Adult-Onset Subungual Eccrine Angiomatous Hamartoma on Right Great Toe: A Case Report

Eccrine angiomatous hamartoma (EAH) is an uncommon benign tumor usually presenting as a single, flesh or reddish papule or nodule1. It may be associated with hyperhidrosis or pain2. Histologically, it is composed of hyperplasia of eccrine glands in association with dilated vascular channels in the dermis2. It generally appears congenital or in childhood, rarely arising during adulthood, and mainly occurs on the distal extremities such as toes, fingers, and legs1. Herein, we describe a 52-year-old female with an adult-onset EAH lesion on the right great toenail bed as a rare case.

A 52-year-old Korean female presented with a tender, 0.3-cm-sized, brownish nodule on the right great toenail bed (Fig. 1A). The subungual nodule had been growing for 3 months. She had no history of trauma on the nodule and had no underlying disease. For removal and histopathological analysis, elliptical excisional biopsy was performed after partial avulsion of the right great toenail plate (Fig. 1B).

Fig. 1
(A) A tender, solitary nodule on the right great toenail bed of 52-year old woman (arrow). (B) A well-demarcated nodule after partial nail avulsion. We received the patient’s consent form about publishing all photographic materials.

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The biopsy specimen showed epidermal acanthosis (Fig. 2A), vascular proliferation in the superficial dermis (Fig. 2B), and proliferation of eccrine glands in the mid to deep dermis (Fig. 2C). In immunohistochemical studies, CD31, staining vascular endothelial cells, showed a positive reaction (Fig. 3A) in the area mixed with eccrine glands of mid to deep dermis, but podoplanin for staining lymphatic endothelial cells showed a negative reaction (Fig. 3B) in the same field. The nodule revealed positive reactivity with carcinoembryonic antigen (CEA) and S-100 for secretory ductal components of the glands (Fig. 3C, D). These histopathological analyses indicated origination from vascular structures, consistent with a diagnosis of EAH. At 3 months after surgery, she has recovered well and complained of no adverse effects or recurrence.

Fig. 2
Histopathological features of the lesion. (A) Scanner view showing epidermal acanthosis (H&E, ×10). (B) Proliferation of vascular structures in the superficial dermis (H&E, ×100). (C) Proliferation of eccrine sweat glands in the deep dermis (H&E, ×100).

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Fig. 3
Immunohistochemical studies of the lesion. (A) Proliferated vascular structures showing positivity for CD31 on immunohistochemistry are intermingled with eccrine glands in the mid dermis (CD31, ×200). (B) Proliferated vascular structures in the same area shows negativity for D2-40 (podoplanin) on immunohistochemistry (D2-40, ×200). (C) Eccrine glands proliferation in the deep dermis shows positivity for carcinoembryonic antigen (CEA) on immunohistochemistry (CEA, ×200). (D) Eccrine glands proliferation in the deep dermis shows positivity for S-100 on immunohistochemistry (S-100, ×200).

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In previous immunohistochemical studies of EAH, the ductal portions of the eccrine gland show positivity for S-100, CAM 2.5, and anti-CEA, while the secretory portions react positively for anti-CEA, cytokeratin and anti-EMA3. Also, for distinguishing capillaries from lymphatics, factor VIII-related antigen, CD-31, and anti-Ulex europaeus-1 are used for staining vasculatures, whereas D2-40 (podoplanin) is used for staining lymphatic vessels. In our case, when we stained the specimen, it showed positivity for staining vascular components using CD-31, and negativity for staining lymphatic components using D2-40. It means that the proliferated channels have the characteristics of vessels rather than lymphatics, and eventually they originated from vessels. Mitosis or cellular atypia was not observed.

A previous study reviewed 68 EAH cases in the PubMed database from 1968 and 2018, 47 of which (69.0%) showed lesions on the distal extremities, and 50 of which (73.5%) were reported to be congenital4. In a review by Patterson et al.1, 12 of 18 cases (66.7%) were located on the extremities, with the rest on the trunk and head/neck. There were 2 previously reported EAH cases with accompanying nail deformity. One case was a 22-month-old girl presenting with a reddish nodule with nail deformity on the fifth toe of her left foot5. The other case was a 37-year-old female who had nodules on the left hand and right foot that had been present since childhood and that caused nail deformity, leaving vestigial nails6. It is unclear whether these cases involved lesions under the nails, and we assume that these lesions had developed next to the nail or in the nail matrix.

Our presented case is adult-onset EAH that occurred as a subungual lesion. Unlike the previous cases, it did not cause nail deformity or destruction and initially was misinterpreted as some other subungual tender nodule. The differential diagnosis of a subungual nodule includes benign solid tumors such as glomus tumor, lobular capillary hemangioma, angiokeratoma, angiomyomatous hamartoma nevus, and malignant tumors7, 8. Herein, to the best of our knowledge, we report the first case of subungual adult-onset EAH without nail deformity. Based on this case, we can consider EAH additionally when discriminating painful subungual nodules.