1 Introduction

Tumours of cutaneous sweat glands are uncommon, with wide histological spectrum, complex classification and many different terms often used to describe the same tumour.¹ Skin contains two types of sweat glands (Fig. 1). Eccrine glands secrete an ultra filtrate of blood that cools the skin surface by evaporation.² These are small and true secretory glands distributed all over the body, secreting clear aqueous sweat. Apocrine glands are large and arise from follicular epithelium, secreting viscid milk-like droplets.³ In addition to these, two more sweat glands have been recently described: apoeccrine and mammary-like glands of the ano-genital area.¹ NA Obaidat et al. also propose the term ‘composite adnexal tumours of the skin’ which, in their opinion, would better reflect the common embryological origin of these lesions, and the potential variable combination of eccrine, apocrine, sebaceous and pilar differentiation. Although rare, unusual and among the less common group of swellings in the upper limb or hand, these tumours must be included in the differential diagnosis of benign as well as malignant lesions of the upper extremity.⁴Marenda and Otto estimated that highly malignant sweat gland carcinomas constitute 0.005 % of all skin tumours.⁵ We report seven cases of sweat gland tumours of the hand and six were benign and only one was malignant. Out of these seven tumours, two were eccrine poromas (EP), three were eccrine spiradenomas (ES), one eccrine acrospiroma (EA) – all benign. One patient had a malignant eccrine spiradenoma (MES).

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Fig. 1 Anatomy of Sweat gland.

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2 Case reports

Case no. 1: 38 year old man presented, with a dark, soft lump on the hypothenar area of his non-dominant left hand, with a history of blunt trauma to the area three years before presentation. Following this injury, he noticed a small, dark lump. On examination there was a soft, dark, umbilicated lump without any raw area and soddening of skin (Fig. 2). Clinical diagnosis was pyogenic granuloma. Surgical excision done under brachial block anaesthesia and tourniquet. Histopathology revealed a benign sweat gland tumour arising from epidermis and extending into dermis, the surface of the tumour was showing keratinization. Although there was no inflammatory reaction, haemorrhage, necrosis or cytological atypia, melanin pigment was present. This was reported as pigmented eccrine poroma. His post-op period was uneventful and there is no recurrence after 15 years (on telephonic comminuation).

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Fig. 2 Eccrine poroma of left palm.

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Case 2 : 25 year old female presented with a lump of four years duration, on her non-dominant left ring finger. There was no history of trauma. On examination, there was a firm lump on the ulnar side of the left ring finger; this was non-pulsatile, non-compressible, non-tender and free from the overlying skin. Tinel's sign was negative. Flexor tendons were not involved. Hyperaesthesia was noticed on the ulnar side, distal to this lump (Fig. 3). Clinical differential diagnosis was Giant cell tumor of tendon sheath (GCTTS) or Neurilemmoma. She was operated under ring block anaesthesia and a well-capsulated small tumour was excised. Neurovascular bundle was not involved. Histopathological diagnosis was eccrine poroma.

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Fig. 3 Eccrine poroma of left ring finger.

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Case no. 3: 40 year old man presented with a slowly enlarging, skin coloured, painless lump of two years duration on the pulp of his dominant right thumb. Past history, he had chemotherapy to cure his acute lymphocytic leukaemia. Clinical examination revealed a large, non-pulsatile, non-compressible, soft lump with a central hard core, within the pulp of his right thumb. The overlying skin was papery with atrophy of subcutaneous fat. Clinical diagnosis was fibroma (Fig. 4A). X-ray revealed a discrete soft tissue mass. Blood tests were unremarkable. He was operated under local anaesthesia and ring tourniquet. The incision was planned to allow complete excision of this mass as well as to maintain the shape of the thumb (Fig. 4 B). The mass was white, multi lobulated and had a capsule. The digital nerve or its branches were not encountered in the area of dissection. Histopathological diagnosis was nodular hidradenoma with patchy clear-cell pattern (eccrine acrospiroma). His recovery was uneventful and at the end of 15 years he has no recurrence.

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Fig. 4 (A) Eccrine acrospiroma- right thumb and excised Eccrine acrospiroma of right thumb (B).

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Case no. 4: A 74 year old female presented with a recurrent lump in her right dominant palm. Initially she had a small nodule excised in other hospital under local anaesthesia 25 years ago, with no histological examination. This recurred after four and half years following the original surgery; however, it was again excised under local anaesthesia. This time histopathology revealed low grade malignant adnexal tumor. Patient received radiotherapy. Recurrence was again noticed after 6 months. Fine needle aspiration biopsy was reported as malignant eccrine spiradenoma (Fig. 5), following which she was referred to our clinic. Blood tests and X-ray of the hand were normal, as were her chest X-ray and bone scan. Wide local excision was carried out, including part of the adherent palmar aponeurosis along with A-1 pulleys of the index and middle fingers and raw area was covered with a split thickness skin graft (STSG). Histopathology revealed a malignant adnexal tumour partly cystic, partly solid with features closest to malignant eccrine spiradenoma. Resection margins were confirmed to be negative. Six months later, the patient again had another recurrence, for which a wrist level amputation was done at another hospital. After this, she developed cervical and axillary lymph node metastasis and died after that.

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Fig. 5 Malignant recurrent eccrine spiradenoma – right palm.

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Case no. 5: A 22 year old male presented with a nodule on the ulnar side of his non-dominant left wrist since childhood. Recently he found it to be painful while doing gym. There was no history of trauma. It was not visible but palpable and it was extremely tender on touch. This was subcutaneous, free from deeper structures, non-pulsatile and with a negative Tinel's sign. Ultrasound revealed a soft tissue swelling. Clinical findings were suggestive of glomus tumour. He was operated under brachial block anaesthesia with tourniquet. The lump was well encapsulated and bi-lobed. It was easily and completely excised along with its capsule (Fig. 6). Histopathological diagnosis was eccrine spiradenoma. Immunohistochemistry confirmed presence of cytokeratin in the tumour cells. CD34 and SMA were negative. At the end of six months, patient was free of symptoms and without evidence of recurrence.

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Fig. 6 Eccrine spiradenoma – ulnar border of left wrist.

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Case 6: 55 year old female came with sever pain and swelling in left distal forearm since 7 years. She was treated conservatively but no relief so referred to us for further management. There was no history of trauma. It was not visible but palpable and it was extremely tender on touch. This was subcutaneous, free from deeper structures, non-pulsatile. Ultrasound revealed a small soft tissue swelling. Clinical findings were suggestive of glomus tumour. She was operated under brachial block anaesthesia with tourniquet. The lump was well encapsulated and multi-lobed. It was easily and completely excised along with its capsule (Fig. 7). Histopathological diagnosis was eccrine spiradenoma. At the end of eight months, patient was free of symptoms and without evidence of recurrence.

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Fig. 7 Eccrine spiradenoma – Multi lobulated tumour on dorso ulnar border of left wrist.

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Case 7: A 29 year old man presented with a small palpable but not visible nodule of 10 years duration, on the dorsal radial aspect of his left non-dominant wrist. There was no history of injury. He presented with a month's history of increase in size along with pain on pressure. Clinically there was a small, firm, non-pulsatile, non-compressible, subcutaneous tender nodule about 4 mm in diameter. Tinel's sign was negative. Clinical diagnosis was that of a glomus tumor. Excision under local anaesthesia with tourniquet revealed a yellow multi-lobulated mass. Histopathological report was eccrine spiradenoma. Follow up of 1 year did not show any recurrence.

3 Discussion

Skin tumours of sweat gland derivation were first described by Bilroth in the mid nineteenth century.⁶ Adnexal structures of the skin include hair follicles, sebaceous glands, apocrine and eccrine sweat glands.⁷ As there are no apocrine glands in the hand, only malignancies of eccrine type may arise in that location.² Eccrine glands are distributed throughout the human body except for in the glans penis, clitoris, labia minora and the inner surface of prepuce.⁸ Eccrine tumours arise from eccrine sweat glands and most frequently occur in the trunk and head. Since they are rare in the hand, details of their clinical features are only available from isolated case reports. Eccrine spiradenoma usually presents as solitary or multiple intra dermal nodules. The nodules are frequently extremely painful.⁹ In three of our patients they were extremely tender on touch, although not visible, mimicking glomus tumour. In 5th case, which was a bi-lobed tumour the diagnosis was facilitated only after immunohistochemical evaluation. Our case of malignant eccrine spiradenoma (MES) was a recurrent lesion and probably arose from an originally benign lesion which was excised 25 years ago in other hospital. In another reported case of MES of the thumb tip, the patient developed local recurrence with pulmonary metastases 10 years after excision; these were treated surgically. She was disease free at her last follow up two years later.¹⁰

Anthony C Zamboni et al. reviewed 12 well documented cases of MES, five were involving the hand. Despite the clinical presentation, a definitive diagnosis of all these 12 cases, as with our own case, was only achieved on histopathological examination. Malignant transformation of a benign appendageal tumour or hamartoma is a rare, but definite, phenomenon.¹¹ Based on the above observations; it is recommended that histological examination of any long standing cutaneous nodules of the hand to identify any potentially lethal MES and the benign ES that may undergo malignant transformation.¹⁰ We concur with this recommendation. Another literature review revealed 28 cases of MES out of which only one was involving the hand.⁵ It also showed that the clinical course of such tumours is characterised by local recurrences and eventual metastases, soon followed by death. MES never appears to arise de novo.¹² While the immunohistochemical profile of benign or malignant ES is not diagnostic of an eccrine neoplasm, it is helpful in elucidating the cellular differentiation and narrowing the differential diagnosis. Treatment recommendations are difficult to make because of the overall poor outcome in cases of MES. Local control should be pursued aggressively with wide excision and with particular attention paid to the margins. These tumours are unresponsive to radiotherapy and there is no known successful chemotherapy regimen.²

Eccrine poroma is a benign tumour that arises from intra epidermal portion of the sweat duct, also called acrosyringium, usually presents as a solitary, smooth, flesh-coloured lesion on the foot or hand with majority being on the palm and the palmar surface of fingers.^13,14 It was first described by Pinkus et al in 1956. When presenting their case of cystic variant of EP, Sami M Mamoun et al.,¹⁵ conducted a review of literature for the period 1956 to 1971. A total of 111 cases of EP were found, out of which there were 11 cases of hand involvement (10%), majority being on the palm and the palmar surface of fingers .Although majority of EPs are reported to occur in the extremities, the soles and sides of the foot are particularly more affected than the hand. Hyman and Brownstein presented a series of 45 cases and reviewed all the cases reported until then and found a total of 101 lesions and out off which only six were in the hand, all being in the palm.¹⁶ Both our cases were similarly on the proximal palm and the palmar surface of the ring finger. One had melanoma like pigmentation. It seems that the pigmented variant of EP is more common than the cases in the literature indicate.¹⁷ In general EPs are not pigmented, but sometimes they may be, in dark skinned persons.¹⁴

Benign tumours demonstrating features of secretory and excretory ductal cells are called eccrine acrospiromas; known by at least 16 different other names.¹⁸ The differential diagnosis of eccrine acrospiroma includes glomus tumour because of the presence of, in both entities, round clear cells and marked vascularity; the distinction between the two entities can be facilitated by immunohistochemical evaluation.¹⁹ Our case was of a nodular variety with patchy clear cell pattern. Review of English literature revealed 40 cases of eccrine acrospiroma of the hand.¹⁸ Results of Eckert et al. indicate that co expression of cytokeratin and vimentin may be frequently found in a variety of benign and malignant sweat gland tumours. However, vimentin alone is not a specific marker for myoepithelial cells, whereas a set of markers including antibodies to cytokeratin, vimentin and alpha smooth muscle actin is most reliable for demonstrating evidence of myoepithelial differentiation or myoepithelial cells within sweat gland tumours. In the majority of these neoplasms, vimentin-positive cells correspond to myoepithelial cells. As vimentin is not specific for myoepithelial cells, additional stains for alpha smooth muscle actin should be performed to prove the myoepithelial nature of vimentin-positive cells.²⁰

4 Conclusions

The rarity of sweat gland tumours of the hand prompted us to report this and to share our experience with the dedicated as well as the occasional hand surgeon. Three of our cases of eccrine spiradenoma were clinically diagnosed as glomus tumours; therefore they should be included in the differential diagnosis of glomus mimickers. We also noted that, in three patients the tumours were around the wrist. Similarly, in pigmented tumours of the hand, eccrine poroma should be considered in the clinical differential diagnosis. These sweat gland neoplasms, benign and malignant, may be more common than previously believed. These tumours cannot be confidently diagnosed on clinical examination alone. This emphasises the need to undertake early surgical measures because of the potential danger in observing undiagnosed tumours of the hand over long periods. Immunohistochemical analysis has a pivotal role to play in establishing the diagnosis of different sweat gland tumours, both malignant as well as benign. When a tumour is difficult to classify, it is imperative to differentiate between benign and malignant lesions on histological examination. Treatment of MES should be focussed, in particular, on aggressive local control of the tumour. Adjuvant treatment modalities have no established role.

Credit author statement

V.S.Patil, V.A.Malshikare and A.V. Patil has contributed for this study.

Ethical

It was approved by Ethical committee.

Funding statement

No funding received.

Patient consent

We have taken consent from Guardian/Patient.