Pilomatricoma

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Pilomatricoma

BASICS

DESCRIPTION

No known risk factors

Although uncommon, multiple pilomatricomas have been associated with the following conditions:

Initial Tests (lab, imaging)

11 Hills SE, Maddalozzo J. Congenital lesions of epithelial origin. Otolaryngol Clin North Am. 2015;48(1):209 " 223.22 Pant I, Joshi SC, Kaur G, et al. Pilomatricoma as a diagnostic pitfall in clinical practice: report of two cases and review of literature. Indian J Dermatol. 2010;55(4): 390 " 392.33 Hassanein AM, Glanz SM, Kessler HP, et al. Beta-catenin is expressed aberrantly in tumors expressing shadow cells. Pilomatricoma, craniopharyngioma, and calcifying odontogenic cyst. Am J Clin Pathol. 2003;120(5):732 " 736.44 Kim IH, Lee SG. The skin crease sign: a diagnostic sign of pilomatricoma. J Am Acad Dermatol. 2012;67(5):e197 " e198.55 Hwang JY, Lee SW, Lee SM. The common ultrasonographic features of pilomatricoma. J Ultrasound Med. 2005;24(10):1397 " 1402.66 Ieni A, Todaro P, Bonanno AM, et al. Limits of fine-needle aspiration cytology in diagnosing pilomatrixoma: a series of 25 cases with clinico-pathologic correlations. Indian J Dermatol. 2012;57(2):152 " 155.

Benign, adnexal skin tumor derived from hair matrix cells
Slow-growing, hard, typically solitary nodule found in the dermis/subcutaneous layer of the skin
Most commonly occurs on the head and neck of children and young adults (1)
Variants:Pilomatrix carcinoma, a rare malignant variant, can be locally invasive and have a high recurrence rate. Infrequent cases of metastases have been reported.Perforating pilomatricoma
Synonym(s): pilomatrixoma; calcifying epithelioma of Malherbe; trichomatricoma
System(s) affected: integumentary

Pilomatrix carcinoma, a rare malignant variant, can be locally invasive and have a high recurrence rate. Infrequent cases of metastases have been reported.
Perforating pilomatricoma

EPIDEMIOLOGY

Pilomatricoma was first described in 1880 by Malherbe and Chenantais (2).
Incidence of pilomatricomas has not been well studied.
One study reported an incidence of 1.04% of all benign skin tumors examined and 0.08% of all histologic samples reviewed.
Slight female preponderance (male-to-female ratio, 1:1.1).
Most frequently occurs in patients <20 years old (37 " 46%), with some reports of a second smaller peak in the 5th to 7th decades of life.
Pilomatrix carcinoma is more common in males and the elderly but is extremely rare, with <80 total cases reported.

ETIOLOGY AND PATHOPHYSIOLOGY

Pilomatricomas derive from the primitive basaloid cells of the epidermis that differentiate into hair matrix cells with uncontrolled proliferation in the dermis/subcutaneous tissue.
There are anecdotal reports of lesions arising in areas of trauma, insect bites, and surgery (3.9% of cases).

Activating ²-catenin gene (CTNNB1) mutations are thought to play an important role.
A high level of ²-catenin results in the stimulation of cellular proliferation and/or inhibition of cell death. (3).

RISK FACTORS

COMMONLY ASSOCIATED CONDITIONS

Myotonic dystrophy
Turner syndrome
Rubinstein-Taybi syndrome
Trisomy 19
Sotos syndrome
Gardner syndrome

DIAGNOSIS

HISTORY

Usually asymptomatic
Some patients may complain of mild tenderness or pain secondary to palpation, pruritus, or inflammation.

PHYSICAL EXAM

Most frequently located on the head and neck (54 " 73%) but may also appear on an upper limbs (23 " 26%), lower limbs (14%), or trunk
Typically presents as a solitary, well-circumscribed, mobile, firm dermal or subcutaneous nodule
Skin overlaying the lesion usually has a normal appearance but may have a pink or bluish hue or may become semitransparent, atrophic, or ulcerate.
Ranges in size from 1 to 50 mm, although most commonly ≤15 mm.
The "tent sign " is assessed for by stretching the overlaying skin taut, revealing the irregular contours of the nodule.
The "teeter-totter sign " is elicited by pressing on one edge of the lesion which causes the opposite edge to protrude from the skin (2).
The "skin crease sign " is elicited by squeezing the edge of the nodule with both thumbnails, perpendicular with the skin tension line, which appears to be helpful with preoperative diagnosis (4).
Calcium may be visible through the surface as yellow or white flecks.

DIFFERENTIAL DIAGNOSIS

Sebaceous cyst
Epidermoid cyst
Dermoid cyst
Neurofibroma
Foreign body reaction
Calcified hematoma
Calcified lymph node
Vascular lesion
Basal cell carcinoma
Squamous cell carcinoma
Fat necrosis
Nonspecific cyst

DIAGNOSTIC TESTS & INTERPRETATION

The diagnosis of pilomatricoma is predominately made clinically and confirmed by pathology.
The correct preoperative diagnosis of pilomatricoma by physicians is relatively low (28 " 46%).

Use of radiography, CT, ultrasound, and MRI to aid with diagnosis has been reported, but they are not used routinely.
Ultrasound may be used as a noninvasive option that may show a well-defined mass with inner echogenic foci and a peripheral hypoechoic rim or a completely echogenic mass with strong posterior acoustic shadowing in the subcutaneous layer (5).

Punch biopsy
Fine-needle aspiration cytology has been described as a relevant preoperative diagnostic procedure for masses in the head and neck; however, care must be taken to avoid misdiagnosing pilomatricoma as a malignant lesion (6).
Pilomatricomas have been shown to appear as a dark mass using otoscope transillumination, which may aid in preoperative diagnosis.

Histologically, pilomatricomas are well-circumscribed and encapsulated masses filled with palisading basaloid cells and islands of eosinophilic "shadow " or "ghost " cells and are frequently associated with a foreign body giant cell reaction and dystrophic calcification.
Bony metaplasia, hemosiderin, and melanin deposition may also be present.
Pilomatrix carcinoma is indicated by the presence of pleomorphic cells, increased atypia and mitotic figures, central necrosis, and local infiltration of blood vessels and soft tissue.

TREATMENT

Treatment of choice is simple excision with minimal margins.
Pilomatricomas do not spontaneously regress; however, perforating pilomatricomas may extrude spontaneously.
Skin grafts may be necessary to cover the area of resection, depending on the volume removed and the degree of adherence to the epidermis.

ONGOING CARE

COMPLICATIONS

REFERENCES

ADDITIONAL READING

Barreto-Chang OL, Gorell ES, Yamaguma MA, et al. Diagnosis of pilomatricoma using an otoscope. Pediatr Dermatol. 2010;27(5):554 " 557.
Guinot-Moya R, Valmaseda-Castellon E, Berini-Aytes L, et al. Pilomatrixoma. Review of 205 cases. Med Oral Patol Oral Cir Bucal. 2011;16(4):e552 " e555.
Hassanein AM, Glanz SM. Beta-catenin expression in benign and malignant pilomatrix neoplasms. Br J Dermatol. 2004;150(3):511 " 516.
Kumaran N, Azmy A, Carachi R, et al. Pilomatrixoma " accuracy of clinical diagnosis. J Pediatr Surg. 2006;41(10):1755 " 1758.
Marrogi AJ, Wick MR, Dehner LP. Pilomatrical neoplasms in children and young adults. Am J Dermatopathol. 1992;14(2):87 " 94.
O 'Connor N, Patel M, Umar T, et al. Head and neck pilomatricoma: an analysis of 201 cases. Br J Oral Maxillofac Surg. 2011;49(5):354 " 358.
Ohnishi T, Nakamura Y, Watanabe S. Perforating pilomatricoma in a process of total elimination. J Am Acad Dermatol. 2003;49(2)(Suppl Case Reports):S146 " S147.
Price HN, Zaenglein AL. Diagnosis and management of benign lumps and bumps in childhood. Curr Opin Pediatr. 2007;19(4):420 " 424.
Tselis N, Heyd R, Vogt HG, et al. Pilomatrix carcinoma with lymph node and pulmonary metastases. Strahlenther Onkol. 2006;182(12):727 " 732.

CODES

ICD10

D23.9 Other benign neoplasm of skin, unspecified
D23.30 Other benign neoplasm of skin of unspecified part of face
D23.4 Other benign neoplasm of skin of scalp and neck
D23.39 Other benign neoplasm of skin of other parts of face

ICD9

216.9 Benign neoplasm of skin, site unspecified
216.3 Benign neoplasm of skin of other and unspecified parts of face
216.4 Benign neoplasm of scalp and skin of neck

SNOMED

CLINICAL PEARLS

Pilomatricoma is a benign, relatively infrequent, slow-growing, adnexal skin tumor.
Most frequently reported in children and young adults
Typically appears as a solitary, firm, asymptomatic nodule beneath the skin
The "tent sign " and "teeter-totter sign " are helpful clinical clues.
Diagnosis is made by histology. Imaging is limited.
Treatment of choice is simple excision.