occurs as a result of pressure

8 4 VOGES ET AL 996 FG. 7. Extensive soft tissue mineralization of the middle phalanx of the third digit secondary to chronic inflammation. This mineralization is most prominent on the palmar aspect of the digit. Mild diffuse osteopenia is present evidenced as by thc coarsc trahcculation in the metacarpus. necrosis or direct invasion. Both tumors and inflammation caused proliferative and destructive changes. Although not statistically significant, there appeared to be a tendency for inflammatory changes to be proliferative and tumors to be destructive. There were 5 dogs with pododermatitis in which bony destruction was present without proliferation, and the osteolysis was due to disuse osteopenia in of these (Figs. 5, 6 and 7). Periosteal new bone in the absence of osteolysis was present in only the following tumors: hemangiosarcomas, an osteosarcoma, a mast cell tumor, the adenocarcinoma, the adenosquamous carcinoma, and the synovial cell sarcoma. Squamous cell carcinoma had appearances: a primarily destructive lesion involving the distal phalanx (Fig. ) or diffuse soft tissue swelling with periosteal proliferation (Fig. ). The primarily destructive lesions were similar to those previously reported. Squamous cell carcinomas have been reported to cause lysis and periosteal new bone produ~tion;*~~ lysis of the distal phalanx has been described with squamous cell carcinomas.' Nine of 5 patients with squamous cell carcinoma in this study had both osteolysis and periosteal new bone formation; five had only bone destruction. As has been rep~rted,~,'~ the melanomas in this study also commonly invaded bone causing destruction, particularly of the distal phalanx. This had a similar radiographic appearance to the more common appearance of squamous cell carcinoma (Figs. and ). Synovial cell carcinoma has been reported to cause both bone destruction and proliferation" as was observed in this study. nfiltrative lipomas have been reported to cause bone lysis of the spine and pelvis7 and distal phalanx;" however, the infiltrative lipoma in this study caused both bone proliferation and lysis. Since pododermatitis (acral lick dermatitis, bacterial or fungal dermatitis, foreign body granulomas, etc) and digital neoplasms are the primary differential diagnoses for masses involving the manus or pes, it would be beneficial to differentiate malignant neoplasms from benign processes radiographically. Based on this retrospective study, this is not possible because of the wide variation in radiographic changes. However, malignant neoplasms should be suspected in those patients exhibiting osteolysis, as supported by statistical analysis.

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