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Fibroepithelioma of Pinkus induced by radiotherapy

  • Author(s): Holcomb, Maura J
  • Motaparthi, Kiran
  • Grekin, Sarah J
  • Rosen, Ted
  • et al.
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Fibroepithelioma of Pinkus induced by radiotherapy
Maura J Holcomb1 MD, Kiran Motaparthi1 MD, Sarah J Grekin2 MD, Ted Rosen1 MD
Dermatology Online Journal 18 (7): 5

1. Department of Dermatology
2. Department of Pathology
Baylor College of Medicine, Houston, Texas


Abstract

Fibroepithelioma of Pinkus (FEP) is a rare cutaneous neoplasm. Evidence supports classification as a variant of either basal cell carcinoma (BCC) or trichoblastoma. Reports of FEP arising in sites of preceding radiation therapy have been documented in the literature, but the relationship between radiotherapy and the development of FEP has not yet been defined. We report a case of FEP following radiation therapy for testicular cancer.



Case report


Figure 1Figure 2
Figure 1. Fibroepithelioma of Pinkus: sessile plaque located above the superior gluteal cleft

Figure 2. Fibroepithelioma of Pinkus: thin anastomosing strands of basaloid cells, low-power view

Figure 3
Figure 3. Fibroepithelioma of Pinkus: thin anastomosing strands of basaloid cells, high-power view

An 87-year-old man complained of a persistent sacral lesion, asymptomatic but present for approximately 20 years. Past medical history was significant for testicular cancer, treated with surgery and radiation therapy 35 years earlier. Physical exam revealed a sessile skin-colored plaque measuring 2.5 cm by 1.5 cm, located above the superior gluteal cleft (Figure 1). The clinical impression was suggestive of FEP. A punch biopsy was performed and histology revealed anastomosing basaloid trabeculae separated from the surrounding stroma by cleft formation (Figures 2 and 3), confirming the diagnosis of FEP. Interestingly, the patient actually sought medical attention owing to three clinically classic BCCs located about 2-3 centimeters away from the index lesion depicted; two of these BCCs were superior and one inferior to the index lesion and all were within the prior radiation field. The latter lesions were verified to be histologically typical BCCs by biopsy and treated by curettage and electrodessication.


Discussion

FEP was initially described in 1953 as premalignant fibroepithelial tumor of the skin and since this time FEP has been considered to be an unusual variant of BCC [1]. However, a more recent study suggested that FEP is actually a variant of trichoblastoma [2]. Evidence for classification of FEP as a trichoblastoma variant includes typically low levels of staining for P53 and MIB-1, markers, which are traditionally overexpressed in BCCs [2]. FEP also displays retention of merkel cells, a characteristic of benign neoplasms with follicular germinative differentiation but not of BCCs [2]. An increase in the number of epidermal merkel cells is also seen with chronic radiation dermatitis, which has been associated with the development of FEP [3]. However, a high percentage of both FEPs and BCCs express androgen receptors, which are rarely found in trichoblastomas [4].

FEP usually presents as a solitary gray-brown or skin-colored plaque; multiple lesions are occasionally seen [5]. FEP is most commonly found in the inguinal and lumbosacral areas in persons between 40 to 60 years of age [6]. FEP shows no predilection for sun-exposed sites, in contrast to BCC [2]. Histopathology demonstrates thin anastomosing strands of basaloid cells surrounded by an abundant stroma that forms an even border with the underlying dermis [2]. This patient’s lesional histology is thus prototypical for FEP.

The degree to which antecedent radiation contributes to the development of FEP is unclear. FEP has been documented to occur in areas of prior iatrogenic radiation in several studies. In one series, 9 of 20 FEPs were associated with preceding radiotherapy or repeated roentgenograms, typically several decades before the development of FEP [7]. Colomb in 1985 reported 14 patients with multiple BCCs and FEPs who had a history of previous radiotherapy or multiple fluoroscopic examinations [8]. FEP of the groin has been once previously reported in a patient who received radiation therapy for testicular cancer 14 years earlier [9]. These case reports and series strongly suggest an association between extensive exposure to ionizing radiation and FEP, an otherwise rare tumor. Radiotherapy has also been associated with the development of both trichoblastomas as well as BCCs [10]. In fact, many studies indicate that BCC is the most common type of skin cancer associated with previous radiation therapy [11].

Whereas aggressive behavior with local invasion or metastasis has not been reported, excision of FEP is recommended and is almost universally curative [2]. Topical imiquimod, although used effectively to treat superficial BCC, is ineffective in treating FEP [5]. As illustrated in the case reported herein, a high index of suspicion must be maintained with regards to the development of skin cancer, including the otherwise rare FEP, in patients with a history of localized radiation therapy. The clinical morphology of FEP might also reasonably suggest many benign processes, such as seborrheic keratoses, condyloma accuminata, keloids, and nevoid lesions. Thus, the history of previous radiation therapy might well suggest the correct diagnosis in the setting of equivocal clinical appearance.

References

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