Importance of Individual Ghost Cells in Fine-Needle Aspiration Cytology Diagnosis of Pilomatricoma

Abstract

Background: Although histological diagnosis of pilomatricoma is not difficult because of its unique histological features, cytological diagnosis through fine-needle aspiration cytology (FNAC) is often problematic due to misdiagnoses as malignancy.

Methods: We reviewed the cytological features of 14 cases of histologically-proven pilomatricoma from Korea Cancer Center Hospital, with a discussion on the diagnostic pitfalls of FNAC.

Results: Among 14 cases of pilomatricoma, 10 (71.4%) were correctly diagnosed through FNAC, and two (14.3%) were misdiagnosed as carcinoma. Cytologically, all cases had easily recognizable clusters of basaloid cells and foreign body-type multinucleated cells. Although ghost cells were also found in all cases, some were inconspicuous and hardly recognizable due to their small numbers.

Conclusions: An accurate diagnosis of pilomatricoma in FNAC is feasible with consideration of clinical information and close examination of ghost cells.

Keywords: Fine-needle aspiration cytology; Ghost cells; Pilomatricoma.

Fig. 1.

Cytological features of pilomatricoma. (A) Low power view exhibiting large clusters of basaloid cells, ghost cells (thick arrows), and a multinucleated giant cell (thin arrow) in an inflammatory background. (B) Large clusters of basaloid cells mimicking carcinoma. (C) Ghost cells. (D) Nucleated squamous cells. (E) Foreign body-type multinucleated giant cell (right upper), small cluster of basaloid cells (left upper), calcific debris (lower), isolated ghost cell (arrow), and inflammatory cells. (F) Cellular debris (Papanicolaou stain).

Fig. 2.

Variable features of ghost cells in aspirates of pilomatricoma. (A) Ghost cell sheet showing abundant cytoplasm with distinct cell borders and central unstained area. (B) Clusters of ghost cells with peripheral basaloid cells. (C) Isolated ghost cells (arrows) and a small cluster of nucleated squamous cells in an inflammatory background. (D) Predominance of basaloid cell clusters and a few ghost cells (arrows). (E) Ghost cell nests (arrow) at the periphery of a large cluster of basaloid cells. (F) A single ghost cell (arrow) can be overlooked due to a basaloid cell cluster.

Fig. 3.

Fine-needle aspiration cytology smear from pilomatricoma mimicking carcinoma. (A) Tight clusters of basaloid cells and necrotic debris (thin arrow) simulate carcinoma. However, a few scattered ghost cells are noted (thick arrows). (B) A nest of nucleated keratinizing squamous cells (center) may raise the suspicion of carcinoma. Nevertheless, if ghost cells are noted (arrows), a correct diagnosis of pilomatricoma can be made.