A rare convergence: Unveiling the uncommon presentation of trichoblastic carcinoma with cylindroma – A singular case report

Abstract

Trichoblastic carcinoma is an infrequent and malignant neoplasm of cutaneous adnexal origin, arising subsequent to follicular differentiation. Clinically, it manifests as a well-circumscribed, solitary lesion, predominantly observed on the scalp. Cylindroma, conversely, is a benign and indolent adnexal tumor, with a predilection for the scalp, head, neck, and trunk, exhibiting a higher incidence in females.A 54-year-old female presented with a 2 cm swelling on the left anterior chest wall, which had progressively enlarged over the course of one month, accompanied by severe pain and mild pruritus. Her family and surgical histories were unremarkable, and clinical examination yielded no significant findings. The initial diagnosis of an infected sebaceous cyst was reconsidered following FNAC, which suggested a granulomatous lesion. Biopsy revealed a 2 cm globular mass containing yellowish-white material.Microscopic examination disclosed highly pleomorphic basaloid and malignant stromal cells arranged in an irregular pattern, along with a cylindromatous component exhibiting the characteristic jigsaw pattern. Immunohistochemical (IHC) analysis demonstrated strong PanCK and EMA positivity, leading to a final diagnosis of trichoblastic carcinoma with coexisting cylindroma.Trichoblastic carcinoma, a rare malignant cutaneous adnexal tumor, originates from the external root sheath of the hair follicle. Key histological features include highly pleomorphic basaloid and stromal cells with densely packed, hyperchromatic nuclei and abundant mitotic activity. Cylindromas may present as solitary or multiple lesions, though their histogenesis, whether apocrine or eccrine, remains ambiguous. Notable characteristics include a biphasic cell population arranged in a jigsaw pattern.