Güncel Patoloji Dergisi 2019, Cilt 3, Sayı 1
Follicular (Infundibular or Infundibulocystic) Cutaneous Squamous Cell Carcinoma: An Under-Recognised, Rare Variant
1 Acıbadem Mehmet Ali Aydınlar Üniversitesi, Tıp Fakültesi, Patoloji Anabilim Dalı, İSTANBUL
2 İstanbul Eğitim ve Araştırma Hastanesi, Patoloji Bölümü, İSTANBUL
DOI : 10.5146/jcpath.2019.41 Aim: Many variants of cutaneous squamous cell carcinoma has been defined. Among them, follicular squamous cell carcinoma is an under-recognised, rare variant, which may result in confusion regarding its differentiation from other tumors. Histopathologic features of this entity and its differentitial diagnosis are the subject of this paper.

Case: A total number of 4 patients, 3 females and 1 male, with the ages of 44, 60, 67 and 82, presented with lesions varying in size from 0.5 to 2 cm at sun damaged areas of the face. The lesions were located at the edge of eye, right vestibule of the nose, zygomatic and preauricular regions. In the histologic examination, a vertically oriented tumor, arsing from hair follicle infundibulum, without any prominent connection with the epidermis, other than the follicular orifices, were detected. In the middle, there were infundibular canals, filled with keratin. The tumor cells displayed the cytologic feature of squamous cell carcinoma. In one of the cases infundibulocystic dilatation was prominent. In another case, the tumor arised from several hair follicles. In one case, keratinocytes with eosinophilic, pale cytoplasms, reminiscent of keratoacanthoma, were seen. However, there was no epidermal lipping with crater formation, a characteristic feature of keratoacanthomas. Accordingly, the diagnosis of follicular squamous cell carcinoma was established in all cases. In the differential diagnosis, keratoacanthoma, metastatic squamous cell carcinoma, tricholemmal carcinoma and inverted follicular keratosis were considered.

Conclusion: Follicular squamous cell carcinoma are malignant tumors, which developed in the upper part of hair follicle, the infundibular segment, with abrupt connections to the epidermis at follicular infundibula, without any sign of interfollicular epidermal connection. Recognition of follicular squamous cell carcinoma is essential in order to avoid misdiagnosis and to be able to differentiate keratocanthoma, metastatic squamous cell carcinoma and some tumors with hair follicle differentiation. Anahtar Kelimeler : Follicular, Infundibular, Infundibulocystic, Squamous cell carcinoma