A 14-month-old castrated male golden retriever was presented to a referral practice for evaluation of a cystic mass on its dorsal skull, medial and slightly rostral to the left ear.
The owner noticed acute onset of the golf-ball-sized mass three days before presentation, with no known associated trauma. Radiographic examination of the skull and cytologic examination of a fine-needle aspirate of the mass were performed two days earlier by the regular veterinarian. The results revealed a cystic subcutaneous mass over the frontal aspect of the skull and nonspecific suppurative inflammation. Six months before this presentation, the patient had a suspected cyst partially removed from the same location. The removed cystic segment was submitted for histologic examination, revealing a suspected incompletely removed dermoid sinus cyst.
Physical examination revealed ptosis of the left superior eyelid. Intact menace, pupillary light, and retractor bulbi responses were noted. Anisocoria, enophthalmus, and third eyelid protrusion were not seen. A large 5- to 6-cm raised soft movable mass over the left frontal and temporal skull was noted, which was painful on palpation.
Figure 1. A T1-weighted MRI contrast axial image of the frontotemporal subcutaneous cystic mass. Note the cavitary cyst lesion and surrounding extensive subcutaneous enhancement.
Complete blood cell count and serum chemistry profile results were unremarkable. Because of the previous suspicion of a dermoid sinus cyst, magnetic resonance imaging (MRI) was performed to further delineate the extent of the cyst and assess for potential sinus tracts. The MRI revealed a large cavitary subcutaneous mass along the left dorsal aspect of head, inciting a marked inflammatory reaction in the surrounding subcutaneous tissues. No evidence of communication with the central nervous system was noted (Figures 1 & 2).
Figure 2. A T1-weighted MRI contrast sagittal image of the frontotemporal subcutaneous cystic mass. Note the cavitary cyst lesion and surrounding extensive subcutaneous enhancement.
TREATMENT AND OUTCOME
The cystic mass was surgically resected. An elliptical incision was made over the cystic mass site, removing soft and necrotic skin. A large area of multicavitary cystic tissue was encountered; most of this tissue was resected en bloc down to underlying temporal fascia. Within the center of this cystic, inflamed tissue, a small 0.5- to 1-cm white cyst containing long hair growth was noted (Figure 3). The cystic tissues were swabbed for culture. Once the affected tissues were removed, débridement of the remaining affected subcutaneous tissue was performed, followed by copious lavage. Two 1/4-in Penrose drains were placed in the resection defect. Subcutaneous and dermal closure was performed.
Figure 3. The resected cystic tissues, including an inner dermoid cyst with haired contents.
Postoperative analgesia (0.05 mg/kg hydromorphone every four to six hours), antibiotics (30 mg/kg cephalexin given orally every 12 hours), and crystalloid intravenous maintenance fluids were administered. The dog was discharged from the hospital the morning after surgery, and the drains were removed four days after surgery. Skin staples were removed 11 days after surgery, and the patient came in for rechecks one month and 13 months after surgery. The patient healed well from surgery and showed no sign of cyst recurrence.