An Asymptomatic Linear Plaque on Left Palm

A 65-year-old man presented with an asymptomatic growth on the left palm for 15 years. The lesion followed a burn injury and has been growing slowly. There was no history of bleeding or discharge from the lesion. There was no family members involved with similar condition. Clinical examination showed solitary, large, linear plaque with verrucous surface of 4 cm × 2 cm size on the hypothenar eminence of the left palm [Figure 1]. A few reddish-brown spots were seen on the surface. Hair, teeth, nail, mucous membranes, general physical examination, and systemic examination were normal. A punch biopsy was done from the plaque and histopathology revealed vertically oriented proliferation of epidermis centered around the acrosyringium [Figure 2] and delicate fibroplasias in reticular dermis [Figure 3].Figure 1: A solitary, skin-colored plaque with verrucous surface and bluish-brown spots seen on the left palmFigure 2: Vertically arranged hyperplastic epidermal proliferation centred on acrosyringium. (H and E stain, 100x)Figure 3: Epidermal projections within the mild fibroplasia in the reticular dermis. (H and E stain, 400x)What is the diagnosis? Answer Reactive eccrine syringofibradenoma Discussion Eccrine syringofibradenoma (ESFA) is a rare tumor of eccrine ductal differentiation with variable clinical features. It was first described by Mascaro in 1963 as benign adnexal neoplasm and it is considered to originate from the excretory portion of eccrine sweat gland.[1] It may present as solitary or multiple plaques and nodules in a symmetrical or linear pattern. Over 75 cases of EFSA have been reported in the literature around the world. Among them, approximately five had palm as a primary site of involvement. Common sites of involvement are the extremities, face, and trunk. Other rare sites of involvement include nails, scalp, and perianal region. It mainly affects the middle-aged to elderly patients between seventh and eighth decade. The pathogenesis is not yet clear. Repetitive damage-repair cycles causing dysregulation of epidermal growth and differentiation and increased mast cells in ESFA lesions suggest a process in wound healing and tissue remodeling. It may be reactive, representing hyperplasia to diverse stimuli or may be neoplastic usually presenting as a single lesion. This epithelial transformation could be in association with inflammatory or neoplastic disorders such as chronic skin ulcers, burn scar, erosive lichen planus, peripheral neuropathies, nevus sebaceous, and pre-existing malignant tumors like squamous cell carcinoma and porocarcinoma.[2] It has variable clinical features and characteristic histopathological findings. Based on clinical features, five subtypes have been reported; though characteristic histopathological finding is common to all subtypes. The subtypes are 1) solitary ESFA, 2) unilateral linear ESFA, 3) multiple ESFA without associated cutaneous features 4) multiple ESFA associated with hidrotic ectodermal dysplasia, and 5) reactive ESFA. Fibroepithelioma of Pinkus and squamous cell carcinoma were the differential diagnosis considered in this case before evaluation. Characteristic histopathological features of ESFA include a network of strands and cords of monomorphous epithelial cells extending down from the epidermis in a reticular pattern with eccrine duct formations embedded in a fibrovascular stroma. These long, thin epidermal projections confluence at the termination giving an appearance of crab claws. The tumor is usually limited to the papillary dermis.[3] Immunohistochemical staining for carcinoembryonic antigen and BER-Ep4 shows positivity indicating cells of ductal differentiation. Dermoscopic features of ESFA include a pinkish center surrounded by white lines, multiple superficial erosions, glomerular vessels in regular arrangement and intracorneal hemorrhage.[4] ESFA has to be differentiated histologically from eccrine poroma, squamous cell carcinoma, fibroepithelial tumor of Pinkus and pseudoepithelial hyperplasia. The clinical course of ESFA is usually benign; though malignant transformation into syringofibrocarcinoma, eccrine porocarcinoma and association with squamous cell carcinoma is seen in less than 1% as reported in the literature. Metastasis has not been reported. An increase in size, pain, ulcer and crust formation and persistent lesion even after excision would suggest malignant transformation. Malignant transformation is seen more commonly in male, elderly patients in their 7th or 8th decade, involving lower extremities. Spontaneous involution has been reported in reactive ESFA. Surgical excision is the treatment of choice for solitary and resectable lesions. Since the risk of transformation into malignancy is low, monitoring and follow up of the cases in difficult to excise areas can be done. For multiple lesions, cryotherapy, curettage, electrocautery, ablative laser therapy, photodynamic therapy, local radiotherapy, topical 5-fluorouracil, imiquimod, topical and systemic retinoids have been used with variable efficacy.[5] Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. Use of artificial intelligence (AI) The preparation of this manuscript was carried out entirely by the author without the use of artificial intelligence technologies.