Malignant Eccrine Poroma of the Vulva: An Intriguing Case of a Rare Tumor at an Unusual Site.

Malignant eccrine poroma is a rare malignancy of the eccrine sweat glands, occurring most frequently on the lower extremities. It affects both sexes equally usually in the 6(th) to 7(th) decade of life. Metastasis to regional lymph nodes may occur in 20% that may be fatal in 60% cases. Its aggressive nature, rarity of occurrence, and unusual presentations make it very important to be evaluated properly by the clinician. We hereby report a case of a 75-year-old female presenting with two exophytic tumors over her vulva with local extension. On histopathological examination, it was diagnosed as malignant eccrine poroma. On magnetic resonance imaging of the pelvic region, metastatic extension in regional lymph nodes was found. She was treated by radical vulvectomy with bilateral inguinal and femoral lymph node dissection followed by radiotherapy.

What was known?

Eccrine porocarcinoma is a very rare sweat gland tumor that commonly occurs on the lower limb and trunk.

Introduction

Malignant eccrine poroma, also known as eccrine porocarcinoma (EPC), is a tumor arising from the epidermal portion of eccrine sweat gland. This tumor may occur de novo or develop from a preexisting lesion as degenerative progression, and it can manifest clinically as a solitary lesion with ulceration or as a plaque, polypoid, or verrucous lesion.[1] It mostly affects the elderly, and most frequent site of involvement is lower limb followed by trunk then head and neck. We report this case as malignant eccrine poroma presenting over the vulva is extremely rare and may cause diagnostic confusion.

Case Report

A 75-year-old female presented with two erythematous plaques over the vulval region of the left side. The lesions started 2 years back as small papules and enlarged gradually with relatively rapid growth for the past 6 months. Lesions had become repeatedly infected and would bleed on minor trauma. No other systemic complaint was present. On examination, there were two ulcerated erythematous swellings on the left labia majora [Figure 1a].

Figure 1

(a) Two erythematous lesions on labia majora. (b) A large ulcerated lesion covered with yellowish necrotic material. (c) Enlarged inguinal lymph node of the right side

The larger one measured 3 cm × 3 cm and was covered with yellowish necrotic material [Figure 1b]. The smaller swelling was about 2 cm × 2 cm in size. Lesions were firm and indurated on palpation. We also found multiple enlarged, nontender, inguinal lymph nodes [Figure 1c].

Routine hematological investigations were within normal limits except for mild anemia. Histopathology from the larger vulval lesion showed dermal tumor comprising broad anastomosing bands and trabeculae of cells having large hyperchromatic as well as vesicular irregularly shaped nuclei. Brisk mitotic activity and necrosis was also noted.

Overlying epidermis was atrophic and separated from the tumor [Figure 2a and b]. The patient was nonreactive for HIV 1 and 2 and venereal disease research laboratory. Chest X-ray showed no abnormality. Mantoux test was negative. Magnetic resonance imaging of the pelvis revealed the neoplastic involvement of lower one-third of the anterior vaginal wall [Figure 3a] along with encasement of bilateral femoral veins by the inguinal mass [Figure 3b]. The patient was referred to the Gynecology Department where her radical vulvectomy with bilateral inguinal and femoral lymph node dissection was done, and she is now undergoing radiotherapy.

Figure 2

(a) Photomicrograph showing a collection of nests of tumor cells in dermis separated by anastomosing bands (H and E, ×100). (b) Photomicrograph showing collection of clear and vesicular cells with some areas of necrosis (H and E, ×400)

Figure 3

Magnetic resonance imaging of the pelvis showing (a) heterogeneously enhancing hyperintense mass lesion in the lower third of vagina in sagittal section. (b) Bilateral enlarged inguinal lymph nodes encasing femoral veins in axial section

Discussion

EPC is a rare malignancy of sweat glands accounting for only 0.005% of all the epithelial cutaneous neoplasms. Pinkus and Mehregan reported the first case in 1963 and called it as “epidermotropic eccrine carcinoma,”[2] Later, in 1969, Mishima and Morioka introduced the term “eccrine porocarcinoma.”[3] Most common site of involvement is lower limb accounting for 50% of cases.[45] Scalp lesions occur in <5% cases. Other affected sites are face, ear, eyelids, abdomen, vulva, penis, and pubis.

No sexual predilection is seen, however prevalence varies in both sexes in diverse studies.[6] Theoretically, EPC progresses from benign to malignant. This is supported clinically by long history, mean duration of 8.5 years, and recent onset of rapid growth in longstanding cases. Histological reports of dysplasia and malignant change in benign variants including eccrine poroma and hidroacanthoma simplex support this theory.[7]

However, in this case, a 75-year-old female presented with de novo development of two malignant eccrine poroma lesions over the vulva with metastasis to regional lymph nodes and other local structures. Mortality rate in patients with lymph node metastases is 67%.[8] Distant metastasis although very rare has been reported.[9] The pathogenesis and roles of possible preinvasive precursors of this lesion are still unidentified.

Recently, role of p53 gene involved in tumor suppression has been implicated in EPC carcinogenesis.[10] Treatment of choice for EPC is total surgical excision with broad tumor margins and regional lymph node dissection if involved. There are still insufficient data on cryosurgery and electrosurgery to accurately assess indication and tumor recurrence. Chemotherapy with methotrexate, cisplatin, adriamycin, and bleomycin or isotretinoin and interferon alpha has been used with partial or little response.

Radiation therapy and chemotherapy seem to be ineffective to control tumor recurrence or metastasis.[5] EPC must be considered in the differential diagnosis of patients older than 50 years with longstanding tumors in the limbs and head – including basal cell carcinoma, Paget's disease, melanoma, and metastatic cancer. Biopsy is indicated and, even with a previous diagnosis of benign eccrine poroma, one must be attentive to risk of malignancy in the future or if it is a recurrence.

Conclusion

Malignant eccrine poroma is a very rare malignancy of sweat gland origin. Its occurrence over the vulval region is extremely unusual and hence diagnosis requires a very high index of suspicion. It may metastasize to regional lymph nodes and adjoining structures making early diagnosis and treatment very important for these cases. If treated in the early stage, surgery can be curative. Due to the limited availability of literature and cases documented, it is important to have a basic knowledge of this disease process as a differential diagnosis when dealing with cutaneous lesions of the vulva.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

What is new?

Malignant eccrine poroma lesions on the vulva with metastasis to bilateral inguinal lymph nodes are very rare and carry a sinister prognosis.