Sir,
A 19-year-old male patient presented to the dermatology outpatient clinic with a history of a swelling over his scalp of 7 years' duration. The lesion was asymptomatic except for mild tenderness. He had a history of pus-filled lesions at multiple sites on the scalp, including the current one, which later developed into hard lesions. He was intermittently treated with shampoos and antibiotics. The patient and his family had no history of any other significant skin or systemic disease.
On examination, a hard, nontender nodule was seen on the scalp, measuring approximately 2 cm × 2 cm in size with an adjacent smaller nodule of similar consistency [Figure 1]. Dermoscopy (Foto II Pro, ×10, polarized) showed central areas of whitish-yellow structure-less areas with peripheral whorled and cerebriform patterns [Figure 2]. The structure-less areas correspond to the areas of ossification. All the other laboratory investigations, including calcium and Vitamin D levels, were within the normal limits. A final diagnosis of osteoma cutis, probably secondary to a folliculitis, was made.
Figure 1.
Nodule over the scalp with a smaller adjacent nodule
Figure 2.
Dermoscopy (polarized ×10, Foto II Pro) showing central areas of whitish-yellow structure-less areas with peripheral whorled and cerebriform patterns
Excision biopsy from the lesion showed focal areas resembling eosinophilic bony tissue and showing osteoblastic rimming along with scattered osteocytes within distinct lacunae[Figures 3 and 4].
Figure 3.
Histopathology shows focal areas resembling eosinophilic bony tissue showing osteoblastic rimming along with scattered osteocytes within distinct lacunae (H and E, ×40)
Figure 4.
Histopathology shows focal areas resembling eosinophilic bony tissue showing osteoblastic rimming along with scattered osteocytes within distinct lacunae (H and E, ×200)
Osteoma cutis refers to the formation of normal bone tissue within the skin. Osteoma cutis can be primary, when it develops de novo, without any preexisting skin lesion or secondary, after any inflammation, injury, or tumor.[1,2,3] Ossification can occur in two ways mainly – either because of mesenchymal cells differentiating into osteoblasts or by osteoblastic metaplasia of mesenchymal cells like fibroblasts. Primary osteoma cutis can occur in different forms – multiple miliary osteoma, isolated osteoma, and congenital plaque-like osteoma cutis. Primary osteoma cutis can also be associated with syndromes such as Albright's hereditary osteodystrophy.[1] To the best of our knowledge, dermoscopy of osteoma cutis has not been well described in the available literature. The dermoscopic differential diagnosis would include other causes of dystrophic calcification, which can also show whitish structure-less areas. However, osteoma cutis can be easily differentiated on histopathological examination, which shows well-circumscribed nodule of mature lamellar bone with osteoblastic rimming, within the dermis.[4]
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The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
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REFERENCES
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