Morphological Spectrum of Pilar Cysts

BACKGROUND: Cysts of the skin are one of the commonly excised specimens in the surgical outpatient department. A majority of them being clinically diagnosed as sebaceous cysts, their true nature is only discernible on histopathological examination. Closer examination of the type of keratinization involved will throw light into the exact nature of the cyst. Trichilemmal or Pilar cyst is one such entity, which presents in both a non-neoplastic and neoplastic form. AIMS: The present retrospective observational study was undertaken to find out the incidence of these cysts in surgical pathology practice in a rural hospital and to enlist the various morphological forms that these cysts may take. MATERIALS AND METHODS: The histopathology files were reviewed for a period of 6 years for cases coded as pilar cyst. RESULTS: A total of eight cases (5.75%) were identified, which showed features of trichilemmal differentiation. A single case each of proliferating trichilemmal cyst and malignant proliferating trichilemmal tumors were noted. Most of the cases were seen among females on the scalp. CONCLUSIONS: Trichilemmal tumor is an uncommon histopathological entity. Many of these lesions may be mistakenly diagnosed due to lack of recognition of the unique type of keratinization.