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Infundibulomatosis: A case report with immunohistochemical study and literature review

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Infundibulomatosis: A case report with immunohistochemical study and literature review
José Carlos Cardoso1, José Pedro Reis1, Paulo Figueiredo2, Óscar Tellechea1
Dermatology Online Journal 16 (1): 14

1. University Hospital of Coimbra, Dermatology Department, Coimbra, Portugal.
2. Portuguese Institute of Oncology, Pathology Department, Coimbra, Portugal


Tumor of the follicular infundibulum was first described in 1961 by Mehregan and Butler in a patient presenting with multiple papules. It is more frequent, however, as an isolated lesion affecting mainly the face, neck, and upper trunk. Clinical presentation is variable, requiring histology for the diagnosis, which reveals typically a plate-like proliferation of keratinocytes in continuity with the epidermis and hair follicles; some morphological features are reminiscent of the outer root sheath of the hair follicle. A well defined network of elastic fibers surrounding the tumor is usually present using the appropriate staining and this finding is specific because it is not found in other benign follicular tumors. Multiple infundibulomas are usually sporadic and there is no apparent association with internal malignancy. The authors report the case of a 30-year-old female patient with a 5-year history of multiple small discrete hypopigmented macules and papules, scattered over the submental and submaxillary regions and anterior neck. Histopathological findings were consistent with the diagnosis of tumor of the follicular infundibulum. Immunohistochemical study was performed to further characterize the proliferation.

Case report

Figure 1
Figure 1. Macular and slightly papular lesions over the chin, mandibular and anterior cervical region.

A 30-year-old female patient presented with multiple isolated round-shaped hypopigmented, slightly scaly macules and papules, 4-6 mm in diameter, scattered over the submental and submaxillary regions, as well as the anterior neck. The papules were asymptomatic and had been present for 5 years, with very slow progression.

Her past medical history was remarkable for asthma in childhood, drug allergies to penicillin and ketoconazole, and solar urticaria.

Initial diagnostic considerations were guttate hypomelanosis, pityriasis versicolor and inverse lentiginosis; additional entities considered in the differential diagnosis were acne scars and adnexal tumors, namely tricoepitheliomas, trichilemmomas, trichofolliculomas, and syringomas.

Figure 2Figure 3
Figure 2. Plate-like proliferation of pale keratinocytes in continuity with epidermis and follicular structures (Hematoxilin & Eosin, x100)

Figure 3. A network of elastic fibers focally present along the base of the proliferation. (Veroheff, x100)

Figure 4
Figure 4. Contrast between the absence of pigment in the tumor and the adjacent normal epidermis (Fontana-Masson, x200)

A biopsy from one of the lesions revealed a subepidermal plate-like proliferation in continuity with follicular structures, consisting of pale-staining monomorphous keratinocytes without cytologic atypia (Figure 2). These cells were positive for periodic acid-Schiff (PAS) staining; there was also PAS-positive material forming a thin hyaline membrane surrounding the base of the proliferation. Voerhoff staining revealed some areas in which elastic fibers were arranged in a network surrounding the base of the tumor (Figure 3). Fontana-Masson staining was negative, showing an obvious contrast with adjacent epidermis (Figure 4).

These findings were consistent with the diagnosis of multiple tumors of the follicular infundibulum (infundibulomatosis).

Further characterization was done by immunohistochemistry, revealing that the proliferation was positive for MNF-116 and cytokeratins (CK)5/6 and negative for Ber-EP4, Bcl-2, CD10, CK7, CK20, EMA, CEA and CD34; Ki-67 positivity was less than 5 percent, in keeping with a very low proliferation rate.

Treatment with 0.05 percent tretinoin cream proved ineffective.


The original report concerning the tumor of follicular infundibulum was published in 1961 by Mehregan and Buttler and described a patient with multiple lesions, as in our case [1]. Nevertheless, only a few cases of patients with multiple tumors were reported since then [2-8].

It is more often found as a solitary lesion, in which case it generally occurs in elderly patients, with a female predilection. The tumors affect mainly the face, neck, and upper trunk. Clinical appearance is usually nonspecific; it presents as a smooth or slightly keratotic papule and is often diagnosed as a seborrheic keratosis or basal cell carcinoma [3]. Only the distinctive histological features allow the diagnosis.

Cases of multiple tumors of the follicular infundibulum (infundibulomatosis) have seldom been described [1, 2, 3, 4, 5, 6]. They tend to occur in younger patients and present as macules, papules or depressed lesions, which may vary from skin-colored to erythemathous or hypopigmented. Lesions are preferentially distributed over the face, neck, and upper trunk, similarly to the solitary lesions. The tumor number ranges from fewer than 20 to more than one hundred (reported in 5 cases) [2, 4, 5, 6, 7]. Clinical considerations prior to making a definite diagnosis may vary according to the characteristics of the lesions: hypopigmented lesions may suggest the diagnosis of pityriasis versicolor, guttate hypomelanosis or even vitiligo; atrophic lesions may be confused with acne scars, focal dermal atrophy, and atrophic lichen planus; erythematous scaly lesions may resemble actinic keratoses, discoid lupus erythematosus, and actinic porokeratosis [1-7]. Other diagnostic considerations in the presence of multiple lesions of the face and/or neck are other adnexal tumors, namely tricoepitheliomas, trichilemmomas, trichofolliculomas, or syringomas.

Notwithstanding its possible variability, in a given patient lesions tend to be quite monomorphous and to have a quite characteristic distribution, except for those cases with more than 100 lesions in which they tend to be more widespread.

In the few cases described, there is no apparent family history of similar cases and these multiple tumors were not associated with internal malignancy. However, it is worth to stress that tumors of follicular infundibulum may be amongst other hamartomatous lesions in patients with Cowden syndrome [3, 9].

Histopathological findings are usually distinctive [1, 2, 3]. The tumor consists of a plate-like proliferation of pale-staining keratinocytes in continuity with the epidermis and follicular structures. Cells are monomorphous with no atypia; peripheral palisading of nuclei is a common feature [3, 4, 5]. Cytoplasm of tumor cells is PAS-positive because of the presence of glycogen. One of the most distinctive features is the presence of a network of elastic fibers surrounding the base of the tumor, which is not present in other benign follicular tumors [2, 4]. This finding was only focal in our case.

The cases reported as "multiple infundibular tumors of the head and neck" by G. H. Findlay show different characteristics and are probably a different entity [10]. In the later cases each lesion comprised clusters of enlarged follicular infundibula, somewhat similar to the findings observed in prurigo nodularis.

The immunohistochemical profile performed in our case showed positive staining for MNF 116 and CK5/6, but negative staining for Ber-EP4, Bcl-2, CD10, CK7 and CK20. We highlight the fact that Ber-EP4 and Bcl-2 were negative, which may be useful in the distinction of this tumor from superficial basal cell carcinoma in doubtful cases. Further studies are desirable to confirm if this immunohistochemical profile is consistent.

Treatment in the reported cases has ranged from topical keratolytics and topical corticosteroids (which result in minimal improvement) to long term etretinate (with incomplete clearing of lesions). Other options include curettage and excision, but these may lead to scarring that is as cosmetically disturbing as the original lesions. Good results with cryotherapy were reported in a limited number of cases [2].

Solitary as well as multiple tumors of the follicular infundibulum are benign proliferations. However, in one patient with over one hundred lesions, there was documented transformation of two tumors into basal cell carcinoma [6]. This fact, as well as its occurrence within the spectrum of lesions appearing in Cowden syndrome, probably make a follow-up of these patients advisable.


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