A Case of Pencil-Core Granuloma after Hyaluronic Acid Filler Injection

Dear Editor:

A 62-year-old female presented with an asymptomatic subcutaneous nodule on the left cheek. She had received 4 sessions of hyaluronic acid (HA) filler injections in both nasolabial folds 4 years prior; a year later, the lesion had started to enlarge gradually. Physical examination revealed a well-defined 1.0 cm×0.5 cm-sized skin-colored to bluish subcutaneous nodule on the left nasolabial fold (Fig. 1A). We received the patient’s consent form about publishing all photographic materials. As a granulomatous reaction after HA filler injection was suspected, punch biopsy was performed. The biopsy contained a piece of hard foreign material resembling pencil lead, approximately 0.8-cm long (Fig. 1B). Histopathologic findings showed granulomatous inflammations with fibrosis, which was composed of histiocytes, foreign body giant cells, and dispersed black pigment throughout the dermis (Fig. 1C, D). The alcian blue stain for the detection of HA was negative. During a second interview with the patient, she recalled having a pencil-tip injury as an elementary school student. The patient was diagnosed with pencil-core granuloma and the residual tissue was excised. There has been no evidence of recurrences and complications for 2 years.

Fig. 1. (A) A well-defined 1.0 cm×0.5 cm-sized skin-colored to bluish subcutaneous nodule on the left nasolabial fold (arrow). (B) The pencil lead, which measured about 0.8 cm in length, with black pigmented subcutaneous tissues. (C) Granulomatous inflammation with dispersed black pigments and fibrosis in the dermis (H&E, ×10). (D) Granulomas composed of histiocytes, foreign body giant cells, and black pigments (H&E,×400).

Pencil-core granuloma (graphite granuloma) is a delayed foreign body reaction to retained fragments of pencil lead. Although pencil lead is generally known to be biologically inert for a long time, individual components such as graphite, clay, and various waxes could induce a tissue reaction¹. The mechanism for the formation of pencil-core granuloma remains unclear. However, it is thought that the dispersal of graphite particles, which is caused by repeated mechanical stimuli, results in an accumulation of macrophages; these accumulated macrophages release various cytokines and growth factors that induce tissue reactions². The time lag from pencil-tip injury to granuloma formation ranges from 1.5 to 58 years. This long lag period suggests that a long time is often required for the breakdown of graphite to a critical size, dispersal of particles to the interstitium, and granuloma formation¹,³.

To our knowledge, there are only three cases of pencil-core granuloma in the Korean literature (Table 1)⁴,⁵. In two previous cases, the lesion was located on the extremities, and the lag periods were shorter than in our case. We believe that less frequent mechanical stimulation on the face compared to that on extremities is the reason for delayed facial occurrence. Interestingly, in our case, the lesion presented after HA filler injections, which suggests that not only repeated injection procedures but also filler materials may trigger the graphite breakdown and accelerate the granuloma formation.

Table 1. Case reports of pencil-core granuloma in the Korean literature.

Case	Sex/age (yr)	Lesion site	Lag period (yr)	Size (cm)
Jeong et al.5	Female/39	Left heel	20	2×2
Kim et al.4	Female/19	Right hand	10	0.5×0.3
Our case	Female/62	Left nasolabial fold	50	1.0×0.5

In conclusion, physicians should be aware that pencil lead may cause delayed granulomatous reactions. All pencil-tip injuries should be assessed carefully and complete removal of remnant graphite from the wound is recommended.