Pilomatrixoma on Left Eyebrow

Pilomatrixoma (Calcified Epithelioma of Malherbe) - Definition, Diagnosis, Treatment

A 12-year-old female patient presented with a painless mass lesion growing near the outer edge of her left eyebrow in the last 3 months. The lesion was surgically removed under local anesthesia. The patient was diagnosed as Pilomatrixoma (calcified epithelioma of Malherbe) as a result of histopathological examination report.

What is the Pilomatrixoma?

Definition

Pilomatrixoma or Malherbe tumor is a benign, calcified adnexal tumor originating from the matrix of the hair follicle. Generally, it can be seen as a deep subcutaneous or superficial nodule in the head, neck and upper extremities and it usually occurs in the first two decades of life. Clinically it can be confused with various benign and malignant skin lesions. Recurrence after tumor removal is rare.

Pilomatrixomas are lesions that are frequently encountered by ear, nose and throat docrors and are often encountered by dermatologists. The incidence (0.03% -0.1%) was reported differently in each study.

The majority of pilomatrixomas (40-77%) are located in the head and neck region; This region is followed by the upper extremity and trunk. The neck is most commonly found in the neck, frontal, temporal, periorbital and preauricular areas. They are mostly solitary masses in subcutaneous tissue, smooth surface, mobile but adhering to the skin, slowly growing, generally painless, size between 0.3-5cm, which may cause slight discoloration on the skin. Multiple pilomatrixoma cases have been reported between 2-10%. Multiple or familial pilomatrixoma cases have been associated with myotonic dystrophy, Gardner syndrome, Steinert disease, Turner syndrome and sarcoidosis. Although trauma and infection may play a role in its etiology, it is not known and it is reported that pilomatrixomas may develop as a result of a pause in the cycle of hair follicles. In the present case, no etiologic factors were identified. Mutation of beta-catenin mutation in the 3p22-p21.3 gene locus was detected in 75% of pilomatrixomas, but the exact role is unknown.

Nomenclature of pilomatrixoma tumor

Pilomatrixoma or Malherbe tumor is a benign, calcified, soft tissue tumor originating from the matrix of the hair follicle. This tumor was first described by Malherbe and Chenantais in 1880 as a calcified tumor of sebaceous glands. In 1949, Lever made a histological description of this tumor and showed that pilomatrixoma originated from the matrix cells of the hair follicle. In 1961, Forbis and Helwig named this tumor pilomatrixoma.

Diagnosis of Pilomatrixoma


Although computed tomography, magnetic resonance imaging and ultrasonography may be preferred for radiological differential diagnosis, pilomatrixoma does not have any significant pathognomonic features. Computed tomography showed a calcified area under the skin; magnetic resonance imaging (T2), which shows high signal bands in the T2 sequence and internal reticulation and patch areas within the mass.

It is stated that FNAB may be helpful in the differential diagnosis especially in pilomatrixoma cases in the head and neck region. The presence of ghost cells, calcium deposits, nucleated squamous cells, foreign body giant cells and basaloid cells in the aspiration material is diagnostic. However, even experienced cytologists can mistakenly diagnose carcinoma.

Histopathologically, pilomatrixomas consist of well organized cell islands. On these islands, basaloid cells with preserved nuclei in the periphery and ghost or shadow cells in the center are arranged in a circular manner. The transitional cells between these two cell groups are apoptotic cells that will turn into ghost cells. Ghost cells are formed as a result of the keratinization of the basaloid cells and with the age of the lesion the number of ghost cells increases, the basaloid cells may disappear completely. Granulomatous inflammation, foreign body giant cells and calcification are common findings in pilomatrixomas.

Differential Diagnosis of Pilomatrixoma

calcified epithelioma of Malherbe, Eyebrow mass, Pilomatrixoma

Differential diagnosis of pilomatrixoma in the head and neck region include sebaceous cyst, ossified hematoma, branchial debris, preauricular sinus, adenopathy, chondroma, giant cell tumor, dermoid cyst, degenerate fibroxanthoma, foreign body reaction. In particular, preauricular masses can be confused with tumors or inflammatory conditions arising from the superficial lobe of the parotid gland as in our case. Because many clinicians do not think of it as a diagnosis, the rate of accurate diagnosis with clinical findings is between 0-30%.

Treatment of Pilomatrixoma

Treatment of pilomatrixomas is total excision. Generally no recurrence is observed when the tumor is totally excisedDue to its location, pilomatrixoma may cause confusion in diagnosis, especially in the branchial cleft remains. Pilomatrixoma should be remembered in skin lesions in children, since complete removal of the lesion after complete differential diagnosis provides complete recovery. Recurrence of pilomatrixomas with a low risk of malignant transformation is also rare (0-3%). Pilomatrix carcinoma should be considered when total excised pilomatrixomas are repeated.

Histopathological report and image

In the examination of the sections, calcification and ossification areas are observed in benign neoplastic lesion consisting of Ghost cells which have lost their nuclei.
Murat Enoz, MD, Otorhinolaryngology, Head and Neck Surgeon - ENT Doctor in Istanbul

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