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Pigmented nodular hidradenoma masquerading as nodular malignant melanoma

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Pigmented nodular hidradenoma masquerading as nodular malignant melanoma
Raj Pal Singh Punia MD, Sukant Garg MD, Amanjit Bal MD, Harsh Mohan MD
Dermatology Online Journal 14 (1): 15

Department of Pathology, Government Medical College and Hospital, Chandigarh, INDIA.

Pigmentation in sweat gland tumors due to active melanocytes has been rarely reported [1, 2, 3] and is the basis of this report. The clinical appearance can be mistaken for melanoma.

Clinical synopsis

A 32 year old female noticed an asymptomatic, enlarging dark nodule on the medial aspect of her left arm 3 months before her initial visit. The results of her general physical examination were unremarkable. The lesion was a 3x2.5 cm ulcerated, pigmented, non-fluctuant, mildly tender, superficial nodule present on the skin. A clinical diagnosis of nodular malignant melanoma was made. The nodule was surgically excised and sent for histopathological examination.

Figure 1Figure 2
Figure 1. Encapsulated sharply demarcated nodule extending into subcutaneous tissue along with admixed dendritic melanocytes.(H&E, magnification X 400)
Figure 2. Photomicrograph showing black melanin pigment in melanocytes admixed with tumor cells (Masson-Fontana, ×400).

The epidermis was partially ulcerated and the dermis showed well-circumscribed, multilobulated, sheets of epithelial cells surrounded by dense bundles of collagen extending into subcutaneous tissue. Few tubular lumina lined by cuboidal to round tumor cells containing eosinophilic material, pigment granules and pigment laden macrophages were also present. The solid portion of tumor displayed polygonal to round tumor cells with eosinophilic cytoplasm and coarse nuclear chromatin. Numerous pigment-containing dendritic melanocytes were present among these epithelial cells (Fig. 1). Mason Fontana silver stain for melanin was positive (Fig. 2). Immunohistochemical stains S 100 and HMB 45 in the melanocytes were also positive. Based on above features, a diagnosis of pigmented nodular hidradenoma was made.


Nodular hidradenoma also called eccrine acrospiroma is a common benign adnexal neoplasm usually found on the scalp, face, or anterior trunk [4]. Enzyme histochemical studies and electron microscopic studies have confirmed eccrine sweat gland origin of this tumor; it can show differentiation along various parts of skin appendages. The presence of melanocytes in sweat gland tumors is extremely rare because normal sweat glands lack melanocytes and melanin pigment. Melanocytes, however, are present in sweat duct anlagen of the 14-week-old embryo [5]. Whether the persistence of these melanocytes in the sweat gland acrosyringium after fetal life and/or the possible secretion of melanocyte growth factor from the tumor cells are responsible for the tumor-incorporated melanocytes, remains to be determined.

Few lesions such as basal cell epithelioma, seborrheic keratosis, pseudoepitheliomatous hyperplasia, and even squamous cell carcinoma may show pigmentation from accompanying melanocytes [2]. The pigmented apocrine cystadenoma is dark in color owing to pigment other than melanin [1]. An occasional case report describes increased urinary excretion of 5-S-cysteinl dopa in a case of pigmented eccrine poroma of scalp [6]. In conclusion, our case is another rare example of pigmented eccrine neoplasm that should be kept in the differential diagnosis of pigmented skin lesions.


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3. Mousawi A, Kibbi AG. Pigmented Eccrine Poroma: A stimulant of nodular melanoma. Int J Dermatol. 1995; 34:857-8. PubMed

4. Lever’s Histopathology of the skin. 8th Ed;Philadelphia;Lippincott Raven,1997:747-803.

5. Hashimoto K, Gross BG, Lever WF. The ultrastructure of the human embryo skin.II. The formation of the intradermal portion of the eccrine sweat duct and of the secretory segment during the first half of the embryonic life. J Invest Dermatol. 1966; 46:513-29. PubMed

6. Jin KM, Nogita T, Toyoda H, Kawashima M, Hidano A. Pedunculated pigmented eccrine poroma of the scalp with increased urinary excretion of 5-S-csteinyldopa. J Dermatol. 1990; 17:555-8. PubMed

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