Dermatology Online Journal

Poroma of the hip and buttock
Deba P Sarma MD¹, Sadiq U Zaman MD¹, Eric E Santos MD², James M Shehan MD³
Dermatology Online Journal 15 (5): 10

1. Department of Pathology, Creighton University Medical Center, Omaha, Nebraska
2, St. Margaret's Hospital, Spring Valley, Illinois
3. Department of Medicine, Division of Dermatology, Creighton University Medical Center, Omaha, Nebraska. jimshehan@creighton.edu

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Abstract

Poroma is a benign adnexal skin tumor seen in middle aged individuals with no sex predilection. The acral sites are the most commonly affected regions. Hip or buttock as a location of origin has rarely been reported. We report two cases of poroma, one located on the hip of a 75-year-old man and the other on the buttock of a 60-year-old man.

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Case reports

Figure 1	Figure 2

Figure 3

Case 1. A 75-year-old man presented with a 1 cm dome-shaped red papule on the right hip (Fig. 1). Microscopic examination (Fig. 2) revealed a typical poroma composed of dark epithelial downgrowths with multiple attachments to the epidermis. The epithelial downgrowths showed several interconnections. The neoplastic cells were monomorphic, dark, and cuboidal with moderate amounts of cytoplasm showing intercellular bridges. There was no peripheral palisading or retraction artifact as is commonly seen in basal cell carcinoma. Foci of ductal luminal differentiation characterized by small ductal spaces surrounded by small epithelial cells and covered by eosinophilic lining towards the lumen (Fig.3) were also present. There was no evidence of necrosis, increased typical or atypical mitotic figures, or stromal invasion.

Figure 4	Figure 5

Case 2. A 60-year-old man presented with a 0.5 cm nodule on the left buttock. Microscopic examination (Fig. 4) of the excised lesion revealed a typical poroma with several downward interconnected proliferations of monomorphic basaloid cells. There were foci of well-formed ductal structures (Fig. 5).

Discussion

Poroma is a benign cutaneous adnexal tumor of sweat gland duct origin that typically presents as either a solitary skin-colored to red papule or as a small nodule on the distal extremities including the palms, soles, and digits [1]. Rarely has the lesion been described in other locations such as head and neck, chest, or abdomen [2]. The tumor occurs in adults affecting both sexes equally. The painless lesion is usually described as a slightly raised, red to skin-colored nodule, rarely larger than 3 cm in size, with occasional bleeding secondary to trauma. Some pigmented poromas may resemble a melanocytic neoplasm. Poromas have also been reported to arise in a nevus sebaceous implicating apocrine origin [3]. Numerous poromas occurring in a widespread distribution called poromatosis, has rarely been reported.

These tumors are predominately of eccrine duct origin and are commonly referred to as eccrine poromas. However, some poromas occurring in locations other than palms and soles show foci of sebaceous and pilar differentiation suggesting origin from apocrine glands [3]. Histologically, poroma shows intraepidermal nests of small monotonous polygonal cells with low mitotic activity. The tumor cells generally demonstrate direct downward growth into the dermis as interconnected basaloid proliferations. The intraepidermal nests of basaloid cells are smaller than the adjacent keratinocytes and show intercellular bridges. There are foci of maturation towards ducts characterized by lumen formation surrounded by eosinophilic material over small epithelial cells. Simple excision is the mainstay of treatment.

We are reporting these two cases of poroma because our search of the literature did not uncover any cases of poroma occurring in the hip or buttock regions.

References

1. Patterson JW, Wick MR. Nonmelanocytic Tumors of the Skin. Fourth Series.Fascicle 4. Washington D: Armed Forces Institute of Pathology; 2006:139-143.

2. Ackerman AB, Abenoza P. Neoplasms with eccrine differentiation. Philadelphia: Lea and Febiger; 1990:113-185.

3. Harvel JD, Kershmann RL, LeBoit PE. Eccrine or apocrine poroma? Six poromas with divergent adnexal differentiation. Am J Dermatopathol. 1996:18(1):1-9. [PubMed]

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