Abstract

Seborrheic keratosis is a common benign epidermal tumor of the skin. Pigmented seborrheic keratosis is a relatively rare variant of the entity. Here it has been reported a rapidly growing cutaneous hairy hemorrhagic lesion exhibiting discoloration including pinkish, light and dark brownish, black areas with irregular border in an adult man. Following clinical examination and dermoscopic evaluation, histopathologic investigation was required for the accurate diagnosis. After the surgical excision of the lesion, it has been diagnosed as pigmented seborrheic keratosis upon microscopic evaluation of the specimen. This case report emphasized the importance of histopathologic evaluation for clinically uncertain and suspicious cases.

Keywords: dermoscopic examination; histopathologic evaluation; pigmented seborrheic keratosis.

Citation: Namik T. Pigmented seborrheic keratosis: The importance of histopathological evaluation distinguishing from melanoma. Open J Clin Med Images. 2021; 1(1): 1010.

Introduction

Seborrheic keratosis (SK) is a common acquired benign epidermal skin tumor and shows increasing incidence with age. Usually at age 60, it reaches peak point. It is mostly seen in forehead, neck, trunk and genital area [1,2]. It has different subtypes and variable morphology. Appearance of the lesion can be confused with basal cell carcinoma, melanoma, squamous cell carcinoma and other malignancies [3,4]. Dermoscopy is easy, quick and a noninvasive examination. However, inconclusive results may be obtained due to some unclear, complicated and subtle structures of the skin [5,6]. In such clinical situations, after the surgical excision, histopathologic evaluation may be required. In this case report, an adult man with pigmented seborrheic keratosis exhibiting discoloration (pinkish, light and dark brownish, black areas), hemorrhagic regions, comedo like structures, exophytic papillomatous features with irregular border of the lesion on dermoscopic inspection was introduced.

Case report

A 61-year-old-man complained a rapidly growing dark coloured mole on the right temporal region during the last three months. In his medical history he had no excessive sun exposure prior to onset of symtoms. The history of trauma was absent. He neither smoked nor drank in his life time. Values for complete blood cell count and coagulation tests were within normal limits. Dermatological physical examination required dermoscopic evaluation (Figure 1).

Figure 1: Clinical photograph of the right temple showing 30 X 20 X 6 mm hairy, discoloration including pinkish, light & dark brownish, black areas, hemorrhagic lesion with irregular border.

Papillomatous cutaneous lesion in front of the hairy scalp border on the right temporal area was demonstrated during the dermatological examination. Dimensions of lesion were 30 X 20 X 6 mm. Discoloration including pinkish, light and dark brownish, black areas, hemorrhagic regions, comedo-like openings, exophytic papillomatous structures with irregular border of the lesion were observed during dermoscopic inspection (Figure 2).

Figure 2: Dermoscopic features of the lesion.

Although the macroscopic view of the lesion on clinical examination and dermoscopic evaluation resembles a benign melanocytic lesion as papillamotous nevus; rapid growing nature, hemorrhagic regions, discoloration including pink, black, light and dark brown colours and irregular border of the papillomatous cutaneous lesion, have made the diagnosis of the lesion uncertain and suspicious.

Histopathologic evaluation was needed for the ultimate diagnosis. Surgical excision of the lesion was performed.

Histopathology showed papillomatosis, acanthosis, keratinocyte proliferation, cysts including keratin structures and increased pigmentary melanocytes in basal layer in hematoxylin and eosin stain X40, it was diagnosed as pigmented seborrheic keratosis upon microscopic examination of specimen.

Discussion

The etiopathology of SK is not clear. SK affects both sexes equally. Chronic exposure to ultraviolet radiation may be an important aetiological factor. There was no chronic exposure to the sun in our case. A research including 206 SK cases reported the mean age of biopsy-proven in men as 61,9 years. In the same article the incidence of SKs on the scalp was 20,9 %.7-9 The age of our case was 61,1 years and the location of the lesion was in front of the ear in the forehead-hairline boundary on the right temporal area of the hairy scalp.

SKs have a large clinical variability. Histopathological variants can be summarized as adenoid, clonal, acanthotic, hyperkeratotic, irritated, melanoacanthoma and verricous with keratoacanthoma-like features. All of the subtypes have acanthosis, hyperkeratosis and papillomatosis [7,8].

Histopathologic examination of our case showed; papillomatosis, acanthosis and keratinocyte proliferation hematoxylin and eosin stain X40 (H&E X40) (Figure 3); keratinocyte proliferation and cysts including keratin structures (H&E X100) (Figure 4); increased pigmentary melanocytes in basal layer (H&E X200) (Figure 5) and cysts including keratin structures (H&E X100) (Figure 6). Under the light of these findings, histopathologic diagnosis was pigmented seborrheic keratosis.

Figure 3: H&E X40; Microphotograph showing histopathologic features of PSK. Papillomatosis, acanthosis and keratinocyte proliferation were observed.

Figure 4: H&E x100; Microphotograph showing histopathologic features of PSK. Keratinocyte proliferation and cysts including keratin structure were observed.

Figure 5: H&E x200; Microphotograph showing histopathologic features of PSK. Increased pigmentary melanocytes in basal layer were observed.

Figure 6: H&E x100; Microphotograph showing histopathologic features of PSK. Cysts including keratin structure were observed.

An article reported that out of two hundred and six patients clinically diagnosed as SK during the dermoscopic examination, ninety-one cases were subsequently confirmed to be Ganoderma applanatum (Pers.) Pat. and Collybiaconfluens (Pers.: Fr.) misdiagnosed after the histopathologic evaluation of skin biopsy specimens. Furthermore, the incidences of basal carcinoma, squamous cell carcinoma and Bowen’s disease, early form of skin cancer were 4%, 3% and 2%, respectively [8].

Conclusion

In conclusion, dermoscopic evaluation may not be sufficient for the differential diagnosis of benign types and malignant characteristic features [3-5,10,11].

In the light of most recent literatures, our team suggests that total surgical resection or at least biopsy and afterwards histopathologic evaluation must be proposed to patients who have subtle lesions for SK to exclude premalignant and malignant diseases.

Declarations

Human subject: Informed consent was given by the patient in this case report.

Conflicts of interest: All authors declared no financial support received from any organization and no conflicts of interest. I do not believe that there is a conflict of interest that could potentially be construed to affect the material contained in the manuscript that is being submitted to the Journal.

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