Dermatology Online Journal

Pyogenic granuloma clinically and dermoscopically mimicking pigmented melanoma
Pedro Zaballos MD¹, Jesus Rodero MD¹, Patricia Serrano MD¹, Francisco Cuellar MD², Neus Guionnet MD³, Jose Maria Vives MD¹
Dermatology Online Journal 15 (10): 10

1. Dermatology Department. Hospital de Sant Pau i Santa Tecla. Tarragona. Spain. pzaballos@aedv.es
2. Melanoma Unit, Dermatology Department. Hospital Clinic, IDIBAPS. Barcelona. Spain
3. Pathology Department. Hospital de Sant Pau i Santa Tecla. Tarragona. Spain

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Abstract

Pyogenic granuloma is a common, benign, acquired, vascular growth of skin and mucous membranes that usually presents as a solitary, rapidly, growing, papule or polyp that bleeds easily after minor trauma. The clinical diagnosis of this lesion is usually straightforward. Moreover, the dermoscopic features associated with pyogenic granulomas have been described recently. However, occasionally this tumor can be difficult to differentiate clinically and dermoscopically from other pigmented and vascular lesions. We report the case of an 18-year-old male who presented with a round, purple-black nodule with hemorrhagic crust, 1 cm in diameter, located on the lower part of the thorax. Dermoscopic evaluation revealed the presence of a blue-white veil, a black blotch, polymorphous atypical vessels, milky-red areas, and hemorrhagic crusts. The subsequent histopathological examination revealed a pyogenic granuloma. We present a case of pyogenic granuloma clinically and dermoscopically indistinguisable from a pigmented malignant melanoma.

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Introduction

Pyogenic granuloma is a common, benign, acquired, vascular lesion of skin and mucous membranes, which usually presents as a solitary, rapidly growing, papule or polyp that bleeds easily after minor trauma. In most cases, patient history and clinical appearance provide adequate information in order to make a correct preoperative diagnosis. However, there are common benign and malignant tumors that may be clinically confused with pyogenic granuloma [1, 2]. Dermoscopy is a non-invasive tool, which has improved the diagnostic accuracy of pigmented and vascular lesions; the dermoscopic criteria of pyogenic granulomas have been recently published [3, 4]. However, dermoscopy does not assure 100 percent diagnostic accuracy and in some cases, pyogenic granuloma may be difficult to differentiate dermoscopically from other pigmented or vascular lesions [3, 4].

In this report, we describe a case of a pyogenic granuloma in which the clinical and dermoscopic features were indistinguishable from a malignant melanoma and therefore the diagnosis was more difficult.

Case report

Figure 1
Figure 1. Clinical findings. An 18-year-old male was referred to our clinic with a pigmented lesion on the thorax, present for 6 months. A round, purple-black, nodule with hemorrhagic crusts on the surface, 1 cm in diameter, located on the lower part of the thorax is observed.

An 18-year-old male was referred to our clinic with a pigmented lesion on the thoras, present for 6 months. He noted that the lesion was slowly getting larger and was bleeding easily. He denied a history of a pre-existing injury or pre-existing melanocytic nevus. His personal and family history was negative for melanoma. Clinical examination revealed a round, purple-black, nodule with hemorrhagic crusts on the surface, 1 cm in diameter, located on the lower part of the thorax (Fig. 1). Only a few clinically and dermoscopic benign nevi were additionally observed. The clinical differential diagnosis of the tumor was pyogenic granuloma, angiokeratoma or malignant melanoma. Dermoscopic evaluation of the lesion revealed the presence of a blue-white veil in the right part of the lesion, a black blotch in the upper part, polymorphous/atypical vessels in the left-upper part, milky-red areas mainly in the left portion, and finally some white structures and hemorrhagic crusts (Fig. 2). The tumor was excised; there was a strong suspicion of melanoma. The subsequent histopathological examination revealed a long, exophytic, eroded, pedunculated tumor composed of a proliferation of small blood vessels set in an edematous stroma. These features were consistent with a pyogenic granuloma (Fig. 3).

Figure 2	Figure 3
Figure 2. Dermoscopic findings. The figure shows the presence of a blue-white veil in the right part of the lesion (arrowhead), a black blotch in the upper part (asterisk), polymorphous/atypical vessels in the left-upper part (white square), milky-red areas mainly in the left portion (black square) and finally some white structures and hemorrhagic crusts. DermLite Foto (3Gen, LLC, Dana Point, CA, U.S.A.). (x10) Figure 3. The histopathologic examination revealed a long, exophytic, eroded, pedunculated tumor (A: hematoxylin-eosin, original magnification x 10) composed of a proliferation of small blood vessels set in an oedematous stroma (B: H&E, x40 and C: H&E, x100). These features were consistent with a pyogenic granuloma.

Discussion

The clinical diagnosis of pyogenic granulomas is usually straightforward. However, in some instances, the differentiation from other tumors is difficult. In 38 percent of one case series, the clinical diagnosis of pyogenic granuloma proved to be wrong [5]. Misdiagnoses documented in the clinical literature include benign tumors such as hemangiomas, inflamed seborrheic keratosis, common warts, melanocytic nevus, Spitz nevus, keratoacanthoma, and malignant tumors such as squamous cell carcinoma, basal cell carcinoma, metastatic carcinoma, kaposi sarcoma, and amelanotic melanoma.

Dermoscopy is a non-invasive, in vivo method, which has improved the diagnosis of pigmented and vascular lesions. Recently, Zaballos et al published the dermoscopic findings in a case series of 12 pyogenic granulomas [3]. They found a reddish homogeneous area in 92 percent of cases, a white collarette in 85 percent, "white rail lines" that intersect the lesion in 31 percent, and ulceration in 46 percent of pyogenic granulomas. The dermoscopic pattern composed of the presence of a reddish homogeneous area surrounded by a white collarette and the absence of specific criteria for melanocytic or nonmelanocytic tumors, was identified in 85 percent of pyogenic granulomas and considered characteristic of these tumors [3]. They did not observe bluish, brown, or black pigmentation in their pyogenic granulomas.

We observed in this pyogenic granuloma the following structures: a blue-white veil, one big blotch, polymorphous/atypical vessels, milky-red areas, white structures and hemorrhagic crusts. The blue-white veil is a dermoscopic structure composed of an irregular, confluent, bluish homogeneous area with an overlying white "ground-glass" haze that cannot occupy the entire lesion. In melanocytic lesions, the histopathologic correlation of the blue-white veil results from the presence of an acanthotic epidermis with compact orthokeratosis overlying large amounts of melanin in the dermis. Some authors have studied the diagnostic significance of this structure and found a strong association with melanoma [6, 7, 8, 9]. Menzies et al. found that this structure had a specificity of 97 percent for melanoma [7]. A blotch is a dark structureless area usually due to a large concentration of melanin pigment localized throughout the epidermis and/or dermis, which visually obscures the underlying structures [6]. The presence of irregular blotches, as in our case, ranked sixth of 24 diagnostic features in discriminatory power between melanoma and nonmelanoma in the Consensus Net Meeting On Dermoscopy with an Odds ratio of 4.1 [6]. It is important to note that the recognition of blotches had a low interobserver agreement in the above-mentioned virtual consensus meeting, with a k of 0.21; the upper big blotch could be considered as a dark lacuna, structure associated with solitary angiokeratomas [10] by some dermoscopists. However, in our opinion, this isolated structure has a more irregular form, a more heterogeneous color and poorer delimitation than lacunae. The histopathologic correlation of the blue-white veil and the blotch of our case may be attributed to the presence of a superimposition of numerous small capillaries and proliferating vessels, some of them partially thrombosed, that were set in an edematous stroma of this polypoid pyogenic granuloma.

Regarding vascular structures, we observed the presence of dotted and linear-irregular vessels that form the criterion "polymorphous/atypical vessels" and milky-red areas [11]. Argenziano et al published that the more common vascular patterns seen in melanomas were the linear-irregular typology (33.3%), dotted vessels (22.7%) and polymorphous/atypical vessels (20%) [11]. The last vascular structure, which we observed in our case, had a predictive positive value for melanoma of 52.6 percent [11]. On the other hand, milky-red areas, although rarely seen (4.7% of melanomas), showed the highest predictive value for melanoma (77.8%) in the same study [11]. The other two dermoscopic structures: white areas, due to a compact orthohyperkeratosis, and hemorrhagic crusts, because of the bleeding of the lesion, are unimportant findings for the diagnosis.

In conclusion, we report a case of polypoid pyogenic granuloma clinically and dermoscopically mimicking a melanoma; this illustrates that dermoscopy does not assure 100 percent diagnostic accuracy and therefore histopathologic examination should be performed in all cases of pyogenic granulomas.

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