Multiple skin-colored facial papules in a child.

An otherwise-well 9-year-old White male with a family history of acne presented with a 2-year history of firm dermal papulonodules on the anterior and lateral cheeks with no inflammation and no overlying epidermal change apart from scattered, coincidental ephelides (Fig 1). The forehead, back, and chest were spared. The patient had no fever, weight loss, night sweats, and lymphadenopathy. A topical antibiotic, antifungal, and retinoid were trialed without effect. Laboratory tests were unremarkable. A 4-mm punch biopsy was performed, and representative sections are shown (Fig 2, A-C).

Fig 1

Fig 2

Question 1: What is the most likely diagnosis?

Self-healing cutaneous mucinosis

Fibrofolliculoma

Syringomas

Follicular mucinosis

Angiofibromas

Answer:

Self-healing cutaneous mucinosis—Incorrect. Acute eruption of multiple papules, sometimes coalescing into linear infiltrated plaques on the head and neck, abdomen, and thighs. Often accompanied by systemic symptoms like fever, arthralgias, and myalgias. Spontaneous resolution over a period of 1-8 months is characteristic. Histologically, papular lesions show dermal mucin deposition.

Fibrofolliculoma—Incorrect. Presents as multiple small, skin-colored to hypopigmented papules involving the head, neck, and upper trunk. Histopathology displays slender strands of follicular mantle cells that emanate from a folliculosebaceous unit at the level of the isthmus. Occasionally, the stromal component of fibrofolliculomas can be rich in mucin, but this is distinct from the intraepithelial distribution of mucin in follicular mucinosis. In the setting of a fibrofolliculoma, strong consideration should be given to the possibility of Birt-Hogg-Dubé syndrome.

Syringomas—Incorrect. Clinically manifests as multiple small, firm, skin-toned papules at any site of the body but are prone to occur in the periorbital area, especially the eyelids. Histopathology demonstrates a proliferation of epithelioid cells with pale or pinkish cytoplasm forming nests and tubules of relatively uniform size.

Follicular mucinosis (FM)—Correct. Histopathology shows abundant, focally coalescent mucin within the follicular epithelium along with a surrounding perivascular and interstitial mixed inflammatory infiltrate composed of lymphomononuclear cells and abundant eosinophils.

Angiofibromas—Incorrect. Usually appear as a small skin-toned to red papule. If multiple, should consider an underlying disorder such as tuberous sclerosis, particularly if they present in childhood on the bilateral cheeks, nasolabial folds, nose, and chin. Histopathology consists of a dermal proliferation of plump or stellate fibroblasts in a collagenous stroma with an increase in the number of thin-walled, dilated blood vessels.

Question 2: Which histopathologic stain would detect the mucin deposition present in follicular mucinosis ( Fig 2 ,

Masson trichrome

Alcian blue (pH = 2.5)

PAS-D

Giemsa

Prussian blue

Answer:

Masson trichrome—Incorrect. Stains collagen blue-green and smooth muscle red.

Alcian blue (pH = 2.5)—Correct. Stains acid mucopolysaccharides blue.

PAS-D—Incorrect. Stains neutral mucopolysaccharides red.

Giemsa—Incorrect. Has many uses, including highlighting myeloid and mast cell granules purplish-blue.

Prussian blue—Incorrect. Stains ferric ions to form a deep blue color. Useful to distinguish hemosiderin from melanin.

Question 3: Which cutaneous neoplasm has been most commonly associated with FM?

Squamous cell carcinoma

Tricholemmal carcinoma

Mycosis fungoides (MF)

Basal cell carcinoma

Primary cutaneous follicle center lymphoma

Answer:

Squamous cell carcinoma—Incorrect. Can be rarely associated with histologic deposition of mucin, termed secondary mucinosis. Not associated with FM.

Tricholemmal carcinoma—Incorrect. Rare malignant counterpart of trichilemmoma with no associated FM. Histopathology shows infiltrative aggregations of pale keratinocytes with outer root sheath differentiation, cytologic atypia, and brisk mitotic activity.

MF—Correct. Two main clinicopathologic variants of FM have been proposed: a primary benign idiopathic form that occurs mostly in children and young adults, with a tendency to resolve spontaneously within 2 months to 2 years, and a secondary form occurring in older patients and associated with cutaneous lymphoma, mainly MF and Sézary syndrome. Incel Uysal et al and references therein demonstrate the rare occurrence of MF in children with FM. The differentiation between primary FM and MF-associated FM is difficult, and there is no single reliable distinguishing criterion. Detection of clonal T-cell gene rearrangements can be seen in both settings. Ultimately the clinical evolution of the disease is most informative.

Basal cell carcinoma—Incorrect. Secondary mucinosis commonly observed but does not involve hair follicles.

Primary cutaneous follicle center lymphoma—Incorrect. FM has occurred concomitantly with primary cutaneous follicle center lymphoma in only 1 case report of a man in his 60s. Geller et al and references therein note other non-cutaneous T-cell lymphomas, many not primary to the skin, that may have FM as an associated feature, but their co-occurrence is rarer than FM with MF.

Conflict of interest

None disclosed.