Cylindroma Pathology: Key Insights For Accurate Diagnosis

This distinctive tumour is an

adnexal tumour

argued to arise from the apocrine or eccrine secretory coil or coiled duct. Cylindromas are benign skin lesions primarily affecting the dermis, characterized by their unique histopathological appearance that aids in definitive diagnosis.

Introduction

Cylindroma is a rare benign neoplasm of the skin’s adnexal structures, most commonly presenting on the scalp, face, or neck. It can occur sporadically as solitary lesions or multiply in the context of genetic syndromes. Histopathologically, it is recognized by its hallmark ‘jigsaw puzzle’ arrangement of tumour islands surrounded by thick hyaline material. Understanding its pathology is crucial for distinguishing it from malignant mimics and related adnexal tumours.

These tumours are typically asymptomatic but can cause cosmetic concerns or pain when numerous, as seen in ‘turban tumours’. While generally benign, rare malignant transformations to cylindrocarcinoma have been reported, particularly in larger lesions.

Clinical Features

Cylindromas often present as firm, pink to red nodules or dome-shaped papules, predominantly on the scalp. Solitary lesions are common in sporadic cases, measuring 0.5–2 cm in diameter. Multiple cylindromas form the ‘turban tumour’ appearance when they coalesce across the scalp.

In hereditary settings, such as Brooke-Spiegler syndrome or familial cylindromatosis, patients develop numerous tumours starting in adolescence or early adulthood. These syndromes are autosomal dominant, linked to mutations in the

CYLD

gene on chromosome 16q12, which acts as a tumour suppressor involved in NF-κB signaling regulation. Affected individuals may also develop spiradenomas and trichoepitheliomas, complicating clinical diagnosis without biopsy.

Histopathology

Low Power View

At low magnification, cylindroma appears as a

non-encapsulated tumour nodule

arising from the dermis (Figure 1, not shown). It is composed of multiple irregular tumour islands arranged in a characteristic

‘jigsaw’ pattern

(Figure 2). This pattern arises from the interlocking borders of the islands, mimicking a puzzle.

Surrounding the tumour islands and interspersed as discrete droplets within the nodules is a thick

hyaline deposit

(Figure 3). These deposits create a lattice-like framework that is a diagnostic hallmark.

Cellular Composition

Two distinct cell populations comprise the tumour nodules:

• Smaller peripheral cells**: Hyperchromatic nuclei, scant cytoplasm, arranged at the periphery of islands.
• Larger central cells**: Open vesicular nuclei, pale cytoplasm, predominant in the island centers.

This bimorphic pattern reflects differentiation towards ductal structures, with peripheral cells resembling basal/myoepithelial cells and central cells akin to secretory cells.

Stromal and Special Stains

The hyaline bands and deposits are

PAS-positive and diastase-resistant

, confirming their glycoprotein nature. Immunohistochemistry reveals type IV and VII collagen within these sheaths. Tumour cells express cytokeratins (e.g., CK5/6, CK7), p63 in peripheral cells, and S100-positive dendritic cells scattered throughout, distinguishing it from inflammatory infiltrates.

Electron microscopy, though rarely needed, shows desmosomes and myoepithelial features supporting adnexal origin.

Cytology

Cytologically, aspirates show uniform small cells with hyperchromatic nuclei in clusters, embedded in hyaline material. However, biopsy is preferred for architecture assessment.

Pathogenesis

The exact cell of origin remains debated: apocrine vs. eccrine secretory coil or coiled duct. Evidence favors apocrine differentiation due to shared features with spiradenomas and CYLD mutations affecting Wnt/β-catenin and NF-κB pathways, promoting tumourigenesis.

In Brooke-Spiegler syndrome, germline CYLD mutations lead to biallelic inactivation in tumours, akin to the two-hit hypothesis. Over 51 mutations are reported across diverse ethnicities.

Associated Conditions

Brooke-Spiegler syndrome and multiple cylindromatosis (turban tumour syndrome): No histopathological differences from sporadic cylindromas. Overlap tumours with eccrine spiradenoma features (spiradenocylindroma) occur. CYLD cutaneous syndrome encompasses these, with onset in the 2nd–3rd decade.

Differential Diagnosis

Key mimics include:

Tumour	Key Distinguishing Features
Eccrine spiradenoma	Diffuse basophilic proliferation without discrete islands; lymphocytic infiltrate prominent; lacks jigsaw pattern. S100 dendritic cells less vs. lymphocytes.
Spiradenocylindroma	Hybrid: combines cylindroma islands with spiradenoma’s dense basophilia and vascularity.
Trichoblastoma/Merkel cell carcinoma	Lacks hyaline sheaths; different immuno (CK20+ in Merkel).
Basal cell carcinoma	Peripheral palisading, retraction artifact, epidermal connection.
Cutaneous lymphadenoma	Lobular basaloid with dense lymphocytic infiltrate, no hyaline.

Rarely, cylindrocarcinoma shows atypia, mitoses, necrosis.

Imaging and Further Tests

Dermoscopy shows arborizing vessels or white structures. MRI useful for extensive turban tumours planning excision. Genetic testing for CYLD confirms syndromes.

Management

Observation for small asymptomatic lesions. Surgical excision for solitary or symptomatic tumours. CO2 laser or electrosurgery for multiples. In syndromes, monitor for malignancy (rare <1%). No systemic therapy; genetic counseling recommended.

Frequently Asked Questions (FAQs)

Is cylindroma malignant?

Benign; rare malignant transformation to cylindrocarcinoma in large or syndromic cases.

What causes multiple cylindromas?

Often Brooke-Spiegler syndrome or familial cylindromatosis due to CYLD mutations.

How is cylindroma diagnosed?

Skin biopsy showing jigsaw islands with hyaline sheaths.

Can cylindromas be treated without surgery?

Laser ablation or electrosurgery for superficial lesions.

Are cylindromas painful?

Usually not; multiple scalp lesions may cause discomfort from size.

Prognosis

Excellent for benign cylindromas; recurrence rare post-excision. Syndromic patients require lifelong surveillance.