Unknown mass in 12-year-old corgi mix - any thoughts?

Hi everyone,

Posting here in case any vets can help shed some light on our poor corgi mix's unknown mass.

He started limping around 5/13 and we brought him to an urgent care quickly after. He was found to have a mass in his RF limb that was suspicious of a malignant tumor. FNA was performed which was inconclusive. We then established with an oncologist shortly after who recommended a CT scan with a needle biopsy. Again the biopsy did not reveal a diagnosis. We've since met with the surgeon yesterday who said that the mass has grown in size in the 1.5 weeks since his CT, and she recommends an amputation but can't comment on our dog's prognosis given the lack of diagnosis.

I feel so lost and while we scheduled our dog for amputation this Wednesday, I can't help but question if this is the right decision for him. I just want to prioritize his quality of life. The surgeon did confirm that he would be a good surgical candidate, but I don't know if we're making the right call.

I've attached some of the results below. Any input you might provide would be greatly appreciated.

5/16 FNA
INTERPRETATION:

Chronic inflammation with few mesenchymal cells and evidence of acute and chronic

hemorrhage. See comments.

COMMENTS:

With inflammation, the mesenchymal cells described could be representative of a reactive

population of fibroblasts occurring secondary to inflammation or granuloma formation; however,

a hemorrhagic mesenchymal neoplasm (i.e. hemangiosarcoma or other vascular soft tissue

sarcoma) cannot be excluded definitively. The low number of mesenchymal cells present

precludes further interpretation. Hemorrhage can be seen with seromatous lesions, tissue

trauma, chronic inflammation, or with vascular tissue. With the poorly exfoliative nature of this

mass, tissue biopsy with histopathology is recommended for further characterization of this mass,

particularly if this mass is persistent or progressive.

5/28 CT scan and biopsy

CT scan, thorax and right thoracic limb- There is a large, poorly marginated, soft

tissue attenuating mass (60HU) originating from the medial soft tissues of the

right forelimb, which exhibits strong, wispy peripheral enhancement. The mass

extends proximally and caudally from the mid-diaphysis of the radius to the mid-

diaphysis of the humerus (Figure 1, pink arrowheads). There is marginal

effacement of the mass and the adjacent musculature, which appears enlarged.

The adjacent bone appears normal. There is thickening and streaky

hyperattenuation of the subcutis distal to the mass and the ventral subcutis of

the cranial abdominal trunk. The cervical and axillary (Figure 1, yellow

arrowheads) lymph nodes appear within normal limits. There are occasional

mineralised foci within the pulmonary parenchyma, compatible with incidental

heterotopic bone. The pulmonary parenchyma is evaluated and no additional

abnormalities are detected. The heart and pulmonary vasculature appear within

normal limits. The sternal, cranial mediastinal and tracheobronchial lymph

nodes are normal. The trachea and oesophagus are evaluated and appear within

normal limits. The mediastinum and mediastinal structures appear normal.

There are osteophytes associated with the elbows. There is mineralisation of

several intervertebral discs. There is thoracic spondylosis. There is a focal area

of strong enhancement within the left hepatic parenchyma. There is mineralised

material within the gallbladder. There is a small (6mm maximum thickness),

hypoattenuating nodule within the spleen, which weakly enhances. There is a

focal area of strong enhancement within the spleen. The cranial pole of the right

adrenal is rounded and exhibits strong, heterogeneous enhancement. All other

bone and soft tissue structures of the thorax are evaluated and no additional

abnormalities are detected.

◦ Conclusions:

Non-specific soft tissue mass, right forelimb (see comment).

Probable peripheral oedema.

Non-specific splenic nodule, likely benign.

Non-specific hepatopathy, likely benign.

Cholelithiasis.

Possible small right adrenal nodule, likely benign.

Bilateral elbow osteoarthritis.

◦ Additional Comments: There is a non-specific soft tissue mass originating

from the soft tissues of the right forelimb, which is likely contributing to

the peripheral oedema. The mass is large and there is associated marginal

effacement of the adjacent musculature. Local infiltration is suspected.

Differentials include neoplasia such as sarcoma or mast cell tumour.

Benign disease such as a granuloma cannot be completely ruled out.

Sampling is required to achieve a definitive diagnosis. Repeat sampling of

the right forelimb mass lesion is recommended. No evidence of a local

lymphadenopathy is detected at the time of study. No evidence of

pulmonary metastasis is detected at the time of study. There is a small

non-specific splenic nodule. A benign regenerative hyperplasia or

extramedullary haematopoiesis is suspected. Other differentials cannot be

completely ruled out. Ultrasound-guided fine needle aspiration may be

helpful to further evaluate the splenic nodule, if clinically indicated.

• Histopathology, right thoracic limb mass (SVP)- Dissecting fibrosis with mild to

moderate pleocellular cellulitis. These biopsies are composed muscle and

surrounding connective tissue that is dissected by bands of mucinous spindle

cells arranged in a densely packed organized streams. They are occasionally

admixed with hemorrhage as well and there as infiltration by small to

occasionally moderate numbers of lymphocytes, plasma cells and few

neutrophils. Portions of the muscle are also mildly fibrotic and atrophied. There

is no evidence of neoplasia.