The lesion on this 8-year-old girl’s face was first noted about a year ago. Recently, however, it has started to grow, prompting her parents to consult the child’s primary care provider (PCP). The lesion is completely asymptomatic but nonetheless concerning to the parents and to the PCP, who has no idea what it could be. He therefore refers them to dermatology.
The child is otherwise healthy. There is no family history of chronic or inheritable disease.
The lesion is a 2-cm subcutaneous firm round mass located along the superior aspect of the right jawline. The only overlying skin change is a bluish discoloration. No surface punctum is seen. No other lesions are seen or felt on examination of the rest of the head and neck.
What is the diagnosis? DISCUSSION
These findings are typical of pilomatricoma, a rather unusual lesion with multiple alternate names (among them: calcifying epithelioma of Malherbe and pilomatrixoma). These benign tumors arising from hair matrix cells are typically seen on the head, face, neck, and upper extremities, most often on children.
This patient’s lesion was typical in size, although they can vary from 3 mm (the smallest I’ve seen) to more than 20 cm. The firm feel, lack of a punctum (which would suggest an epidermal cyst), and bluish discoloration are all typical features.
These lesions generally merit little or no concern. However, in the rare instance when the patient has multiple lesions, the possibility of at least two conditions should be considered: Gardner disease and myotonic seizure.
In terms of treatment, pilomatricoma can be safely left alone; understandably, though, most parents will only be satisfied by excision. It is important to note that, unlike most true cysts, pilomatricomas have a very poorly defined cyst wall with contents that are equally odd—watery and full of tiny white flecks that represent calcified cells. All of this must be totally removed to prevent recurrence. In most cases, defects must be closed in two layers, to minimize “dead” space that might otherwise fill with blood.
One could argue that this child’s lesion should have been removed by a plastic surgeon—but the family had no insurance. Excision was therefore the treatment of choice; the most difficult aspect was persuading the patient to cooperate. (Sometimes, you have to wait years for the child to mature before you attempt it.) The outcome in this case proved to be quite acceptable. Of course, the lesion was sent to pathology, which confirmed the pre-op diagnosis.
The differential includes epidermal cysts (which are almost unknown in prepubertal children), and sweat gland cysts.
TAKE-HOME LEARNING POINTS
- Pilomatricomas are benign cysts that originate from hair matrix cells, usually appearing on the head, neck, face, and upper extremities of children.
- The cysts are typically firm and round and often display a faintly bluish tone (as seen in this case).
- As solitary lesions, they are of little or no significance; when seen in multiples, however, pilomatricomas suggest the possibility of Gardner syndrome or myotonic seizure.
- Excision is the best treatment, though these can be left alone long enough to allow the patient to mature sufficiently to cooperate with the surgical process.