Eccrine Porocarcinoma of Scalp: An Uncommon Tumor at an Unusual Site

Introduction

Eccrine porocarcinoma (EPC) is a very rare malignant sweat gland tumor and those arising in the scalp, are still rarer. Very few cases are reported in literature [1]. Malignant eccrine poroma was first described in 1963 by Pinkus and Mehregan using the term epidermotropic eccrine carcinoma. It is regarded as the rare malignant counterpart of eccrine poroma, a benign tumor of the intraepidermal eccrine sweat gland duct [2]. Porocarcinoma is commonly found in older age group and usually located in the lower extremities (more than 50%), rarely may occur on scalp, face, ear, upper extremities, trunk and abdomen [1, 3]. In the scalp, it is commonly seen in occipital region [4, 5]. The tumor presents as nodular, infiltrative, ulcerated or polypoid growth [6]. Surgical resection is the treatment of choice. There is 17% incidence of local recurrence and an 11% incidence of distant metastasis [3]. We report a case of EPC of scalp arising from a pigmented eccrine poroma in a 35 yr old.

Case Report

A 35 yr old male, presented with a growth over the scalp since 6 years with increase in size and ulceration since 1 month. There were no other complaints. Local examination showed a 5 cm × 4 cm ulceroproliferative, non tender mass with blackish pigmentation in the right frontoparietal region (Fig. 1). Serous discharge was oozing out from the ulcerated nodule. His general and systemic examination was within normal limits. Clinical diagnosis of melanoma or pigmented squamous cell carcinoma was made. On investigation complete hemogram, biochemical parameters, and skull x-ray were all within normal limits. Wedge biopsy of the lesion showed ulcerated epidermis with atypical poroid cells extending into the dermis as anastomosing bands and dermal tumor islands (Fig. 2a). Eccrine differentiation was seen indicated by spiraling ductular structures (Fig. 2b). Areas of pigmented eccrine poroma were seen (Fig. 2c). Some of the cells had pleomorphic hyperchromatic nucleus with nucleolus and moderate cytoplasm. Focal mitosis, squamous differentiation and necrosis were also seen (Fig. 3a and b). A cluster of immature cells was also seen differentiating into adjacent adnexal structures (Fig. 3c). Histopathological diagnosis of eccrine porocarcinoma with areas of pigmented eccrine poroma was made. Clinically and radiologically there was no evidence of any lymph node or distant metastasis. Wide excision of the lesion with primary closure was done. Histopathology of the resected specimen showed eccrine porocarcinoma with tumour free resected margins. Patient is on follow up since 15 months with no evidence of locoregional recurrence.

Fig. 1.

Clinical picture showing ulcerated, blackish nodular mass in the right frontoparietal region of scalp measuring 5 cm × 4 cm

Fig. 2.

a: Ulcerated epidermis with atypical poroid cells extending into the dermis as anastomosing bands. H&E , 10×. b: Eccrine differentiation showing spiraling ductular structures. H&E, 10×. c: Areas of pigmented eccrine poroma. H&E, 10×

Fig. 3.

a: Areas of squamous differentiation. H&E, 40×. b: Necrosis. H&E, 40×. c: A cluster of immature cells differentiating towards adnexal structures. H&E, 10×

Discussion

Eccrine porocarcinoma is a rare tumour mainly occurring in elderly males. Lower extremities are the commonest sites involved. It is rarely seen in the scalp. Matloub reported a case of ulcerative porocarcinoma of occipital region involving pericranium [4]. Ritter et al. have reported one case of eccrine porocarcinoma in occipital region with intracranial extension [5]. However only one case of frontoparietal porocarcinoma has been reported [1]. Our patient had frontoparietal porocarcinoma which is free from underlying bone and pericranium. The tumor presents as nodular, infiltrative, ulcerated or polypoid growth and hence the clinical differential diagnosis include seborrheic keratosis, pyogenic granuloma, melanoma, squamous cell carcinoma, basal cell carcinoma, verruca vulgaris and metastasis [6]. Although the etiology remains unknown, it has been suggested that EPC arises from malignant transformation of eccrine poroma [3]. A long period of clinical history is often encountered [6]. Immunocompromised states such as HIV, Diabetes and organ transplantation are associated with increased risk of eccrine porocarcinoma [3]. Our patient had a preexisting eccrine poroma with a long clinical history, not associated with immunocompromised state.

Because of the rarity, it is challenging to diagnose based on clinical presentation alone, hence histopathological examination is always required [3]. Microscopy of the tumor will show tumor cells in cords and lobules of polygonal cells. The cells show nuclear atypia, with frequent mitosis and necrosis. Eccrine differentiation is indicated by spiraling ductular structures lined by cuticular material, zones of cytoplasmic glycogenation, intraepidermal discreet aggregates often centred around acrosyringeal pores. Melanin may be present in tumors of individuals from various racial background [7]. Our patient had a pigmented eccrine poroma with areas of malignant transformation into porocarcinoma. Immunohistochemistry is not strictly necessary in all cases and can be used to confirm the diagnosis [6]. Positive staining for carcinoembryonic antigen and angiotensin type 1 receptor with negative staining for S-100 protein can aid in making the diagnosis [3, 6].

Wide local excision and Mohs surgery are widely accepted treatment modalities for EPC [1]. Multinodularity, ulceration and rapid growth generally associated with local recurrence or distant metastasis [6]. If regional lymph nodes are involved, lymph node clearance should be done. Metastatic lesions can be treated with chemotherapy [1]. A complete response can be obtained with melphalan and intra-arterial infusions of 5-fluorouracil [8]. Some local benefit has resulted from peri-lesional injection of interferon -alpha and interleukin −2 [9]. Plunkett et al. obtained remission lasting for several months with Docetaxel [10]. Our patient had the disease limited to the scalp without lymphnode or distant metastasis. The lesion was ulceroproliferative type, the base of the lesion is smaller than the greatest dimension. He underwent wide excision of the lesion with primary closure and is doing well since 15 months with no evidence of recurrence.

Eccrine porocarcinoma is a rare tumour and those affecting scalp are still rare. Hence histopathological confirmation of the disease should precede definite surgical management. There is only less than 10 cases of scalp porocarcinoma in literature and to the best of our knowledge there has only been one previously reported case of frontoparietal porocarcinoma similar to ours.