Pilomatricoma at COVID-19 Vaccination Sites

Pilomatrixoma, pilomatricoma, or calcifying epithelioma of Malherbe, is a common benign tumor originating from hair follicles. It has been noted to develop at COVID-19 vaccination sites.

Case 1: Pilomatricoma Post-First COVID-19 Vaccination 

A 65-year-old man experienced a growing pilomatricoma on his left upper arm, coinciding with the site of his initial COVID-19 vaccine. The tumor, appearing three months after vaccination, was 3 cm in diameter, mobile, and infection-free. Surgical removal confirmed pilomatricoma, identified by basaloid cells and keratinization. No recurrence was noted three months following surgery.

Case 2: Subcutaneous Tumor Following COVID-19 Vaccination

In this instance, a 43-year-old Japanese woman developed a subcutaneous tumor at her COVID-19 vaccination site. The tumor, emerging immediately post-vaccination, grew over five months. Dermatological examination showed a distinct, multilocular tumor with redness, and ultrasound imaging revealed a hypoechoic mass. Surgical excision confirmed pilomatricoma, featuring anucleated and foreign-body giant cells. The patient remained symptom-free after her second vaccine dose.

Case 3: Bullous Pilomatricoma After COVID-19 Vaccination

A 30-year-old Chinese man presented with a lump on his left arm, which appeared following his COVID-19 vaccination and later developed a bullous form. Dermatological examination identified a well-defined pink nodule. Surgical removal revealed a "bullous pilomatricoma," with histopathology showing various cellular reactions. The patient had a smooth recovery post-surgery.

These cases emphasize a notable link between pilomatricoma and COVID-19 vaccination sites. Dermatologists should be aware of such occurrences, employing clinical examination, ultrasound imaging, and histopathological analysis for precise diagnosis and effective treatment. Increased awareness and diagnostic accuracy can reduce unnecessary procedures and enhance patient care.


Yang Z, Song F, Winters L, Zhong J. Development of Pilomatrixoma at the Vaccination Site: A Rare Complication of COVID-19 Vaccination - A Case Report. Am J Case Rep. 2023 Dec 6;24:e942280. doi: 10.12659/AJCR.942280. PMID: 38055654.

Nakazono M, Kawai M, Mizukami A, Kondoh A, Yamaoka H, Mabuchi T. Case of Pilomatricoma After Coronavirus Disease 2019 Vaccination. Tokai J Exp Clin Med. 2023 Apr 20;48(1):10-12. PMID: 36999388.

Zheng B, Wang S, Li C. Bullous pilomatricoma arising at a COVID-19 vaccination site. Dermatol Ther. 2022 Dec;35(12):e15962. doi: 10.1111/dth.15962. Epub 2022 Nov 1. PMID: 36318996; PMCID: PMC9878128.


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