Giant Sebaceous Cyst of the Scalp Mimicking a Soft Tissue Tumor: A Case Study

   Abstract

Sebaceous cysts, also referred to as epidermoid cysts, are common benign cutaneous lesions arising from the pilosebaceous unit. They typically present as slow-growing, painless nodules and are most often small in size. Giant sebaceous cysts of the scalp are rare and may clinically mimic soft tissue tumors, leading to diagnostic uncertainty. We report a case of a middle-aged male presenting with a large, progressively enlarging scalp mass initially suspected to be a soft tissue neoplasm. Clinical evaluation and imaging suggested a benign cystic lesion, which was confirmed on surgical excision and histopathological examination. This case highlights the importance of considering sebaceous cysts in the differential diagnosis of large scalp masses and emphasizes the role of clinical assessment and histopathology in establishing a definitive diagnosis.

Introduction

Sebaceous cysts are among the most frequently encountered benign skin lesions in clinical practice. They arise due to obstruction of the sebaceous duct or proliferation of epidermal cells within the dermis, resulting in cyst formation filled with keratinous material [1]. Common sites include the scalp, face, neck, and trunk, areas rich in sebaceous glands.

While most sebaceous cysts are small and asymptomatic, giant variants—generally defined as lesions exceeding 5 cm in diameter—are uncommon [2]. When occurring on the scalp, giant sebaceous cysts may pose diagnostic challenges, as their size, firmness, and slow progression can resemble soft tissue tumors, lipomas, or even malignant lesions [3]. Delayed presentation is common due to their painless nature, contributing to significant enlargement over time.

This case study describes a giant sebaceous cyst of the scalp masquerading as a soft tissue tumor, underscoring the importance of accurate clinical evaluation and timely surgical management.

Patient Information

• Age / Gender: 52-year-old male

• Medical History: Hypertension, well controlled

• Medication History: Antihypertensive medications

• Surgical History: None

• Social History: Non-smoker, occasional alcohol use

• Chief Complaint: Slowly enlarging painless scalp swelling

Clinical Findings

The patient presented to the surgical outpatient clinic with a complaint of a progressively enlarging swelling over the parietal region of the scalp for approximately three years. The swelling was initially small but had gradually increased in size. There was no associated pain, discharge, redness, or history of trauma to the scalp.

On physical examination, a solitary, well-defined, dome-shaped mass measuring approximately 8 × 7 cm was noted over the right parietal scalp region. The swelling was firm, non-tender, and mobile over underlying structures, with normal overlying skin and no visible punctum. There was no local warmth, erythema, or regional lymphadenopathy. The lesion was non-pulsatile and did not transilluminate.

Based on the size and consistency, a provisional diagnosis of a benign soft tissue tumor was considered.

Timeline

• Year 0: Appearance of small scalp swelling

• Year 1–3: Gradual increase in size

• Presentation: Large, painless scalp mass

• Imaging: Ultrasound of scalp lesion

• Surgery: Elective excision of the mass

• Follow-up: Uneventful recovery

Diagnostic Assessment

Routine laboratory investigations, including a complete blood count and standard biochemical parameters, were within normal limits, with no evidence of infection, anemia, or metabolic abnormalities. These findings suggested the absence of any underlying systemic condition or inflammatory process contributing to the lesion.

Ultrasonography of the scalp demonstrated a well-circumscribed, hypoechoic cystic lesion with internal echoes, consistent with the presence of keratinous or sebaceous material, and was suggestive of a benign cystic mass. There was no evidence of internal or peripheral vascularity on Doppler assessment, and no signs of invasion into deeper tissues such as the galea aponeurotica or underlying bone. The imaging characteristics favored a diagnosis of an epidermoid or sebaceous cyst; however, given the unusually large size of the lesion and its long-standing nature, the possibility of a benign soft tissue tumor could not be definitively excluded on imaging alone.

In view of the diagnostic uncertainty and to establish a definitive diagnosis, surgical excision of the lesion was planned. Histopathological examination of the excised specimen was considered essential to confirm the nature of the lesion, exclude malignant transformation, and guide further management.

Diagnosis

Giant sebaceous cyst of the scalp mimicking a soft tissue tumor.

Therapeutic Intervention

The patient underwent elective surgical excision of the scalp mass under regional anesthesia in a controlled operative setting. After appropriate aseptic preparation and draping, a careful incision was made directly over the lesion along relaxed skin tension lines to optimize cosmetic outcome. Blunt and sharp dissection were employed to meticulously separate the cyst from the surrounding subcutaneous tissues, taking care to preserve adjacent structures. The cyst was excised completely in toto with its capsule intact, an essential step to prevent intraoperative spillage of contents and to minimize the risk of postoperative recurrence.

On gross examination, the excised mass was well defined and contained thick, whitish, keratinous material, a finding characteristic of a sebaceous (epidermoid) cyst. Adequate hemostasis was achieved throughout the procedure, following which the surgical wound was closed in layers using appropriate sutures to ensure proper wound approximation. A sterile pressure dressing was applied to reduce dead space, prevent hematoma formation, and support optimal wound healing in the postoperative period.

Follow-Up and Outcomes

The postoperative period was uneventful. The patient experienced no wound infection, hematoma, or dehiscence. Sutures were removed on postoperative day 10, with satisfactory wound healing and acceptable cosmetic outcome.

Histopathological examination revealed a cyst lined by stratified squamous epithelium filled with lamellated keratin, without evidence of dysplasia or malignancy. These findings confirmed the diagnosis of a sebaceous (epidermoid) cyst.

At follow-up visits, the patient remained asymptomatic, with no evidence of recurrence.

Discussion

Giant sebaceous cysts represent an uncommon manifestation of an otherwise frequently encountered benign cutaneous lesion. Although sebaceous and epidermoid cysts are routinely seen in clinical practice, lesions attaining a large or “giant” size are rare and may pose diagnostic challenges. The scalp is a particularly common site due to its high density of pilosebaceous units; however, cysts of significant dimensions are unusual and often prompt clinical concern for underlying neoplastic or malignant processes, especially when there is a history of progressive enlargement over a prolonged period [2,3].

The differential diagnosis of a large, slow-growing scalp mass is broad and includes benign entities such as lipoma, dermoid cyst, pilar (trichilemmal) cyst, neurofibroma, and vascular lesions like hemangioma, as well as malignant conditions including soft tissue sarcoma [4]. Certain clinical features can help favor a benign etiology, including the absence of pain or tenderness, slow and insidious growth, soft to firm consistency, mobility over underlying structures, and lack of overlying skin changes such as ulceration, erythema, or fixation. Nevertheless, these features are not always sufficient to exclude more serious pathology.

Imaging modalities play a supportive role in the evaluation of such lesions. Ultrasonography is often the initial investigation of choice, as it is noninvasive, readily available, and useful for distinguishing cystic from solid masses. Computed tomography or magnetic resonance imaging may be employed in selected cases to better define lesion extent, assess involvement of deeper tissues, and assist in surgical planning. Despite these advantages, imaging findings may not always yield a definitive diagnosis, particularly in large or atypical lesions [5].

Complete surgical excision with careful removal of the entire cyst wall remains the treatment of choice for giant sebaceous cysts. Incomplete excision or rupture of the capsule during surgery can result in residual epithelial lining and subsequent recurrence. Histopathological examination of the excised specimen is mandatory, not only to confirm the clinical diagnosis but also to exclude rare possibilities of malignant transformation or unexpected pathology [1,4]. This comprehensive approach ensures accurate diagnosis, effective treatment, and optimal long-term outcomes for the patient.

Conclusion

Giant sebaceous cysts of the scalp, though benign, can clinically mimic soft tissue tumors due to their size and presentation. A high index of suspicion, thorough clinical examination, and appropriate imaging are essential for accurate diagnosis.

Definitive management through complete surgical excision and histopathological confirmation ensures excellent outcomes with minimal recurrence. Awareness of this rare presentation can prevent misdiagnosis, alleviate patient anxiety, and facilitate timely and effective treatment.

References

1. Zito PM, Scharf R. Epidermoid cyst. StatPearls Publishing; 2023.

2. Nigam JS, et al. Epidermoid cysts: A clinicopathological analysis. J Clin Diagn Res. 2017;11(9):EC01–EC04.

3. Kamyab-Hesari K, et al. Giant epidermoid cysts: A report of three cases. Iran J Pathol. 2010;5(3):141–144.

4. James WD, Elston DM, Treat JR, Rosenbach MA. Andrews’ Diseases of the Skin: Clinical Dermatology. 13th ed. Elsevier; 2020.

5. Lee HS, et al. Imaging features of epidermoid cysts. Ultrasonography. 2015;34(3):153–161.

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