In specialized skin areas, the disease profile is significantly influenced by regional variation in the nature/density of surface hair, distribution pattern of different types of glands, and skin thickness¹. The skin cover with fine hair on the scrotum is thin and highly pigmented. Sebaceous and apocrine glands are located in the dermis². The dartos muscle comprises smooth muscle with mixed collagen and elastic fibres³. Progressive vascular wall deformity in aging dogs^4,5,6 often leads to bleeding lesions with occasional exsanguinations⁷. In dogs, mast cell tumors (MCTs) represent the common scrotal neoplasms^8,9,10 and cutaneous MCTs constitute 7–21% of all body surface tumors, exhibiting biodegradation of varying nature and magnitude^11,12,13. Clinical manifestation of MCTs ranges from a solitary benign growth to terminal metastatic disease. Grading systems are designed to correlate with high fidelity the apparent histoarchitectural deformities with the severity of metaplastic transformation. The early highly cited grading system¹⁴ defines Grade 1 MCTs as the most differentiated in sharp contrast to Grade 3, the least differentiated growths. Grade 2 (40% frequency) refers to the intermediate degree of differentiation. This communication reports on a cutaneous mast cell tumor on the dog’s scrotum: high grade (Kiupel2-tier scale)¹⁵, or grade 3 (Patnaik 1–3 scale)¹⁴.

Bud Torosian, a 12-year-old neutered male English Pointer, weighing 27.6 kg was presented with anoval (1.3 x 2.0 cm²) bleeding mass on the scrotum to Med-Vet emergency health care on March 9, 2021. All the physiological parameters were within normal limits with no peripheral lymphadenopathy. Close scrutiny of the chest radiographs (Fig.1a, 1b) showed a radiopaque patch(*), highly suggestive of some space occupying lesion, presumably metastatic. Corroborative ultrasound guided biopsy was advised, but the owner declined because of the cost.

Mass excision surgery: Medications: (MedVet emergency): Cefpodoxime 200 mg tablet: 1 PO with food OD and Yunnan Baiyao (Chinese herbal food supplement for haemostasis): 2 capsules PO, TID dispensed for 14 days, starting from March 9, 2021: the first dose given in the clinic to stop bleeding from the mass with home care advisory to prevent the pet’s atempts to lick or chew on the scrotal area, and keep a watch on vomiting, diarrhea, or loss of appetite. The owner opted cost-effective mass removal at the home clinic, Milford Veterinary Clinic.

The dog patient Bud Torosian, fasted overnight, was admitted in the OT in the early morning hours of March 15, 2021 following medical health check clearance on March 10, 2021 (Fig. 2). The patient was sedated with acepromazine @ 0.025-0.2 mg/kg [10mg/ml] 0.2 ml and butorphanol tartrate @ 0.2mg/ kg [10mg/ml] 0.5 ml, injected subcutaneously (S/C). After 30 minutes anaesthesia was induced with ketamine @ 2–10 mg/kg [50 mg/ml] and midazolam @ 0.1-0.3 mg/kg [5mg/ ml] 1.5 ml each, injected I/V. After intubation, the dog was transferred to isoflurane gas anesthesia (initial flow rate 2.5%, adjusted suitablywith the patient’s reflexes), hooked to the auto monitoring systems for EKG, blood pressure, O₂ levels and pulse rate. The scrotal surgical site was prepared by clipping, and cleaning with surgical scrub. An elliptical incision (Fig. 3) was made with safemargins on all sides. The entire mass was carefully dissected out with a pair ofMetzenbaum scissors. Haemostasis in the MCT bleeder wasensured, ligatingwith 3–0 absorbable suture. Thesubcutaneous layer was closed in the simple interrupted pattern andthe subcutis in simple continuous patternwith the same absorbable suture. Finally, the outermost skin layer was closed with 3–0 nonabsorbable suture. Onebolus (200 ml) isosmotic balanced electrolytes solutionwas injected S/C to preempt possible dehydration. Injectable Ampicillin, broad-spectrum Penicillin@ 30 mg/kg[200 mg/ml] 4.2 ml, and Carprofen@ 2.2 mg/kg [50mg/ml] 1.2 ml were administered S/C. Home care supportmedicines were dispensed: Tramadol 50 mg tablets, one BID@ 2 mg/kg for 3 days, Cefpodoxime@ 5–10 mg/kg,200 mg tablets, one OD for 10 successive days, and Carprofen tablets BID for 5 days. The owner was briefed on the projected cutaneous suture removal in the clinic on day10-14 post-surgery.

Excision mass histopathology examination was done as per the standard procedures^16,17. In the instant case, an ulcerated 13 mmx20 mm oval mass (Fig. 4a) excised from the scrotumwas preserved in 10% neutral formaldehyde solution. In the Oncology Diagnostics Laboratory, the 4–5 μm thick sections, stained with H&E, were examined under the light microscope. Highlights of the microscopic profiles: the dermis and subcutis are infiltrated with poorly demarcated elevated mast cell neoplasm arranged in loose, or dense layers (Fig. 4b). The neoplastic cells exhibited distinct cell borders, moderate amount of basophilic granular cytoplasm, round to clearly visible indented nuclei, coarsely stippled chromatin, and 1–2 prominent nucleoli. Anisocytosis and anisokaryosis of moderate intensity are clearly seen. The intra-dermal collagen index (percentage of tumor mass occupied by the collagenous stroma) (Fig. 4c) is nearly 20%. Eosinophilic infiltration of the mass is evident. Notably, the epidermis appears ulcerated with blood-stained seropurulent exudate.

Histopathology profileof the scrotal cutaneous mass (Fig. 4d), suggestive of grade 3 mast cell tumorin the instant case, is corroborated by the evidence-based grading system¹⁴. Whereas histological grading is the most dependable prognostic indicator in pet practice, pathoclinical features specific to the individual patient also need to be considered in planning the optimized remedial strategy: curative surgery with or without adjuvant chemotherapy/radiation therapy. High morbidity/mortality rate is often associated with high grade MCTs exceeding 3cm in diameter concurrent with regional lymph node metastases¹⁵, and clinical signs like cutaneous ulcers, localized oedema, or gastrointestinal disorders: vomiting, melena, or diarrhoea^1,18. In the instant case, extended longevity of 6–12 months with improved quality of life is expected for the companion pet to the entire satisfaction of the well-informed owner.

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