Tumor of follicular infundibulum: An unsuspected cause of macular hypopigmentation

Abstract

We present three cases of a rare eruptive variant of tumor of follicular infundibulum. Two patients presented with hypopigmented macules. The clinical differential diagnoses considered in these two cases were vitiligo, lichen sclerosus et atrophicus, and idiopathic guttate hypomelanosis. In the third case, the lesions were hypopigmented flat topped maculo-papules diagnosed clinically as verruca plana. In all three cases, the histopathological features of plate like growth of pale keratinocytes connected to the epidermis and peritumoral condensation of elastic fibers were diagnostic. Although no satisfactory treatment is available, the exclusion of other clinical differential diagnosis particularly vitiligo with its psychosocial implications underscores the importance of skin biopsy.

Tumor of follicular infundibulum – reappraisal in a series of 28 patients with critical review of the literature

“…Similar to SK horn cysts and squamous eddies are seen in TFI. 3,20,22 In addition, both TFI and SK may show features of sebaceous differentiation, as previously reported, although this is a rare phenomenon in SK. 22,25,30 The term "acanthomatous superficial sebaceous hamartoma", also named "superficial epithelioma with sebaceous differentiation", 3,[30][31][32][33][34][35] describes cases which we would nowadays classify as seborrheic keratosis with sebaceous differentiation.…”

“…24 Multiple eruptive lesions of TFI, also called infundibulomas, 4,5 account for around 7% of cases. 12 They tend to affect the head/neck and trunk and then typically present as small, well defined hypopigmented papules or more frequently macules as shown in figures of several previous publications, [4][5][6][7][8][9][10][11][12][13][14][15][16][18][19][20][21] simulating seborrheic ker-atosis, type stucco keratosis. Clinical images from Kossard et al 4 are presented as an excellent representative example of such cases (Figure 9).…”

“…2 In the following years the histopathological features of TFI expanded and included cases with a desmoplastic growth pattern, the formation of horn cysts, squamous eddies, ductal as well as sebaceous differentiation and even germ like structures. 3,11,20,22 An isthmic differentiation was favored which is characterized by more pale, eosinophilic keratinocytes than infundibular ones, having abundant illdefined cytoplasm and occasionally sebaceous elements, accompanied by single cell necroses.…”

Eruptive Tumors of the Follicular Infundibulum: An Unexpected Diagnosis of Hypopigmented Macules

“…For the depressed lesions, differential diagnosis includes acne scars, atrophic lichen planus, lichen sclerosus et atrophicus, disseminated superficial actinic porokeratosis and discoid lupus erythematosus [ 3 , 6 ]. Finally, differential diagnosis of papular lesions includes basal cell carcinoma, melanocytic nevi, seborrheic keratosis, actinic keratosis, prurigo nodularis, warts and trichoblastoma [ 3 , 6 , 7 ]. Because of the variety of clinical presentations, the histopathological study is the most important method for providing a definite diagnosis.…”

Tumor des follikulären Infundibulums – Neubewertung in einer Serie von 28 Patienten mit kritischer Analyse der Literatur

“…Ähnlich zur SK werden Hornzysten und sogenannte squamous eddies auch beim TFI beobachtet. 3,20,22 Darüber hinaus können beide, TFI und SK, eine sebazäre Differenzierung aufweisen, wie zuvor beschrieben, wenngleich dies ein seltenes Phänomen bei seborrhoischen Keratosen darstellt. 22,25,30 Die Bezeichnung "akanthotisches superfizielles sebazäres Hamartom", auch genannt "superfizielles Epitheliom mit sebazärer Differenzierung", 3,[30][31][32][33][34][35] beschreibt Fälle, die wir heutzutage als seborrhoische Keratose mit sebazärer Differenzierung klassifizieren würden.…”