Case Reports

Primary Cutaneous Apocrine Carcinoma Arising Within a Nevus Sebaceus

Author and Disclosure Information

Nevus sebaceus (NS)(organoid nevus) is a benign follicular neoplasm that commonly occurs on the scalp, face, or neck. With time, it may give rise to benign or malignant tumors such as trichoblastoma, syringocystadenoma papilliferum, and basal cell carcinoma (BCC). Rarely, other types of neoplasms may develop. We present a 76-year-old woman with several trichoblastomas as well as a primary cutaneous apocrine carcinoma arising within a preexisting NS that was treated with frozen section excision.

Practice Points

  • Nevus sebaceus (NS) in the centrofacial region has been correlated with a higher risk for neurological abnormalities, including intellectual disability and seizures.
  • Historically, basal cell carcinomas (BCCs) were considered a common occurrence arising from an NS, prompting prophylactic surgical excision of such lesions.
  • More recently, it has been recognized that the most common tumor to arise from NS is trichoblastoma rather than BCC; in fact, BCC and other malignancies have been found to be relatively rare compared to their benign counterparts.
  • In light of this discovery, observation of NS may be a more prudent course of treatment versus prophylactic surgical excision.


 

References

Nevus sebaceus (NS) is a benign hair follicle neoplasm present in approximately 1.3% of the population, typically involving the scalp, neck, or face.1 These lesions usually are present at birth or identified soon after, during the first year. They present as a yellowish hairless patch or plaque but can develop a more papillomatous appearance, especially after puberty. Historically, the concern with NS was its tendency to transform into basal cell carcinoma (BCC), which prompted surgical excision of the lesion during childhood. This theory has been discounted more recently, as further research has suggested that what was once thought to be BCC may have been confused with the similarly appearing trichoblastoma; however, malignant transformation of NS does still occur, with BCC still being the most common.2 We present the case of a long-standing NS with rare transformation to apocrine carcinoma.

Case Report

A 76-year-old woman presented with several new lesions within a previously diagnosed NS. She reported having the large plaque for as long as she could recall but reported that several new growths developed within the plaque over the last 2 months, slowly increasing in size. She reported a prior biopsy within the growth several years prior, which she described as an irritated seborrheic keratosis.

Physical examination demonstrated 4 distinct lesions within the flesh-colored, verrucous plaque located on the left side of the temporal scalp (Figure 1). The first lesion was a 2.5-cm pearly, pink, exophytic tumor (labeled as A in Figure 1). The next 2 lesions were brown, pedunculated, verrucous papules (labeled as B and C in Figure 1). The last lesion was a purple papule (labeled as D in Figure 1). Four shave biopsies were performed for histologic analysis of the lesions. Lesions B, C, and D were consistent with trichoblastomas, as pathology showed basaloid epithelial tumors that displayed primitive follicular structures, areas of stromal induction, and some pigmentation. Lesion A, originally thought to be suspicious for a BCC, was determined to be a primary cutaneous apocrine adenocarcinoma upon pathologic review. The pathology showed a dermal tumor displaying solid and tubular areas with decapitation secretion. Nuclear pleomorphism and mitoses were present (Figure 2), and staining for carcinoembryonic antigen was positive (Figure 3). Immunoreactivity with epithelial membrane antigen and cytokeratin 7 was noted as well as focal positivity for mammaglobin. Primary apocrine carcinoma was favored over metastatic carcinoma due to the location of the lesion within an NS along with a negative history of internal malignancy. Dermatopathology recommended complete removal of all lesions within the NS.

Figure1

Figure 1. Verrucous plaque and 4 distinct neoplasms (labeled A–D) on the left side of the temporal scalp.

Figure2

Figure 2. Apocrine carcinoma histopathology demonstrating solid and tubular areas with decapitation secretion (A)(H&E). On high power, marked nuclear pleomorphism and increased mitotic activity were observed (B)(H&E).

Figure3

Figure 3. Apocrine carcinoma demonstrating carcinoembryonic antigen staining positivity.

Upon discussing biopsy results and recommendations with our patient, she agreed to undergo excision with intraoperative pathology by a plastic surgeon within our practice to ensure clear margins. The surgical defect following excision was sizeable and closed utilizing a rhomboid flap, full-thickness skin graft, and a split-thickness skin graft. At surgical follow-up, she was doing well and there have been no signs of local recurrence for 10 months since excision.

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