A 69-Year-Old Woman with an Occipital Giant Proliferating Trichilemmal (Pilar) Cyst Treated with Surgical Resection

Introduction

Adnexal tumors are a heterogeneous group of skin neoplasms originating from pilosebaceous units and sweat glands. Among these, proliferating trichilemmal cysts (PTCs) are rare benign lesions derived from the outer root sheath of the hair follicle, most commonly found on the scalp of older women. Clinically, they typically present as slow-growing, firm, and superficial nodules. Histologically, these cysts have a lobular structure, produce a type of keratin typical of hair follicles (trichilemmal keratinization), and show increased growth of skin cells, and they lack the usual granular layer seen in normal skin. Although generally benign, rare cases of malignant transformation have been reported. Early diagnosis and complete surgical excision remain the mainstays of treatment to prevent local complications and recurrence [1].

Case Report

HISTOLOGICAL EXAMINATION:

Histopathological analysis revealed trichilemmal keratinization characteristic of pilar cysts, with irregularly contoured lobular-cystic morphology and calcified areas. A foreign body-type reaction to keratin was observed sporadically (Figure 7). Focal invasion into the deep dermis and subcutaneous tissue was noted. Low-grade nuclear atypia and focal mitosis were observed (Figures 7, 8). The tumor, measuring 15×12×7.5 cm, had intact surgical margins. No perineural or lymphovascular invasion was observed. High-grade atypia and atypical mitosis were absent, and no necrosis was detected. According to the classification criteria proposed by Ye et al, the tumor was classified as Group 2. The irregular borders and invasion into the deep dermis and subcutaneous adipose tissue supported this classification [1].

Discussion

This case report contributes to the current understanding of proliferating trichilemmal cysts by highlighting the clinical and surgical challenges posed by giant lesions, particularly those involving the occipital region. Unlike typical pilar cysts, which are often small and asymptomatic, this case demonstrates how neglected lesions can attain significant size, necessitating advanced reconstructive techniques. The chronic growth history, absence of overt malignancy, and successful use of local and regional flaps offer valuable insights into diagnostic differentiation and surgical planning for similar tumors. Moreover, the report emphasizes the necessity of a multidisciplinary approach, integrating pathology, imaging, and reconstructive surgery for optimal outcomes in extensive adnexal neoplasms.

Proliferating pilar tumors (PPTs) are most commonly seen in postmenopausal women, particularly those over the age of 60 [2,3]. This sex- and age-related pattern may be influenced by hormonal and biological changes that occur after menopause, which are thought to play a role in the development of these tumors. Interestingly, PPTs are rarely seen in bald individuals, likely because these tumors originate from hair follicle structures, which are absent in bald areas. Since baldness is far more common in men than in women, this may partly explain why women tend to develop PPTs more often. These trends highlight how factors like age and hair follicle density can help us better understand who is more at risk. [4].

When PPTs exhibit prolonged growth, necrosis, and calcification within the tumor can occur due to impaired blood supply [5]. As these tumors increase in size, the risk of malignant transformation also rises, necessitating lymph node dissection in such cases. In our case, the enlarged lymph node was evaluated as reactive [6].

In a study by Je Nappi involving 76 patients, PPTs were histopathologically classified into 3 grades. Based on histopathological findings, our case was classified as Grade 2, which have a 15% risk of recurrence [1].

While Alam et al emphasized the diagnostic challenge in differentiating PTC from squamous cell carcinoma due to ulceration and rapid growth, our case exhibited no such clinical ambiguity, as the lesion lacked ulcerative features and resembled neither an epidermoid cyst nor a malignant cutaneous tumor. The lesion in their report was excised without the need for advanced reconstructive techniques. In contrast, our case required a 2-stage closure involving a local rotation flap and a supraclavicular artery island flap, highlighting the importance of reconstructive planning in large tumors [7].

Although these tumors are known for their recurrence rates, close and extended follow-up remains crucial to catch any signs of regrowth or progression early. When recurrence does occur, it can be clinically challenging, sometimes suggesting a more aggressive course. For that reason, regular monitoring plays a key role, not just in spotting recurrence, but also in allowing timely intervention when needed. This kind of careful follow-up helps manage complications more effectively and supports better overall outcomes for the patient [8].

In this case, CT imaging proved particularly useful in assessing the tumor’s characteristics. The scan did not reveal any signs of bone invasion or resorption, which supported the initial impression of a benign lesion. These radiological features suggested aggressive tumor behavior, as malignant tumors often infiltrate and destroy surrounding bone structures, in contrast to benign lesions, which typically exhibit more localized growth patterns without significant bone destruction [2]. In significant defects, partial necrosis of the local rotation flap highlights the need for alternative reconstruction methods [9]. The necrotic area presents a considerable risk of infection, which can complicate the healing process. To reduce this risk and promote optimal wound healing, topical 1% gentamicin was applied following surgical debridement. This approach helps control infection and supports tissue repair, facilitating the progression of secondary wound healing [10]. Following removal of the rotation flap, a defect was created in the neck, which was reconstructed using a supraclavicular fascio-cutaneous flap [11].

Conclusions

Proliferating trichilemmal cysts are a rare subset of benign scalp tumors with the potential for extensive growth and, in some cases, malignant transformation. This case, involving a 69-year-old woman with a giant occipital lesion, illustrates the importance of early recognition, thorough radiologic and histopathologic assessment, and a tailored surgical approach to achieve complete resection and functional reconstruction. The use of combined flap techniques in a vascular-rich area demonstrates the complexity of surgical management in advanced cases. Regular follow-up remains essential to monitor for recurrence or late-onset complications.