Pigmented eccrine poroma on scalp simulating melanoma
Poroma écrino pigmentado no couro cabeludo simulando melanoma

INTRODUCTION

The eccrine poroma is a benign lesion, usually solitary, which presents as a sessile or pedicled nodule of skin color and most often affects the palm or plant of the foot. It derives from the intradermal component of the eccrine sudoriparous duct^1,2. Due to its rarity, the pigmented variant can easily be confused with melanoma, in addition to other tumor lesions. Thus, dermatoscopy is an important tool to aid in diagnosing, but only histology can define it. A clinical case of pigmented poroma on the scalp is reported, a location considered atypical, simulating malignant melanoma.

CASE REPORT

A 73-year-old male patient, phototype IV on the Fitzpatrick Scale, has a personal history of hypertension, diabetes, arrhythmia, chronic non-dialysis renal failure, gout, and previous coronary angioplasty with the placement of 4 stents and stroke 10 years ago. He informed the appearance of painless scalp injury, growing in the last 6 months, associated with sporadic bleeding and healing difficulty.

He sought care with a dermatologist, and some diagnostic hypotheses of tumor lesion subtypes were suggested, being the main melanoma nodular. On dermatological examination, the lesion presented as a blackened nodule with an erythematous center of firm consistency, measuring approximately 1.5 cm in diameter (Figure 1). The dermoscopic examination showed a circumscribed nodule with blackened edges and a center with a predominant vascular pattern in blood cells (Figure 2).

Figure 1 - Blackened nodule with erythematous center on the scalp.

Figure 1 - Blackened nodule with erythematous center on the scalp.

Figure 2 - Dermatoscopy evidencing circumscribed nodule with blackened edges and center with predominant vascular pattern in blood cells.

Figure 2 - Dermatoscopy evidencing circumscribed nodule with blackened edges and center with predominant vascular pattern in blood cells.

It was decided to perform exeresis with minimal margins. The material was referred for pathological study, whose report was partially pigmented eccrine poroma with surgical margins free of neoplasia. The clinical hypothesis of malignant melanoma was ruled out, and the patient is under outpatient follow-up, with no signs of recurrence to date.

DISCUSSION

Pinkus was the first to describe the eccrine Poroma in 1956². This benign neoplasm appears as a firm nodule, pediculated or not, being more common in the palmar or plantar region. It may grow in weeks or years and is more frequent between the fourth and sixth decades of life^3,4. It has no predilection for sex or race, except for the pigmented variant, which affects slightly more black people⁵.

The term poroma refers to rare cutaneous attached tumors, in which its structure presents cells similar to those of the acrosyringium. Clinical variants include poromatosis, linear and pigmented eccrine poroma⁶. Its pathophysiology is unknown, but it is related to trauma, radiation or scarring⁷.

Due to the rarity of this lesion, there are few studies and cases published in the literature. It can often be clinically confused with seborrheic keratosis, pyogenic granuloma, basal cell carcinoma, squamous cell carcinoma, angiofibroma, or melanoma. For these reasons, it is considered a “great simulator,” and other tools can be used as a diagnostic aid, such as dermatoscopy and confocal microscopy ^8,9, but there is no consensus on the findings.

Minagawa and Koga, in 20106, described 12 cases of pigmented eccrine poroma in which dermoscopy had some structural patterns, the most common being the vascular pattern, with polymorphic, arboriform and staple vessels. Since the eccrine poroma can simulate several benign and malignant tumors on the dermatoscopic aspects, the authors state that it is important to consider the possibility of pigmented eccrine poroma in cases of pigmented lesions that present non-melanocytic patterns in dermatoscopy.

The poroma’s main histopathological finding is a circumscribed and compact proliferation of cuboidal keratinocytes that present monomorphic nuclei and eosinophilic cytoplasm.

In this clinical case, after dermatological examination and dermoscopic evaluation, the main diagnostic hypothesis was malignant melanoma. The few clinical cases published with a dermatoscopic study presented a similar history and diagnostic doubt, and the diagnosis was clarified only after histopathological evaluation^8,10.

The choice of treatment, in this case, was surgical excision, considered the gold standard. However, there are other therapeutic options as an alternative, including shaving or electrocautery. Because it is a benign lesion, the eccrine poroma has a good prognosis, with a very low recurrence rate.

CONCLUSION

It is concluded that it is important that the evaluation of pigmented skin lesions is done both clinically and with dermatoscopy, used as a tool that corroborates the diagnosis. Although eccrine poroma is a rare tumor, it should be considered a diagnostic hypothesis in cases where pigmented lesions do not have melanocytic characteristics, and the diagnosis is confirmed only after histopathological evaluation.