Pilomatrixoma or a “hair line fracture”
Pilomatrixomas are benign neoplasms of the ectodermal hair follicles which typically appear as solitary, firm, asymptomatic nodules1. When multiple, they may be associated with other diseases. Although pilomatrixomas are found in any age group, they occur mostly in children or in the first two decades of life. 50% arise from head and neck region, 40% before the age of 10, and 10% occur in limbs2. A 3:2 female: male incidence ratio is found. The prognosis is typically good and the treatment of choice is surgical removal. Recurrence is rare.
An 11-year-old was referred to the Orthopaedic clinic following a fall. X-rays identified a fracture of the distal third of his left radius with a non-adjacent calcified body. On examination, a mildly tender, palpable, subcutaneous swelling over the dorsal aspect of his forearm measuring about 6mm with normal overlying skin was noted. He was otherwise healthy and had received all his immunisations.
Manipulation under anaesthesia in theatre and an open biopsy of the forearm mass were performed. Histological appearances were consistent with an ossified pilomatrixoma (calcified epithelioma of Malherbe) with no evidence of dysplasia or malignancy. Postoperative recovery was uneventful. Malherbe and Chenantais first described a pilomatrixoma in 1880 as a benign tumour commonly found in children thought to originate from the sebaceous glands. In 1961 Forbis and Helwig discovered that the cell of origin is the outer sheath cell of the hair follicle.3 Patients are usually asymptomatic but pain, inflammation and ulceration have been reported, particularly in the multifocal type of pilomatrixomas.
It is the most common superficial skin tumour primarily affecting children and adolescents. Peak incidence is between the ages of 8 and 13 years3. Sizes in diameter can range from 0.5 to 3 cm. The largest case series in the literature includes 346 pilomatrixomas of which 15.3 per cent were observed in the upper extremities4. Other cases have been reported including pilomatrixoma of the pinna of the ear, breast, head and neck. Pilomatrixomas can be associated with other conditions such as Gardner’s syndrome, myotonic muscular dystrophy, Xeroderma Pigmentosum and basal cell nevus syndrome. Differential diagnoses include a lipoma, dermoid cyst, foreign body or an atheroma. Management is with an excision biopsy.
The histological picture depends on the stage of tumour development. There is often multi focal dystrophic calcification surrounded by shadow cells or (ghost cells), of keratinizing squamous epithelium with basaloid cells in the periphery. Calcification is sometimes seen. A spontaneous regression of a pilomatrixoma has never been observed. There have been a few cases where such lesions have turned malignant. These lesions are usually found in middle-aged patients.
Pilomatrixomas, as illustrated in our case, can add confusion to the management of a co-existing disease or injury. Histological examination is required for definitive diagnosis. They should be considered as a differential diagnosis in any cutaneous lesions, particularly in children and adolescents.
K Ramotshabi, T M Connelly, M Mullins, JKelly, P O’Grady
Division of Trauma and Orthopaedic Surgery
Mayo General Hospital
Castlebar, Co. Mayo
Tara Connelly, Division of Trauma and Orthopaedic Surgery, Mayo General Hospital, Castlebar, Co. Mayo
- Lever WF, Griesemer RD. Calcifying epithelioma of Malherbe; report of 15 cases, with comments on its differentiation from calcified epidermal cyst and on its histogenesis. Archives of dermatology and syphilology. 1949;59:506-518.
- Cigliano B, Baltogiannis N, De Marco M, Faviou E, Settimi A, Tilemis S, Soutis M, Papandreou E, D’Agostino S, Fabbro MA. Pilomatricoma in childhood: a retrospective study from three European paediatric centres. European journal of pediatrics. 2005;164:673-677.
- Forbis R, Jr., Helwig EB. Pilomatrixoma (calcifying epithelioma). Archives of dermatology. 1961;83:606-618.
- Pirouzmanesh A, Reinisch JF, Gonzalez-Gomez I, Smith EM, Meara JG. Pilomatrixoma: a review of 346 cases. Plastic and reconstructive surgery. 2003;112:1784-1789.