CLINICAL HISTORY:

Signs and symptoms:  A 19 year old male presented with a pink, shiny 3 cm protuberant nodule on his right upper extremity that grew rapidly over 2 months.

Previous Treatment:  tea tree oil

Other information:  none

PHYSICAL EXAM:

Solitary 3.2cm well circumscribed, shiny pink nodule on right upper arm that is hard and slightly painful upon palpation. (figure 1)

Figure 1

LABORATORY TESTS:

none

DERMATOHISTOPATHOLOGY:

Histopathological examination (see figures 2 and 3) showed sections of nests of cells, some of which presented with a basaloid appearance with regular crowded oval nuclei. There were also associated ghost cells with residual eosinophilic cytoplasm and without preserved nuclei. Scattered chronic inflammatory cells along with multinucleated giant cells and a focus of calcification was present. No evidence of malignancy was identified.

Figure 2

Figure 3

DIFFERENTIAL DIAGNOSIS:

1.   Dermatofibrosarcoma protuberans
2.   Pilomatricoma / pilomatrical carcinoma
3.   melanoma
4.   SCC
5.   BCC

SCROLL DOWN FOR ANSWER AND DISCUSSION.

CORRECT DIAGNOSIS:

Pilomatricoma

DISCUSSION:

Pilomatricoma is a benign skin neoplasm that can exhibit wide protean manifestations, appearing most commonly as a solitary, deep-seated, firm nodule with a normal to semi-transparent epidermis. Occasionally, they can be superficial and exhibit a faint red to blue appearance, with deposits of calcium eroded through the skin surface. (1) Graham and Merwin described the “tent sign” as part of the clinical exam to visualize the multifaceted nature of the mass, which is elicited by stretching the skin over the tumor. (2) There are other variants reported including lymphangiectatic, anetodermic and ulcerated. (1) The tumor usually varies in diameter from 0.5 to 3.0 cm, with the largest reported case measuring 20 cm. (3) Pilomatricomas appear most commonly on the head and neck, then upper extremities, and rarely on the trunk or lower extremities. (4) Noguchi et al suggested that the distribution of pilomatricoma corresponds to the density of hair follicles at a particular site. (5) There is a bimodal distribution, in children and adults over 60 years of age, with preponderance in females. (1)
There have been reports of pilomatricomas appearing in association with myotonic dystrophy (6), Gardner’s syndrome (7), and beta-catenin mutations (8). Cases of pilomatricomas associated with hypercalcemia and elevated levels of parathyroid hormone-related protein have also been described. (3)
The histological presentation of pilomatricomas are sharply demarcated, and often surrounded by a connective tissue capsule. They are located in the lower dermis and can extend into the subcutaneous fat. Characteristic features pilomatricomas include irregularly shaped island of epithelial cells embedded in a cellular stroma. These islands contain two main cells populations: 1) basophilic cells that display deeply basophilic nuclei which lie close together and have scanty cytoplasm, and 2) shadow or ghost cells, that have a distinct border and possess a central unstained area as a shadow of the lost nucleus. (9) Calcium deposits are found in approximately 75% of tumors and can be confirmed with the von Kossa stain. (10)
Pilomatricomas are often clinically misdiagnosed, although they are not exceedingly rare, with an incidence rate reported as one of every 500 specimens. (1) Differentials may depend on location, age, and appearance of the nodule. (11) Preoperative diagnoses most commonly include epidermoid cyst, followed by malignancy, inclusion dermoid cyst, and hemangioma. (1)
Fine needle aspiration has been used as a diagnostic tool; however, accurate cytodiagnosis and cytological distinction from other cutaneous lesions, both benign and malignant, remains a challenge. (12) Ultrasonography can be helpful when evaluating tumors in the parotid or breast area. (4) Recurrences, although they do occur (13), are low.

TREATMENT:

Complete surgical excision remains the treatment of choice for benign pilomatricomas.

REFERENCES:

1) Julian CG, Bowers PW. A clinical review of 209 pilomatricomas. J Am Acad Dermatol. Aug 1998;39(2 Pt 1):191-5.
2) Graham JL, Merwin CF. The tent sign of pilomatricoma. Cutis. Nov 1978;22(5):577-80.
3) Kambe Y, Nakano H, Kaneko T, Aizu T, Ikenaga S, Harada K, Nakajima N, Moritsugu R, Hanada K. Giant pilomatricoma associated with hypercalcaemia and elevated levels of parathyroid hormone-related protein. Br J Dermatol 2006;155:208-10.
4) Pirouzmanesh A, Reinisch JF, Gonzalez-Gomez I, Smith EM, Meara JG. Pilomatrixoma: a review of 346 cases. Plast Reconstr Surg. Dec 2003;112(7):1784-9.
5) Noguchi H, Hayashibana T, Ono T. A statistical study of calcifying epithelioma, focusing on the site of origin. J Dermatol 1995;22:24-7.
6) Harper PS. Calcifying epithelioma of Malherbe. Association with myotonic muscular dystrophy. Arch Dermatol. Jul 1972;106(1):41-4.
7) Leppard BJ, Bussey HJ. Gardner's syndrome with epidermoid cysts showing features of pilomatrixomas. Clin Exp Dermatol. Mar 1976;1(1):75-82.
8) Chan, EF. Pilomatricomas contain activating mutations in B-catenin. J Am Acad Dermatol. 43:701, 2000.
9) Elder D, Elenitsas R, Ragsdale BD. Tumors of the epidermal appendages. In: Elder D, Elenitsas R, Jaworsky C, Johnson B Jr, editors. Lever’s histopathology of the skin, 8th edition. Philadelphia: Lippincott-Raven, 1997: p747-803.
10) Peterson WC Jr, Hult AM. Calcifying epithelioma of Malherbe. Arch Dermatol 1964;90:404.
11) Macleod AJ, Scobie WG. Pilomatrixoma as a diagnostic problem: the Edinburgh experience. J R Coll Surg Edinb. 1991 Aug;36(4):261-3.
12) Wang J, Cobb CJ, Martin SE, Venegas R, Wu N, Greaves TS. Pilomatrixoma: clinicopathologic study of 51 cases with emphasis on cytologic features. Diagn Cytopathol 2002;27:167–72.
13) Aslan G, Erdogan B, Aköz T, Görgü M, Seçkin S, Terzioglu A. Multiple occurrence of pilomatrixoma. Plast Reconstr Surg. Sep 1996;98(3):510-3.

Additional Comment:

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