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Lameness in an 11 year old Flat Coated Retriever

Welcome our radiographic case study for January 2021. This is an 11 year old FN Flat Coated Retriever with a one month history of left thoracic limb lameness. She had the nail removed from digit 5 on the left fore foot and has been on antibiotic therapy based on culture and sensitivity. However there was no improvement and the toe is now more swollen and she is almost non weight bearing now. On clinical exam there was severe swelling of the distal part of digit 5 on the LF, an enlarged pre scapular lymph node. No respiratory problems were noted. Bloods show 3x increase of ALP. Radiographs were taken to investigate:



Left fore foot


VD Thorax


Right lateral thorax


Left lateral thorax


Diagnostic Interpretation:


Thorax:

An ovoid soft tissue opaque nodular mass approximately 3.2 cm in height is noted in the dorsal thorax ventral to T6 and slightly caudal and dorsal to the carina with improved visualization of the margins on the right lateral views, in comparison the left lateral views (red arrowheads). This mass is not definitively identified on either ventrodorsal view although may be represented by the ill-defined increase soft tissue opacity indicated by the red arrowheads superimpose with the caudal aspect of the heart. There is a second, ill-defined, ovoid soft tissue opaque mass measuring approximately 2.7 cm length by at least 1 cm in height partially superimposed with the ventral aspect of T4 (yellow arrowheads) visible only on the right lateral views. A mild diffuse bronchial pulmonary pattern is present in the caudal dorsal lung lobes which is accentuated by mildly expiratory timing of acquisition of images. A right mediastinal shift is accentuated by obliquity and positioning on the ventro dorsal view. There are no further nodules or masses identified within the lungs. A small, ovoid, soft tissue opaque nodule is noted dorsal to the second sternabra in the cranial mediastinal reflection consistent with a sternal lymph node (green arrows). The heart and pulmonary vessels are normal. The trachea and oesophagus are normal. The pleural space is normal with no evidence effusion, nodules or masses The serosal detail in the cranial abdomen is adequate for the exposure factors in the study. The stomach contains performed heterogenous soft tissue opaque material likely representing a recently ingested meal. The remainder of the visible abdominal structures are normal. There is incidental narrowing of the intervertebral disc space with ventral spondylosis deformans at T6-7 and T13-L1. The remainder of the musculoskeletal structure surrounding the thorax are normal.


Left Carpus/Manus:

Moderate soft tissue thickening surrounds the left fifth digit from the level of the metacarpal phalangeal joint to the phalanx. Within the soft tissue swelling at the distal aspect of there is a smaller ovoid soft tissue opaque mass conflict with the distal phalanx. At the junction of this mass and the distal phalanx the bone margin is undulating and irregular. There is diffuse decreased opacity throughout the distal phalanx suggestive of mark diffuse lysis which extends to the proximal articular margin. The ungular process cannot be definitively identified. The distal interphalangeal joint is moderately widened and expanded. Columnar periosteal bone production extends along the medial and lateral margins of the middle phalanx and distal aspect of the proximal phalanx of this digit. There is a course trabecular bone pattern throughout the entire included distal limb, most severe in the distal radius, second and fifth digits characterized by small, well-defined, lucency is within the medullary cavity although the cortices remain normal in thickness with no evidence of lysis. There is subjective thickening of the soft tissue surrounding the third and fourth digit distal interphalangeal joint and distal phalanx which may be a positional artifact.


Conclusions:

 Aggressive bone lesion with associated small soft tissue opaque mass of the left fifth digit distal phalanx with associated regional soft tissue thickening and periosteal bone reaction extending proximally in the digit. The primary differential is neoplasia such as melanoma, osteosarcoma, squamous cell carcinoma or other soft tissue sarcoma. Given the mass effects associated with this region including expansion of the distal interphalangeal joint osteomyelitis secondary to severe pododermatitis is considered much less likely.

 At least one and probably two soft tissue pulmonary masses of the dorsal thorax. The primary differential is metastatic neoplasia secondary to the left fifth digit aggressive bone lesion. Atypical primary pulmonary neoplasia (carcinoma) with a local metastasis is considered much less likely.

 Sternal lymphadenopathy most likely represents metastatic neoplasia secondary to the left fifth digit aggressive bone lesion.

 Probable positional artifact versus soft tissue thickening surrounding the left third and fourth digits (pododermatitis or much less likely spread of the aggressive bone lesion of the fifth digit)

 Probable benign age-related fibrosis and imaging artifact/atelectasis, versus chronic bronchitis.

 Chronic intervertebral disc disease of the T6-7 and T 13-L1 disc spaces.


Additional comments:

The two masses identified within the thorax most likely represents metastatic neoplasia within the pulmonary parenchyma. The aggressive bone lesion of the left thoracic fifth digit most likely represents neoplasia. Biopsy of the left thoracic fifth digit, aggressive bone lesion/mass and or amputation and submission of the entire digit for histology is recommended to aid in reaching a definitive diagnosis in this patient. Additionally, tissue sampling of the reported large left superficial cervical lymph node may also be beneficial. Ultrasound-guided aspiration of the sternal lymph node can be considered.


Update:

The 5th digit of the left fore paw was amputated. Histology of the digit showed squamous cell carcinoma. Biopsy of the pre scapular lymph node showed reactive hyperplasia and no evidence of metastasis.