Ann Dermatol.  2015 Oct;27(5):601-604. 10.5021/ad.2015.27.5.601.

Composite Tumor Associating Trichoblastoma and Seborrheic Keratosis

• Loh SH
• Lew BL
• Sim WY

• KMID: 2171461
• DOI: http://doi.org/10.5021/ad.2015.27.5.601

Abstract

Seborrheic keratosis is a common benign epidermal tumor histologically composed of basaloid and squamous cells. It mainly occurs on the face, scalp, and trunk, and presents clinically as a well-circumscribed, brownish to black papule, nodule, or plaque. Trichoblastoma is a relatively rare benign, slow-growing tumor showing differentiation toward the primitive hair follicle. It clinically manifests as a solitary, skin to erythematous colored, well-circumscribed dermal nodule located predominantly on the head and neck with a predilection for the scalp. Histologically, a well-demarcated mass of follicular germinative cells that show various degrees of differentiation, arranged in lobules, sheets, and nests, is located in the dermis or subcutaneous fat layer. We report the case of a 28-year-old female patient with a solitary, 2.0x4.0-cm black plaque with a 0.7-cm skin-colored nodule on the scalp. Histologically, the entire black plaque had prominent hyperkeratosis, acanthosis, and papillomatosis with horn cysts. The central nodule showed well-circumscribed, various-sized dermal tumor lobules without a connection to the overlying epidermis. The lobular aggregation was composed of numerous basaloid epithelial nests and multiple primitive papillary structures with distinct peripheral palisading of nuclei. According to these findings, the scalp lesion was diagnosed as a composite tumor associating trichoblastoma and seborrheic keratosis.

Keyword

Composite tumor; Seborrheic keratosis; Trichoblastoma

MeSH Terms

Adult
Animals
Dermis
Epidermis
Female
Hair Follicle
Head
Horns
Humans
Keratosis, Seborrheic*
Neck
Papilloma
Scalp
Skin
Subcutaneous Fat

Figure

• 

  Fig. 1 A 2.0×4.0-cm dark pigmented, verrucous plaque on the scalp. Centrally, a distinct 0.7-cm skin-colored, hairless nodule was observed.

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  Fig. 2 (A) Scanning view of the excision specimen (H&E, scanning view). (B) Biopsy specimen showing well-circumscribed, various-sized dermal tumor lobules. Prominent hyperkeratosis, acanthosis, papillomatosis, and pseudohorn cysts were seen adjacent to the tumor nodule (H&E, ×20). (C) The lobular aggregation was composed of numerous basaloid epithelial nests and multiple primitive papillary structures with distinct peripheral palisading of nuclei (H&E, ×200). (D) Marked hyperkeratosis, acanthosis, papillomatosis, several horn cysts, and mild basal hyperpigmentation were detected in the epidermis (H&E, ×100).

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  Fig. 3 (A) The entire trichoblastoma tumor lobules were stained against cytokeratin 19 (CK19) monoclonal antibody, showing a mild peripheral palisading of nuclei (×100). (B) Focal tumor cells showed weak CK17 expression (×100). (C) None of the tumor lobules showed immunolabeling against CD34 monoclonal antibody (×100).

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