Skin masses in small animals

Question 1

5yo FN Labrador retriever
1cm erythematous nodule on dorsal aspect of radius
Little changed since first seen 2 weeks previously, though does appear to cause some irritation
What are your d/ds?

Answer 1

Penetrating wound causing infection/inflammation / cellulitis
Insect bite with inflammation
Mast cell tumour (MCT)
Histiocytoma

Question 2

Label this FNA cytology, what is your diagnosis and what would be your next steps?

Answer 2

Mast cell tumour

Metastatic potential so screen local lymph node +/- liver and spleen
Wide excision required
Histology would be required for grading

Question 3

3 yo FN Miniature Poodle, recently neutered at your surgery, when no abnormalities were detected
1.5cm diameter firm, painless interscapular nodule has subsequently developed.
What are your d/ds?

Answer 3

Injection reaction
Microchip reaction
Tumour eg spindle cell tumour, MCT
Cyst

Question 4

Label this FNA cytology, what is your diagnosis and what are your next steps?

Answer 4

Mixed inflammation within adipose tissue = panniculitis
No evidence of infection (but cannot preclude)
Classical appearance of an injection reaction
Usually resolves spontaneously

Question 5

Label this FNA cytology, what is your diagnosis and what are your next steps?

Answer 5

Mixed inflammation within adipose tissue = panniculitis
No evidence of infection (but cannot preclude)
Classical appearance of an injection reaction
Usually resolves spontaneously

Question 6

9yo MN Staffordshire Bull Terrier
3cm diameter well-defined soft mass on medial thigh. Enlarged slightly over past 6 months.
What are your d/ds?

Answer 6

Lipoma
Benign cyst
MCT
Low grade other neoplasm, e.g. spindle cell tumour , adnexal tumour

Question 7

Label this FNA cytology. What is your diagnosis?

Answer 7

Lipoma

Question 8

12yo MN DSH cat
Ill-defined swelling on left dorsal scapular region, noted first 3 days ago.
What are your d/ds?

Answer 8

Abscess / cellulitis
Sarcoma eg haemangiosarcoma, osteosarcoma, injection site sarcoma
Mast cell tumour

Question 9

Label this FNA cytology, give your diagnosis.

Answer 9

Septic inflammation:
- many neutrophils
- do not appear significantly degenerate but there are intracellular bacteria indicating infection
- consistent with an abscess/area of cellulitis e.g., due to cat bite

Question 10

11yo ME Labrador
Irregular, ill-defined firm nodule, 6cm diameter, over right caudal radius. Noted to have increased in size over past month
What are your d/ds?

Answer 10

Inflammatory mass
Neoplasm, esp spindle cell tumour

Question 11

Label this FNA cytology. give your diagnosis and next steps.

Answer 11

FNA consistent with spindle cell (mesenchymal) tumour
Biopsy required for histopathological diagnosis
Complete surgical excision if possible +/-radiotherapy if needed