Unique occurrence of trichilemmal carcinoma in the scrotal skin of a giant panda: a pathological analysis

BACKGROUND: Trichilemmal carcinoma (TC) is a rare cutaneous appendage malignancy with scarce human cases and very few animal cases have been documented in the available literature, especially in giant pandas. CASE PRESENTATION: A 23-year-old male captive giant panda had 4-week scrotal hyperplasia and ulceration, with a 4.5 cm×4 cm irregular lesion and neutrophils were elevated. Pathology revealed dermal lobular/cord-like invasive atypical clear cells, squamous nests and outer root sheath cysts. PAS staining was positive. Immunohistochemistry showed Her-2 (+), CK5/6 (++), p63 (++), Ki-67 (+), CD34 (+), and p53 (+), excluding squamous cell carcinoma and trichofolliculoma. Local resection (0.8 cm margin) was done under general anesthesia. Postoperative anti-infection led to 2-week wound healing; 3-month follow-up showed no recurrence with normal behavior. CONCLUSIONS: This first reported giant panda TC with human-like immunophenotype provides evidence for managing rare animal cutaneous appendage tumors.