A 34-year-old man presented with a slowly growing, solitary, asymptomatic, skin-colored, exophytic nodule, 9×7 mm, rubbery-to-firm in consistency on the right ala of the nose of 5-years duration (Fig. 1a).
An 18-year-old woman presented with a solitary, asymptomatic, light brown, dome shaped, 5×8 mm, firm nodule with a central debris-filled punctum on the right side of the nose of 5-months duration (Fig. 1b).
Histopathological examination of both cases revealed a dome-shaped nodular skin lesion composed of multiple dilated infundibulocystic structures filled with keratin with only focal epidermal communications. Numerous sebaceous lobules were attached to the infundibular structures. The follicular structures were surrounded with fibrous sheaths and were separated from the adjacent stroma by cleft-like spaces (Fig. 2). The stroma appeared densely collagenous (black arrow, Fig. 2a) with spindle cells (dashed arrow, Fig. 2a), foci of adipocytes (diamond headed and black arrows, Fig 2a and b, respectively), and vascular spaces.
What is your diagnosis?
The histopathological findings are diagnostic of folliculosebaceous cystic hamartoma (FSCH).
FSCH is a rare hamartoma with follicular, sebaceous, and mesenchymal elements, which was initially described by Kimura et al. 1. It has higher frequency in eastern Asian countries 2. It usually affects the center of the face, mainly the nose; yet, extra facial sites have also been reported 2–5. It has no specific clinical features. Although it usually presents as a skin-colored papule or nodule, erythematous lesions and giant variants were also described 2,3. Patients typically present in young adulthood, but age distribution is wide, and congenital lesions have also been reported 5. It shows no sex predilection 2.
The most important histopathological differential diagnosis of FSCH is sebaceous trichofolliculoma. The rare communication with the surface epidermis and the evident variable mesenchymal components favor FSCH over sebaceous trichofolliculoma and points to its hamartomatous nature. The mesenchymal components, which include a collagenous stroma with spindle cells, collagen bundles, elastic fibers, adipose, and vascular tissue, generally constitute the integral parts of the tumor that may at times predominate 1,2.
Our patients showed typical histopathological features of FSCH. We believe that this hamartoma is under-reported and not as rare as appears in the literature.
1. Kimura T, Miyazawa H, Aoyagi T, Ackerman AB. Folliculosebaceous cystic hamartoma. A distinctive malformation of the skin. Am J Dermatopathol 1991; 13:213–220.
2. Ansai S, Kimura T, Kawana S. A clinicopathologic study of folliculosebaceous cystic hamartoma. Am J Dermatopathol 2010; 32:815–820.
3. Sturtz DE, Smith DJ, Calderon MS, Fullen DR. Giant folliculosebaceous cystic hamartoma of the upper extremity. J Cutan Pathol 2004; 31:287–290.
4. Bolognia JL, Longley BJ. Genital variant of folliculosebaceous cystic hamartoma. Dermatology 1998; 197:258–260.
5. El-Darouty MA, Marzouk SA, Abdel-Halim MR, El-Komy MH, Mashaly HM. Folliculo-sebaceous cystic hamartoma. Int J Dermatol 2001; 40:454–457.